Prof. Dr. Marc Alexa

@article{Akalin:2024:MPIT,
author = {Akalin, Koray and Finnendahl, Ugo and Sorkine-Hornung, Olga and Alexa, Marc},
title = {Mesh Parameterization Meets Intrinsic Triangulations},
journal = {Computer Graphics Forum},
volume = {43},
number = {5},
pages = {e15134},
keywords = {CCS Concepts, • Computing methodologies → Computer graphics, Mesh models, Mesh geometry models},
doi = {https://doi.org/10.1111/cgf.15134},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/cgf.15134},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/cgf.15134},
abstract = {A parameterization of a triangle mesh is a realization in the plane so that all triangles have positive signed area. Triangle mesh parameterizations are commonly computed by minimizing a distortion energy, measuring the distortions of the triangles as they are mapped into the parameter domain. It is assumed that the triangulation is fixed and the triangles are mapped affinely. We consider a more general setup and additionally optimize among the intrinsic triangulations of the piecewise linear input geometry. This means the distortion energy is computed for the same geometry, yet the space of possible parameterizations is enlarged. For minimizing the distortion energy, we suggest alternating between varying the parameter locations of the vertices and intrinsic flipping. We show that this process improves the mapping for different distortion energies at moderate additional cost. We also find intrinsic triangulations that are better starting points for the optimization of positions, offering a compromise between the full optimization approach and exploiting the additional freedom of intrinsic triangulations.},
year = {2024}
}

@InProceedings{Dogadov:2024:Flats,
    author    = {Dogadov, Gabriel and Finnendahl, Ugo and Alexa, Marc},
    title     = {Fitting Flats to Flats},
    booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
    month     = {June},
    year      = {2024}
}

@article{Bunge:2024:PLMR,
author = {Bunge, Astrid and Bukenberger, Dennis R. and Wagner, Sven D. and Alexa, Marc and Botsch, Mario},
title = {Polygon Laplacian Made Robust},
journal = {Computer Graphics Forum},
volume = {43},
number = {2},
pages = {e15025},
keywords = {Mesh geometry models, Mesh generation, Discretization},
doi = {https://doi.org/10.1111/cgf.15025},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/cgf.15025},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/cgf.15025},
abstract = {Abstract Discrete Laplacians are the basis for various tasks in geometry processing. While the most desirable properties of the discretization invariably lead to the so-called cotangent Laplacian for triangle meshes, applying the same principles to polygon Laplacians leaves degrees of freedom in their construction. From linear finite elements it is well-known how the shape of triangles affects both the error and the operator's condition. We notice that shape quality can be encapsulated as the trace of the Laplacian and suggest that trace minimization is a helpful tool to improve numerical behavior. We apply this observation to the polygon Laplacian constructed from a virtual triangulation [BHKB20] to derive optimal parameters per polygon. Moreover, we devise a smoothing approach for the vertices of a polygon mesh to minimize the trace. We analyze the properties of the optimized discrete operators and show their superiority over generic parameter selection in theory and through various experiments.},
year = {2024}
}

@article{10.1145/3618383,
author = {Djuren, Tobias and Kohlbrenner, Maximilian and Alexa, Marc},
title = {K-Surfaces: B\'{e}zier-Splines Interpolating at Gaussian Curvature Extrema},
year = {2023},
issue_date = {December 2023},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
volume = {42},
number = {6},
issn = {0730-0301},
url = {https://doi.org/10.1145/3618383},
doi = {10.1145/3618383},
journal = {ACM Trans. Graph.},
month = {dec},
articleno = {210},
numpages = {13},
keywords = {interactive surface modeling, b\'{e}zier patches, gaussian curvature, b\'{e}zier splines}
}

@article{Worchel:2023:DRPG,
author = {Worchel, Markus and Alexa, Marc},
title = {Differentiable Rendering of Parametric Geometry},
year = {2023},
issue_date = {December 2023},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
volume = {42},
number = {6},
issn = {0730-0301},
url = {https://doi.org/10.1145/3618387},
doi = {10.1145/3618387},
abstract = {We propose an efficient method for differentiable rendering of parametric surfaces and curves, which enables their use in inverse graphics problems. Our central observation is that a representative triangle mesh can be extracted from a continuous parametric object in a differentiable and efficient way. We derive differentiable meshing operators for surfaces and curves that provide varying levels of approximation granularity. With triangle mesh approximations, we can readily leverage existing machinery for differentiable mesh rendering to handle parametric geometry. Naively combining differentiable tessellation with inverse graphics settings lacks robustness and is prone to reaching undesirable local minima. To this end, we draw a connection between our setting and the optimization of triangle meshes in inverse graphics and present a set of optimization techniques, including regularizations and coarse-to-fine schemes. We show the viability and efficiency of our method in a set of image-based computer-aided design applications.},
journal = {ACM Trans. Graph.},
month = {dec},
articleno = {232},
numpages = {18},
keywords = {differentiable rendering, geometry reconstruction}
}

@article{10.1145/3592445,
author = {Finnendahl, Ugo and Bogiokas, Dimitrios and Robles Cervantes, Pablo and Alexa, Marc},
title = {Efficient Embeddings in Exact Arithmetic},
year = {2023},
issue_date = {August 2023},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
volume = {42},
number = {4},
issn = {0730-0301},
url = {https://doi.org/10.1145/3592445},
doi = {10.1145/3592445},
abstract = {We provide a set of tools for generating planar embeddings of triangulated topological spheres. The algorithms make use of Schnyder labelings and realizers. A new representation of the realizer based on dual trees leads to a simple linear time algorithm mapping from weights per triangle to barycentric coordinates and, more importantly, also in the reverse direction. The algorithms can be implemented so that all coefficients involved are 1 or -1. This enables integer computation, making all computations exact. Being a Schnyder realizer, mapping from positive triangle weights guarantees that the barycentric coordinates form an embedding. The reverse direction enables an algorithm for fixing flipped triangles in planar realizations, by mapping from coordinates to weights and adjusting the weights (without forcing them to be positive). In a range of experiments, we demonstrate that all algorithms are orders of magnitude faster than existing robust approaches.},
journal = {ACM Trans. Graph.},
month = {jul},
articleno = {71},
numpages = {17},
keywords = {integer coordinates, parametrization, schnyder labeling}
}

@article{https://doi.org/10.1111/cgf.14907,
author = {Kohlbrenner, M. and Lee, S. and Alexa, M. and Kazhdan, M.},
title = {Poisson Manifold Reconstruction — Beyond Co-dimension One},
journal = {Computer Graphics Forum},
volume = {42},
number = {5},
pages = {e14907},
keywords = {CCS Concepts, • Computing methodologies → Shape modeling, • Mathematics of computing → Nonlinear equations, Numerical analysis, curve and surface reconstruction, sub-manifold reconstruction, exterior product, polynomial optimization},
doi = {https://doi.org/10.1111/cgf.14907},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/cgf.14907},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/cgf.14907},
abstract = {Abstract Screened Poisson Surface Reconstruction creates 2D surfaces from sets of oriented points in 3D (and can be extended to co-dimension one surfaces in arbitrary dimensions). In this work we generalize the technique to manifolds of co-dimension larger than one. The reconstruction problem consists of finding a vector-valued function whose zero set approximates the input points. We argue that the right extension of screened Poisson Surface Reconstruction is based on exterior products: the orientation of the point samples is encoded as the exterior product of the local normal frame. The goal is to find a set of scalar functions such that the exterior product of their gradients matches the exterior products prescribed by the input points. We show that this setup reduces to the standard formulation for co-dimension 1, and leads to more challenging multi-quadratic optimization problems in higher co-dimension. We explicitly treat the case of co-dimension 2, i.e., curves in 3D and 2D surfaces in 4D. We show that the resulting bi-quadratic problem can be relaxed to a set of quadratic problems in two variables and that the solution can be made effective and efficient by leveraging a hierarchical approach.},
year = {2023}
}

@inproceedings{worchel:2023:diff_shadow,
	title = {Differentiable Shadow Mapping for Efficient Inverse Graphics},
	author = {Markus Worchel and Marc Alexa},
	url = {https://openaccess.thecvf.com/content/CVPR2023/html/Worchel_Differentiable_Shadow_Mapping_for_Efficient_Inverse_Graphics_CVPR_2023_paper.html, CVF Open Access Version
https://mworchel.github.io/differentiable-shadow-mapping/, Project Page
https://github.com/mworchel/differentiable-shadow-mapping, Code},
	year = {2023},
	date = {2023-06-01},
	booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
	pages = {142-153},
	abstract = {We show how shadows can be efficiently generated in differentiable rendering of triangle meshes. Our central observation is that pre-filtered shadow mapping, a technique for approximating shadows based on rendering from the perspective of a light, can be combined with existing differentiable rasterizers to yield differentiable visibility information. We demonstrate at several inverse graphics problems that differentiable shadow maps are orders of magnitude faster than differentiable light transport simulation with similar accuracy -- while differentiable rasterization without shadows often fails to converge. },
	keywords = {computer graphics, differentiable rendering, machine learning, neural rendering},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Finnendahl:2023:AR,
author = {Finnendahl, Ugo and Schwartz, Matthias and Alexa, Marc},
title = {ARAP Revisited: Discretizing the Elastic Energy using Intrinsic Voronoi Cells},
journal = {Computer Graphics Forum},
year={2023},
volume = {43},
number = {5},
pages = {e15134},
keywords = {modelling, deformations, polygonal modelling},
doi = {https://doi.org/10.1111/cgf.14790},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/cgf.14790},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/cgf.14790},
abstract = {Abstract As-rigid-as-possible (ARAP) surface modelling is widely used for interactive deformation of triangle meshes. We show that ARAP can be interpreted as minimizing a discretization of an elastic energy based on non-conforming elements defined over dual orthogonal cells of the mesh. Using the intrinsic Voronoi cells rather than an orthogonal dual of the extrinsic mesh guarantees that the energy is non-negative over each cell. We represent the intrinsic Delaunay edges extrinsically as polylines over the mesh, encoded in barycentric coordinates relative to the mesh vertices. This modification of the original ARAP energy, which we term iARAP, remedies problems stemming from non-Delaunay edges in the original approach. Unlike the spokes-and-rims version of the ARAP approach it is less susceptible to the triangulation of the surface. We provide examples of deformations generated with iARAP and contrast them with other versions of ARAP. We also discuss the properties of the Laplace-Beltrami operator implicitly introduced with the new discretization.}
}

@article{Alexa:2024:TE,
	abstract = {Tutte's embedding theorem states that every 3-connected graph without a {\$}{\$}K{\_}5{\$}{\$}- or {\$}{\$}K{\_}{\{}3,3{\}}{\$}{\$}-minor (i.e., a planar graph) is embedded in the plane if the outer face is in convex position and the interior vertices are convex combinations of their neighbors. We show that this result extends to simply connected tetrahedral meshes in a natural way: for the tetrahedral mesh to be embedded if the outer polyhedron is in convex position and the interior vertices are convex combination of their neighbors it is sufficient (but not necessary) that the graph of the tetrahedral mesh contains no {\$}{\$}K{\_}6{\$}{\$}and no {\$}{\$}K{\_}{\{}3,3,1{\}}{\$}{\$}, and all triangles incident on three boundary vertices are boundary triangles.},
	author = {Alexa, Marc},
	date = {2023/03/17},
	doi = {10.1007/s00454-023-00494-0},
	isbn = {1432-0444},
	journal = {Discrete \& Computational Geometry},
	title = {Tutte Embeddings of Tetrahedral Meshes},
	url = {https://doi.org/10.1007/s00454-023-00494-0},
	year = {2023}
}

@inproceedings{alexa:2022:alpha_functions,
	title = {$\alpha$-Functions: Piecewise-linear Approximation from Noisy and Hermite Data},
	author = {Marc Alexa},
	url = {https://dl.acm.org/doi/abs/10.1145/3528233.3530743},
doi = {10.1145/3528233.3530743},
	year = {2022},
	date = {2022-07-27},
	booktitle = {ACM SIGGRAPH 2022 Conference Proceedings},
	pages = {1-9},
	abstract = {We introduce α-functions, providing piecewise linear approximation to given data as the difference of two convex functions. The parameter α controls the shape of a paraboloid that is probing the data and may be used to filter out noise in the data. The use of convex functions enables tools for efficient approximation to the data, adding robustness to outliers, and dealing with gradient information. It also allows using the approach in higher dimension. We show that α-functions can be efficiently computed and demonstrate their versatility at the example of surface reconstruction from noisy surface samples.},
	keywords = {computer graphics, geometry processing},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:2022:SFS,
	title = {Super-Fibonacci Spirals: Fast, Low-Discrepancy Sampling of SO(3)},
	author = {Marc Alexa},
	url = {https://openaccess.thecvf.com/content/CVPR2022/html/Alexa_Super-Fibonacci_Spirals_Fast_Low-Discrepancy_Sampling_of_SO3_CVPR_2022_paper.html, CVF Open Access Version
https://marcalexa.github.io/superfibonacci/, Project on Github},
	year = {2022},
	date = {2022-06-01},
	booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
	pages = {8291-8300},
	abstract = {Super-Fibonacci spirals are an extension of Fibonacci spirals, enabling fast generation of an arbitrary but fixed number of 3D orientations. The algorithm is simple and fast. A comprehensive evaluation comparing to other methods shows that the generated sets of orientations have low discrepancy, minimal spurious components in the power spectrum, and almost identical Voronoi volumes. This makes them useful for a variety of applications in vision, robotics, machine learning, and in particular Monte Carlo sampling.},
	keywords = {scientific computing},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@incollection{Koch:2021:HDA,
	title = {Hardware Design and Accurate Simulation of Structured-Light Scanning for Benchmarking of 3D Reconstruction Algorithms},
	author = {Sebastian Koch and Yurii Piadyk and Markus Worchel and Marc Alexa and Claudio Silva and Denis Zorin and Daniele Panozzo},
	url = {https://geometryprocessing.github.io/scanner-sim, Project Page},
	year = {2021},
	date = {2021-10-10},
	booktitle = {Thirty-fifth Conference on Neural Information Processing Systems (NeurIPS 2021)},
	issuetitle = {Datasets and Benchmarks Track},
	abstract = {Images of a real scene taken with a camera commonly differ from synthetic images of a virtual replica of the same scene, despite advances in light transport simulation and calibration. By explicitly co-developing the Structured-Light Scanning (SLS) hardware and rendering pipeline we are able to achieve negligible per-pixel difference between the real image and the synthesized image on geometrically complex calibration objects with known material properties. This approach provides an ideal test-bed for developing and evaluating data-driven algorithms in the area of 3D reconstruction, as the synthetic data is indistinguishable from real data and can be generated at large scale by simulation. We propose three benchmark challenges using a combination of acquired and synthetic data generated with our system: (1) a denoising benchmark tailored to structured-light scanning, (2) a shape completion benchmark to fill in missing data, and (3) a benchmark for surface reconstruction from dense point clouds. Besides, we provide a large collection of high-resolution scans that allow to use our system and benchmarks without reproduction of the hardware setup on our website},
	howpublished = {https://openreview.net/forum?id=bNL5VlTfe3p},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {incollection}
}

@article{Bunge:DL:2021,
	title = {The Diamond Laplace for Polygonal and Polyhedral Meshes},
	author = {Astrid Bunge and Mario Botsch and Marc Alexa},
	url = {https://www.youtube.com/watch?v=i7mYiJSG2ss, Talk (YouTube)},
	doi = {10.1111/cgf.14369},
	year = {2021},
	date = {2021-08-23},
	journal = {Computer Graphics Forum},
	volume = {40},
	number = {5},
	pages = {217-230},
	abstract = {We introduce a construction for discrete gradient operators that can be directly applied to arbitrary polygonal surface as well as polyhedral volume meshes. The main idea is to associate the gradient of functions defined at vertices of the mesh with diamonds: the region spanned by a dual edge together with its corresponding primal element — an edge for surface meshes and a face for volumetric meshes. We call the operator resulting from taking the divergence of the gradient Diamond Laplacian. Additional vertices used for the construction are represented as affine combinations of the original vertices, so that the Laplacian operator maps from values at vertices to values at vertices, as is common in geometry processing applications. The construction is local, exactly the same for all types of meshes, and results in a symmetric negative definite operator with linear precision. We show that the accuracy of the Diamond Laplacian is similar or better compared to other discretizations. The greater versatility and generally good behavior come at the expense of an increase in the number of non-zero coefficients that depends on the degree of the mesh elements.},
	keywords = {computer graphics, geometry processing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Kohlbrenner2021,
	title = {Gauss Stylization: Interactive Artistic Mesh Modeling based on Preferred Surface Normals},
	author = {Max Kohlbrenner and Ugo Finnendahl and Tobias Djuren and Marc Alexa},
	url = {https://cybertron.cg.tu-berlin.de/projects/gaussStylization/},
	doi = {https://doi.org/10.1111/cgf.14355},
	year = {2021},
	date = {2021-08-23},
	journal = {Computer Graphics Forum},
	volume = {40},
	number = {5},
	pages = {33-43},
	abstract = {Abstract Extending the ARAP energy with a term that depends on the face normal, energy minimization becomes an effective stylization tool for shapes represented as meshes. Our approach generalizes the possibilities of Cubic Stylization: the set of preferred normals can be chosen arbitrarily from the Gauss sphere, including semi-discrete sets to model preference for cylinder- or cone-like shapes. The optimization is designed to retain, similar to ARAP, the constant linear system in the global optimization. This leads to convergence behavior that enables interactive control over the parameters of the optimization. We provide various examples demonstrating the simplicity and versatility of the approach.},
	keywords = {computer graphics, geometric stylization, geometry processing, non-photorealistic rendering, shape modeling},
	pubstate = {published},
	tppubtype = {article}
}

@article{Zhang:FRA:2021,
	title = {Fast Updates for Least-Squares Rotational Alignment},
	author = {Jiayi Eris Zhang and Alec Jacobson and Marc Alexa},
	url = {https://www.dgp.toronto.edu/projects/fast-rotation-fitting/, Project Page},
	doi = {10.1111/cgf.142611},
	year = {2021},
	date = {2021-06-04},
	journal = {Computer Graphics Forum},
	volume = {40},
	number = {2},
	pages = {12-22},
	abstract = {Across computer graphics, vision, robotics and simulation, many applications rely on determining the 3D rotation that aligns two objects or sets of points. The standard solution is to use singular value decomposition (SVD), where the optimal rotation is recovered as the product of the singular vectors. Faster computation of only the rotation is possible using suitable parameterizations of the rotations and iterative optimization. We propose such a method based on the Cayley transformations. The resulting optimization problem allows better local quadratic approximation compared to the Taylor approximation of the exponential map. This results in both faster convergence as well as more stable approximation compared to other iterative approaches. It also maps well to AVX vectorization. We compare our implementation with a wide range of alternatives on real and synthetic data. The results demonstrate up to two orders of magnitude of speedup compared to a straightforward SVD implementation and a 1.5-6 times speedup over popular optimized code.},
	keywords = {computer graphics, geometric mechanics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:PC:2021,
	title = {PolyCover: Shape Approximating With Discrete Surface Orientation},
	author = {Marc Alexa},
	doi = {10.1109/MCG.2021.3060946},
	issn = {0272-1716},
	year = {2021},
	date = {2021-02-22},
	journal = {IEEE Computer Graphics and Applications},
	volume = {41},
	number = {3},
	pages = {85-95},
	abstract = {We consider the problem of approximating given shapes so that the surface normals are restricted to a prescribed discrete set. Such shape approximations are commonly required in the context of manufacturing shapes. We provide an algorithm that first computes maximal interior polytopes and, then, selects a subset of offsets from the interior polytopes that cover the shape. This provides prescribed Hausdorff error approximations that use only a small number of primitives.},
	keywords = {computer graphics, geometry processing, shape approximation},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:CWD:2020,
	title = {Conforming Weighted Delaunay Triangulation},
	author = {Marc Alexa},
	url = {https://www.cg.tu-berlin.de/research/projects/cwdt/, Project page
https://dl.acm.org/doi/10.1145/3414685.3417776?cid=81100235480, ACM-authorized paper},
	doi = {10.1145/3414685.3417776},
	year = {2020},
	date = {2020-12-06},
	journal = {ACM Transactions on Graphics},
	volume = {39},
	number = {6},
	pages = {248},
	abstract = {Given a set of points together with a set of simplices
we show how to compute weights associated with the points such that the weighted Delaunay triangulation of the point set contains the simplices, if possible. For a given triangulated surface, this process provides a tetrahedral mesh conforming to the triangulation, i.e. solves the problem of meshing the triangulated surface without inserting additional vertices. The restriction to weighted Delaunay triangulations ensures that the orthogonal dual mesh is embedded, facilitating common geometry processing tasks.

We show that the existence of a single simplex in a weighted Delaunay triangulation for given vertices amounts to a set of linear inequalities, one for each vertex. This means that the number of inequalities for a given triangle mesh is quadratic in the number of mesh elements, making the naive approach impractical. We devise an algorithm that incrementally selects a small subset of inequalities, repeatedly updating the weights, until the weighted Delaunay triangulation contains all constrained simplices or the problem becomes infeasible. Applying this algorithm to a range of triangle meshes commonly used graphics demonstrates that many of them admit a conforming weighted Delaunay triangulation, in contrast to conforming or constrained Delaunay that require additional vertices to split the input primitives.},
	keywords = {computer graphics, geometry processing, laplacian},
	pubstate = {published},
	tppubtype = {article}
}

@article{Wang:2020:CD,
	title = {Computational discrimination between natural images based on gaze during mental imagery},
	author = {Xi Wang and Andreas Ley and Sebastian Koch and James Hays and Kenneth Holmqvist and Marc Alexa},
	url = {https://rdcu.be/b6tel, Article
http://cybertron.cg.tu-berlin.de/xiwang/mental_imagery/retrieval.html, Related Project},
	doi = {10.1038/s41598-020-69807-0},
	issn = {2045-2322},
	year = {2020},
	date = {2020-08-03},
	journal = {Scientific Reports},
	volume = {10},
	pages = {13035},
	abstract = {When retrieving image from memory, humans usually move their eyes spontaneously as if the image were in front of them. Such eye movements correlate strongly with the spatial layout of the recalled image content and function as memory cues facilitating the retrieval procedure. However, how close the correlation is between imagery eye movements and the eye movements while looking at the original image is unclear so far. In this work we first quantify the similarity of eye movements between recalling an image and encoding the same image, followed by the investigation on whether comparing such pairs of eye movements can be used for computational image retrieval. Our results show that computational image retrieval based on eye movements during spontaneous imagery is feasible. Furthermore, we show that such a retrieval approach can be generalized to unseen images.},
	keywords = {HCI, mental imagery, Visual attention},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2020:PLO,
	title = {Properties of Laplace Operators for Tetrahedral Meshes},
	author = {Marc Alexa and Philipp Herholz and Maximilian Kohlbrenner and Olga Sorkine},
	url = {https://igl.ethz.ch/projects/LB3D/, Project Page},
	doi = {10.1111/cgf.14068},
	year = {2020},
	date = {2020-07-06},
	journal = {Computer Graphics Forum},
	volume = {39},
	number = {5},
	pages = {55-68},
	abstract = {Discrete Laplacians for triangle meshes are a fundamental tool in geometry processing. The so-called cotan Laplacian is widely used since it preserves several important properties of its smooth counterpart. It can be derived from different principles: either considering the piecewise linear nature of the primal elements or associating values to the dual vertices. Both approaches lead to the same operator in the two-dimensional setting. In contrast, for tetrahedral meshes, only the primal construction is reminiscent of the cotan weights, involving dihedral angles. We provide explicit formulas for the lesser-known dual construction. In both cases, the weights can be computed by adding the contributions of individual tetrahedra to an edge. The resulting two different discrete Laplacians for tetrahedral meshes only retain some of the properties of their two-dimensional counterpart. In particular, while both constructions have linear precision, only the primal construction is positive semi-definite and only the dual construction generates positive weights and provides a maximum principle for Delaunay meshes. We perform a range of numerical experiments that highlight the benefits and limitations of the two constructions for different problems and meshes.},
	keywords = {computer graphics, geometry processing, laplacian},
	pubstate = {published},
	tppubtype = {article}
}

@article{DynamicRendering,
	title = {Keep It Simple: Depth-based Dynamic Adjustment of Rendering for Head-mounted Displays Decreases Visual Comfort},
	author = {Jochen Jacobs and Xi Wang and Marc Alexa},
	url = {https://dl.acm.org/citation.cfm?id=3353902, Article 
https://dl.acm.org/authorize?N682026, ACM Authorized Paper
},
	doi = {10.1145/3353902},
	year = {2019},
	date = {2019-09-09},
	journal = {ACM Trans. Appl. Percept. },
	volume = {16},
	number = {3},
	pages = {16},
	abstract = {Head-mounted displays cause discomfort. This is commonly attributed to conflicting depth cues, most prominently between vergence, which is consistent with object depth, and accommodation, which is adjusted to the near eye displays.

It is possible to adjust the camera parameters, specifically interocular distance and vergence angles, for rendering the virtual environment to minimize this conflict. This requires dynamic adjustment of the parameters based on object depth. In an experiment based on a visual search task, we evaluate how dynamic adjustment affects visual comfort compared to fixed camera parameters. We collect objective as well as subjective data. Results show that dynamic adjustment decreases common objective measures of visual comfort such as pupil diameter and blink rate by a statistically significant margin. The subjective evaluation of categories such as fatigue or eye irritation shows a similar trend but was inconclusive. This suggests that rendering with fixed camera parameters is the better choice for head-mounted displays, at least in scenarios similar to the ones used here.},
	keywords = {dynamic rendering, vergence, Virtual reality},
	pubstate = {published},
	tppubtype = {article}
}

@article{jemr2019,
	title = {The mean point of vergence is biased under projection},
	author = {Xi Wang and Kenneth Holmqvist and Marc Alexa},
	url = {https://bop.unibe.ch/JEMR/article/view/JEMR.12.4.2},
	doi = {https://doi.org/10.16910/jemr.12.4.2},
	issn = {1995-8692},
	year = {2019},
	date = {2019-09-09},
	journal = {Journal of Eye Movement Research},
	volume = {12},
	number = {4},
	abstract = {The point of interest in three-dimensional space in eye tracking is often computed based on intersecting the lines of sight with geometry, or finding the point closest to the two lines of sight. We first start by theoretical analysis with synthetic simulations. We show that the mean point of vergence is generally biased for centrally symmetric errors and that the bias depends on the horizontal vs. vertical error distribution of the tracked eye positions. Our analysis continues with an evaluation on real experimental data. The error distributions seem to be different among individuals but they generally leads to the same bias towards the observer. And it tends to be larger with an increased viewing distance. We also provided a recipe to minimize the bias, which applies to general computations of eye ray intersection. These findings not only have implications for choosing the calibration method in eye tracking experiments and interpreting the observed eye movements data; but also suggest to us that we shall consider the mathematical models of calibration as part of the experiment.},
	keywords = {eye tracking, vergence},
	pubstate = {published},
	tppubtype = {article}
}

@misc{ecem19,
	title = {Computational discrimination between natural images based on gaze during mental imagery},
	author = {Xi Wang and Kenneth Holmqvist and Marc Alexa},
	url = {http://ecem2019.com/media/attachments/2019/08/27/ecem_abstract_book_updated.pdf},
	year = {2019},
	date = {2019-08-18},
	abstract = {The term “looking-at-nothing” describes the phenomenon that humans move their eyes when looking in front of an empty space. Previous studies showed that eye movements during mental imagery while looking to nothing play a functional role in memory retrieval. However, they are not a reinstatement of the eye movements while looking at the visual stimuli and are generally distorted due to the lack of reference in front of an empty space. So far it remains unclear what the degree of similarity is between eye movements during encoding and eye movements during recall.

We studied the mental imagery eye movements while looking at nothing in a lab-controlled experiment. 100 natural images were viewed and recalled by 28 observers, following the standard looking-at-nothing paradigm. We compared the basic characteristics of eye movements during both encoding and recall. Furthermore, we studies the similarity of eye movements between two conditions by asking the question: how visual imagery eye movements can be employed for computational image retrieval. Our results showed that gaze patterns in both conditions can be used to retrieve the corresponding visual stimuli. By utilizing the similarity between gaze patterns during encoding and those during recall, we showed that it is possible to generalize to new images. This study quantitatively compared the similarity between eye movements during looking at the images and those during recall them, and offers a solid method for future studies on the looking-at-nothing phenomenon. },
	howpublished = {Presented at 20th European Conference on Eye Morvements (ECEM)},
	keywords = {eye tracking, image retrieval, mental imagery},
	pubstate = {published},
	tppubtype = {misc}
}

@article{Etienne:2019:CS,
	title = {CurviSlicer: slightly curved slicing for 3-axis printers},
	author = {Jimmy Etienne and Nicolas Ray and Daniele Panozzo and Samuel Hornus and Charlie C. L. Wang and Jonas Martinez and Sara McMains and Marc Alexa and Brian Wyvill and Sylvain Lefebvre},
	url = {https://dl.acm.org/authorize?N681473, ACM Authorized Article
},
	doi = {10.1145/3306346.3323022},
	year = {2019},
	date = {2019-07-04},
	journal = {ACM Transactions on Graphics},
	volume = {38},
	number = {4},
	abstract = {Most additive manufacturing processes fabricate objects by stacking planar layers of solidified material. As a result, produced parts exhibit a so-called staircase effect, which results from sampling slanted surfaces with parallel planes. Using thinner slices reduces this effect, but it always remains visible where layers almost align with the input surfaces.
In this research we exploit the ability of some additive manufacturing processes to deposit material slightly out of plane to dramatically reduce these artifacts. We focus in particular on the widespread Fused Filament Fabrication (FFF) technology, since most printers in this category can deposit along slightly curved paths, under deposition slope and thickness constraints.
Our algorithm curves the layers, making them either follow the natural slope of the input surface or on the contrary, make them intersect the surfaces at a steeper angle thereby improving the sampling quality. Rather than directly computing curved layers, our algorithm optimizes for a deformation of the model which is then sliced with a standard planar approach. We demonstrate that this approach enables us to encode all fabrication constraints, including the guarantee of generating collision-free toolpaths, in a convex optimization that can be solved using a QP solver.
We produce a variety of models and compare print quality between curved deposition and planar slicing.},
	keywords = {Digital manufacturing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2019:HT,
	title = {Harmonic Triangulations},
	author = {Marc Alexa},
	url = {https://www.cg.tu-berlin.de/harmonic-triangulations/, Project Page
https://dl.acm.org/authorize?N688246, ACM Authorized Paper},
	doi = {10.1145/3306346.3322986},
	year = {2019},
	date = {2019-07-03},
	journal = {ACM Transactions on Graphics},
	volume = {38},
	number = {4},
	pages = {54},
	abstract = {We introduce the notion of harmonic triangulations: a harmonic triangulation simultaneously minimizes the Dirichlet energy of all piecewise linear functions. By a famous result of Rippa, Delaunay triangulations are the harmonic triangulations of planar point sets. We prove by explicit counterexample that in 3D a harmonic triangulation does not exist in general. However, we show that bistellar flips are harmonic: if they decrease Dirichlet energy for one set of function values, they do so for all. This observation gives rise to the notion of locally harmonic triangulations. We demonstrate that locally harmonic triangulations can be efficiently computed, and efficiently reduce sliver tetrahedra. The notion of harmonic triangulation also gives rise to a scalar measure of the quality of a triangulation, which can be used to prioritize flips and optimize the position of vertices. Tetrahedral meshes generated by optimizing this function generally show better quality than Delaunay-based optimization techniques. },
	keywords = {computer graphics geometry},
	pubstate = {published},
	tppubtype = {article}
}

@conference{mentalImg,
	title = {The Mental Image Revealed by Gaze Tracking},
	author = {Xi Wang and Andreas Ley and Sebastian Koch and David Lindlbauer and James Hays and Kenneth Holmqvist and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/xiwang/mental_imagery/retrieval.html, Project page
https://dl.acm.org/authorize?N681045, ACM Authorized Paper
},
	doi = {10.1145/3290605.3300839},
	isbn = {978-1-4503-5970-2},
	year = {2019},
	date = {2019-05-04},
	booktitle = {Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems (CHI '19)
},
	publisher = {ACM},
	abstract = {Humans involuntarily move their eyes when retrieving an image from memory. This motion is often similar to actually observing the image. We suggest to exploit this behavior as a new modality in human computer interaction, using the motion of the eyes as a descriptor of the image. Interaction requires the user's eyes to be tracked but no voluntary physical activity. We perform a controlled experiment and develop matching techniques using machine learning to investigate if images can be discriminated based on the gaze patterns recorded while users merely think about image. Our results indicate that image retrieval is possible with an accuracy significantly above chance. We also show that this result generalizes to images not used during training of the classifier and extends to uncontrolled settings in a realistic scenario.},
	keywords = {eye tracking, image retrieval},
	pubstate = {published},
	tppubtype = {conference}
}

@conference{Ion:UMM:2019,
	title = {Understanding Metamaterial Mechanisms},
	author = {Alexandra Ion and David Lindlbauer and Philipp Herholz and Marc Alexa and Patrick Baudisch},
	url = {https://dl.acm.org/authorize?N681474, ACM Authorized Paper},
	doi = {10.1145/3290605.3300877},
	year = {2019},
	date = {2019-05-01},
	booktitle = {Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems (CHI '19)},
	publisher = {ACM},
	abstract = {In this paper, we establish the underlying foundations of mechanisms that are composed of cell structures---known as metamaterial mechanisms. Such metamaterial mechanisms were previously shown to implement complete mechanisms in the cell structure of a 3D printed material, without the need for assembly. However, their design is highly challenging. A mechanism consists of many cells that are interconnected and impose constraints on each other. This leads to unobvious and non-linear behavior of the mechanism, which impedes user design. In this work, we investigate the underlying topological constraints of such cell structures and their influence on the resulting mechanism. Based on these findings, we contribute a computational design tool that automatically creates a metamaterial mechanism from user-defined motion paths. This tool is only feasible because our novel abstract representation of the global constraints highly reduces the search space of possible cell arrangements.},
	keywords = {Digital manufacturing, fabrication},
	pubstate = {published},
	tppubtype = {conference}
}

@conference{Koch:2019:ABC,
	title = {ABC: A Big CAD Model Dataset for Geometric Deep Learning},
	author = {Sebastian Koch and Albert Matveev and Zhongshi Jiang and Francis Williams Alexey Artemov and Evgeny Burnaev and Marc Alexa and Denis Zorin and Daniele Panozzo},
	url = {http://openaccess.thecvf.com/content_CVPR_2019/html/Koch_ABC_A_Big_CAD_Model_Dataset_for_Geometric_Deep_Learning_CVPR_2019_paper.html, Article at CVF},
	year = {2019},
	date = {2019-05-01},
	booktitle = {Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition},
	pages = {9601--9611},
	publisher = {IEEE},
	abstract = {We introduce ABC-Dataset, a collection of one million Computer-Aided Design (CAD) models for research of geometric deep learning methods and applications. Each model is a collection of explicitly parametrized curves and surfaces, providing ground truth for differential quantities, patch segmentation, geometric feature detection, and shape reconstruction. Sampling the parametric descriptions of surfaces and curves allows generating data in different formats and resolutions, enabling fair comparisons for a wide range of geometric learning algorithms. As a use case for our dataset, we perform a large-scale benchmark for estimation of surface normals, comparing existing data driven methods and evaluating their performance against both the ground truth and traditional normal estimation methods.},
	keywords = {Digital manufacturing, geometry processing, polygonal meshes, shape retrieval},
	pubstate = {published},
	tppubtype = {conference}
}

@article{Herholz:2019:CGF,
	title = {Efficient Computation of Smoothed Exponential Maps},
	author = {Philipp Herholz and Marc Alexa},
	doi = {10.1111/cgf.13607},
	year = {2019},
	date = {2019-03-14},
	journal = {Computer Graphics Forum},
	volume = {38},
	pages = {79--90},
	abstract = {Many applications in geometry processing require the computation of local parameterizations on a surface mesh at interactive rates. A popular approach is to compute local exponential maps, i.e. parameterizations that preserve distance and angle to the origin of the map. We extend the computation of geodesic distance by heat diffusion to also determine angular information for the geodesic curves. This approach has two important benefits compared to fast approximate as well as exact forward tracing of the distance function: First, it allows generating smoother maps, avoiding discontinuities. Second, exploiting the factorization of the global Laplace–Beltrami operator of the mesh and using recent localized solution techniques, the computation is more efficient even compared to fast approximate solutions based on Dijkstra's algorithm.},
	keywords = {geometry processing},
	pubstate = {published},
	tppubtype = {article}
}

@online{concentricCircles,
	title = {Center of circle after perspective transformation},
	author = {Xi Wang and Albert Chern and Marc Alexa},
	url = {https://arxiv.org/abs/1902.04541},
	year = {2019},
	date = {2019-02-12},
	organization = {arXiv preprint arXiv:1902.04541 },
	abstract = {Video-based glint-free eye tracking commonly estimates gaze direction based on the pupil center. The boundary of the pupil is fitted with an ellipse and the euclidean center of the ellipse in the image is taken as the center of the pupil. However, the center of the pupil is generally not mapped to the center of the ellipse by the projective camera transformation. This error resulting from using a point that is not the true center of the pupil directly affects eye tracking accuracy. We investigate the underlying geometric problem of determining the center of a circular object based on its projective image. The main idea is to exploit two concentric circles -- in the application scenario these are the pupil and the iris. We show that it is possible to computed the center and the ratio of the radii from the mapped concentric circles with a direct method that is fast and robust in practice. We evaluate our method on synthetically generated data and find that it improves systematically over using the center of the fitted ellipse. Apart from applications of eye tracking we estimate that our approach will be useful in other tracking applications.},
	keywords = {eye tracking},
	pubstate = {published},
	tppubtype = {online}
}

@article{Gaze3D,
	title = {Tracking the Gaze on Objects in 3D: How do People Really Look at the Bunny?},
	author = {Xi Wang and Sebastian Koch and Kenneth Holmqvist and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/xiwang/project_saliency/3D_dataset.html, Project page
https://dl.acm.org/authorize?N688247, ACM Authorized Paper},
	doi = {10.1145/3272127.3275094},
	year = {2018},
	date = {2018-12-03},
	booktitle = {ACM Transaction on Graphics (Proc. of Siggraph Asia)},
	journal = {ACM Transactions on Graphics},
	volume = {37},
	number = {6},
	publisher = {ACM},
	abstract = {We provide the first large dataset of human fixations on physical 3D objects presented in varying viewing conditions and made of different materials. Our experimental setup is carefully designed to allow for accurate calibration and measurement. We estimate a mapping from the pair of pupil positions to 3D coordinates in space and register the presented shape with the eye tracking setup. By modeling the fixated positions on 3D shapes as a probability distribution, we analysis the similarities among different conditions. The resulting data indicates that salient features depend on the viewing direction. Stable features across different viewing directions seem to be connected to semantically meaningful parts. We also show that it is possible to estimate the gaze density maps from view dependent data. The dataset provides the necessary ground truth data for computational models of human perception in 3D.},
	keywords = {eye tracking, Visual Saliency},
	pubstate = {published},
	tppubtype = {article}
}

@article{Herholz:2018,
	title = {Factor Once: Reusing Cholesky  Factorizations on Sub-Meshes},
	author = {Philipp Herholz and Marc Alexa},
	url = {https://dl.acm.org/authorize?N688248, ACM Authorized Paper},
	doi = {10.1145/3272127.3275107},
	year = {2018},
	date = {2018-12-01},
	booktitle = {ACM Transaction on Graphics (Proc. of Siggraph Asia)},
	journal = {ACM Transaction on Graphics},
	volume = {37},
	number = {6},
	publisher = {ACM},
	abstract = {A common operation in geometry processing is solving symmetric and positive semi-definite systems on a subset of a mesh with conditions for the vertices at the boundary of the region. This is commonly done by setting up the linear system for the sub-mesh, factorizing the system (potentially applying preordering to improve sparseness of the factors), and then solving by back-substitution. This approach suffers from a comparably high setup cost for each local operation. We propose to reuse factorizations defined on the full mesh to solve linear problems on sub-meshes. We show how an update on sparse matrices can be performed in a particularly efficient way to obtain the factorization of the operator on a sun-mesh significantly outperforming general factor updates and complete refactorization. We analyze the resulting speedup for a variety of situations and demonstrate that our method outperforms factorization of a new matrix by a factor of up to 10 while never being slower in our experiments.},
	keywords = {geometry processing, linear solvers},
	pubstate = {published},
	tppubtype = {article}
}

@misc{Eyetrackingb,
	title = {Maps of Visual Importance: What is recalled from visual episodic memory?},
	author = {Xi Wang and Kenneth Holmqvist and Marc Alexa},
	year = {2018},
	date = {2018-08-26},
	abstract = {It has been shown that not all fixated locations in a scene are encoded in visual memory. We propose a new way to probe experimentally whether the scene content corresponding to a fixation was considered important by the observer. Our protocol is based on findings from mental imagery showing that fixation locations are reenacted during recall. We track observers' eye movements during stimulus presentation and subsequently, observers are asked to recall the visual content while looking at a neutral background. The tracked gaze locations from the two conditions are aligned using an novel elastic matching algorithm. Motivated by the hypothesis that visual content is recalled only if it has been encoded, we filter fixations from the presentation phase based on fixation locations from recall. The resulting density maps encode fixated scene elements that observers remembered, indicating importance of scene elements. We find that these maps contain top­down rather than bottom­-up features.},
	howpublished = {Presented at 41st European Conference on Visual Perception (ECVP)},
	keywords = {eye tracking},
	pubstate = {published},
	tppubtype = {misc}
}

@article{Piovarci:2018:DAD,
	title = {Design and analysis of directional front projection screens},
	author = {Michal Piovarci and Michael Wessely and Michal Jagielski and Marc Alexa and Wojciech Matusik and Piotr Didyk},
	doi = {https://doi.org/10.1016/j.cag.2018.05.010},
	issn = {0097-8493},
	year = {2018},
	date = {2018-08-01},
	journal = {Computers & Graphics},
	volume = {74},
	pages = {213-224},
	keywords = {computer graphics, fabrication},
	pubstate = {published},
	tppubtype = {article}
}

@online{Visualimportance,
	title = {Maps of Visual Importance},
	author = {Xi Wang and Marc Alexa},
	url = {https://arxiv.org/abs/1712.02142},
	year = {2017},
	date = {2017-12-06},
	organization = {arXiv preprint arXiv:1712.02142},
	abstract = {The importance of an element in a visual stimulus is commonly associated with the fixations during a free-viewing task. We argue that fixations are not always correlated with attention or awareness of visual objects. We suggest to filter the fixations recorded during exploration of the image based on the fixations recorded during recalling the image against a neutral background. This idea exploits that eye movements are a spatial index into the memory of a visual stimulus. We perform an experiment in which we record the eye movements of 30 observers during the presentation and recollection of 100 images. The locations of fixations during recall are only qualitatively related to the fixations during exploration. We develop a deformation mapping technique to align the fixations from recall with the fixation during exploration. This allows filtering the fixations based on proximity and a threshold on proximity provides a convenient slider to control the amount of filtering. Analyzing the spatial histograms resulting from the filtering procedure as well as the set of removed fixations shows that certain types of scene elements, which could be considered irrelevant, are removed. In this sense, they provide a measure of importance of visual elements for human observers.},
	keywords = {eye tracking, mental imagery, Visual Saliency},
	pubstate = {published},
	tppubtype = {online}
}

@article{Herholz:2017,
	title = {Localized solutions of sparse linear systems for geometry processing},
	author = {Philipp Herholz and Timothy A. Davis and Marc Alexa},
	url = {https://dl.acm.org/authorize?N668657, ACM Authorized Paper},
	doi = {10.1145/3130800.3130849},
	year = {2017},
	date = {2017-11-06},
	booktitle = {ACM Transactions on Graphics (TOG) },
	journal = {ACM Transactions on Graphics},
	volume = {36},
	number = {6},
	publisher = {ACM},
	abstract = {Computing solutions to linear systems is a fundamental building block of many geometry processing algorithms. In many cases the Cholesky factorization of the system matrix is computed to subsequently solve the system, possibly for many right-hand sides, using forward and back substitution. We demonstrate how to exploit sparsity in both the right-hand side and the set of desired solution values to obtain significant speedups. The method is easy to implement and potentially useful in any scenarios where linear problems have to be solved locally. We show that this technique is useful for geometry processing operations, in particular we consider the solution of diffusion problems. All problems profit significantly from sparse computations in terms of runtime, which we demonstrate by providing timings for a set of numerical experiments.},
	keywords = {geometry processing, linear solvers},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Fender2017,
	title = {HeatSpace: Automatic Placement of Displays by Empirical Analysis of User Behavior},
	author = {Andreas Fender and David Lindlbauer and Philipp Herholz and Marc Alexa and Jörg Müller},
	url = {http://dl.acm.org/authorize?N40687, Paper
https://www.youtube.com/watch?v=9IQFY_fNz_w, Preview video
https://www.youtube.com/watch?v=pSZHUseWtj4, Video},
	doi = {10.1145/3126594.3126621},
	isbn = {978-1-4503-4981-9},
	year = {2017},
	date = {2017-10-25},
	booktitle = {ACM Symposium on User Interface Software and Technology, UIST'17},
	pages = {611-621 },
	publisher = {ACM},
	series = {UIST'17},
	abstract = {We present HeatSpace, a system that records and empirically analyzes user behavior in a space and automatically suggests positions and sizes for new displays. The system uses depth cameras to capture 3D geometry and users' perspectives over time. To derive possible display placements, it calculates volumetric heatmaps describing geometric persistence and planarity of structures inside the space. It evaluates visibility of display poses by calculating a volumetric heatmap describing occlusions, position within users' field of view, and viewing angle. Optimal display size is calculated through a heatmap of average viewing distance. Based on the heatmaps and user constraints we sample the space of valid display placements and jointly optimize their positions. This can be useful when installing displays in multi-display environments such as meeting rooms, offices, and train stations.},
	keywords = {display placement, HCI},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@misc{Eyetracking,
	title = {3D Eye Tracking in Monocular and Binocular Conditions},
	author = {Xi Wang and Marianne Maertens and Marc Alexa},
	url = {https://social.hse.ru/data/2017/10/26/1157724079/ECEM_Booklet.pdf},
	year = {2017},
	date = {2017-08-20},
	abstract = {Results of eye tracking experiments on vergence are contradictory: for example, the point of vergence has been found in front of as well as behind the target location. The point of vergence is computed by intersecting two lines associated to pupil positions. This approach requires that a fixed eye position corresponds to a straight line of targets in space. However, as long as the targets in an experiment are distributed on a surface (e.g. a monitor), the straight-line assumption cannot be validated; inconsistencies would be hidden in the model estimated during calibration procedure. We have developed an experimental setup for 3D eye tracking based on fiducial markers, whose positions are estimated using computer vision techniques. This allows us to map points in 3D space to pupil positions and, thus, test the straight-line hypothesis. In the experiment, we test both monocular and binocular viewing conditions. Preliminary results suggest that a) the monocular condition is consistent with the straight-line hypothesis and b) binocular viewing shows disparity under the monocular straight line model. This implies that binocular calibration is unsuitable for experiments about vergence. Further analysis is developing a consistent model of binocular viewing.},
	howpublished = {Presented at 19th European Conference on Eye Morvements (ECEM)},
	keywords = {eye tracking},
	pubstate = {published},
	tppubtype = {misc}
}

@inproceedings{Piovarci:2017:DS,
	title = {Directional Screens},
	author = {Michal Piovarci and Michael Wessely and Michal Jagielski and Marc Alexa and Wojciech Matusik and Piotr Didyk},
	url = {https://dl.acm.org/authorize?N655725, Paper (ACM Authorized)},
	doi = {10.1145/3083157.3083162},
	isbn = {978-1-4503-4999-4},
	year = {2017},
	date = {2017-06-12},
	booktitle = {Proceedings of the 1st Annual ACM Symposium on Computational Fabrication},
	pages = {1:1--1:10},
	publisher = {ACM},
	address = {New York, NY, USA},
	abstract = {The goal of display and screen manufacturers is to design devices or surfaces that maximize the perceived image quality, e.g., resolution, brightness, and color reproduction. Very often, a particular viewer location is not taken into account, and the quality is maximized across all viewing directions. This, however, has significant implications for energy efficiency. There is usually a very wide range of viewing directions (e.g., ceiling, floor, or walls) for which the displayed content does not need to be provided. Ignoring this fact results in energy waste due to a significant amount of light reflected towards these regions. In our work, we propose a new type of screen - directional screens, which can be customized depending on a specific audience layout. They can provide up to 5 times increased gain when compared to high-gain screens and up to 15 times brighter reflection than a matte screen. In addition, they provide uniform brightness across all viewing directions, which addresses the problem of "hot-spotting" in high-gain screens. The key idea of our approach is to build a front-projection screen from tiny, highly reflective surfaces. Each of these surfaces is carefully designed so that it reflects the light only towards the audience. In this paper, we propose a complete process for designing and manufacturing such screens. We also validate our concept in simulations and by fabricating several fragments of big screens.},
	keywords = {Digital manufacturing, geometry processing},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Lindlbauer2017,
	title = {Changing the Appearance of Real-World Objects by Modifying Their Surroundings},
	author = {David Lindlbauer and Jörg Müller and Marc Alexa},
	url = {http://dl.acm.org/authorize?N37918, Paper
https://www.cg.tu-berlin.de/research/projects/illusionary-interfaces, Project website
https://www.youtube.com/watch?v=bxWZP_m3PQQ, Preview video
https://www.youtube.com/watch?v=C-XO06wwQuY, Video
},
	doi = {10.1145/3025453.3025795},
	isbn = {978-1-4503-4655-9/17/05},
	year = {2017},
	date = {2017-05-08},
	booktitle = {ACM CHI Conference on Human Factors in Computing Systems, CHI'17},
	pages = {3954-3965},
	publisher = {ACM},
	series = {CHI'17},
	abstract = {We present an approach to alter the perceived appearance of physical objects by controlling their surrounding space. Many real-world objects cannot easily be equipped with displays or actuators in order to change their shape. While common approaches such as projection mapping enable changing the appearance of objects without modifying them, certain surface properties (e.g. highly reflective or transparent surfaces) can make employing these techniques difficult. In this work, we present a conceptual design exploration on how the appearance of an object can be changed by solely altering the space around it, rather than the object itself. In a proof-of-concept implementation, we place objects onto a tabletop display and track them together with users to display perspective-corrected 3D graphics for augmentation. This enables controlling properties such as the perceived size, color, or shape of objects. We characterize the design space of our approach and demonstrate potential applications. For example, we change the contour of a wallet to notify users when their bank account is debited. We envision our approach to gain in importance with increasing ubiquity of display surfaces.},
	keywords = {augmented reality, dynamic appearance, HCI},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Herholz:2015:DDb,
	title = {Diffusion Diagrams: Voronoi Cells and Centroids from Diffusion},
	author = {Philipp Herholz and Felix Haase and Marc Alexa},
	url = {https://cybertron.cg.tu-berlin.de/~philipp/EG2017/},
	year = {2017},
	date = {2017-04-24},
	journal = {Computer Graphics Forum (Proc. of Eurographics)},
	keywords = {computer graphics geometry},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2017:ODS,
	title = {Optimal Discrete Slicing},
	author = {Marc Alexa and Kristian Hildebrand and Sylvain Lefebvre},
	url = {https://dl.acm.org/authorize?N655714, ACM Authorized Paper
},
	doi = {10.1145/2999536},
	issn = {0730-0301},
	year = {2017},
	date = {2017-01-30},
	journal = {ACM Transactions on Graphics},
	volume = {36},
	number = {1},
	pages = {12:1-12:16},
	abstract = {Slicing is the procedure necessary to prepare a shape for layered manufacturing. There are degrees of freedom in this process, such as the starting point of the slicing sequence and the thickness of each slice. The choice of these parameters influences the manufacturing process and its result: The number of slices significantly affects the time needed for manufacturing, while their thickness affects the error. Assuming a discrete setting, we measure the error as the number of voxels that are incorrectly assigned due to slicing. We provide an algorithm that generates, for a given set of available slice heights and a shape, a slicing that is provably optimal. By optimal, we mean that the algorithm generates sequences with minimal error for any possible number of slices. The algorithm is fast and flexible, that is, it can accommodate a user driven importance modulation of the error function and allows the interactive exploration of the desired quality/time tradeoff. We demonstrate the practical importance of our optimization on several three-dimensional-printed results.},
	keywords = {computer graphics, Digital manufacturing, geometry processing, shape approximation},
	pubstate = {published},
	tppubtype = {article}
}

@inbook{Wang2017,
	title = {Accuracy of Monocular Gaze Tracking on 3D Geometry},
	author = {Xi Wang and David Lindlbauer and Christian Lessig and Marc Alexa},
	editor = {Michael Burch and Lewis Chuang and Brian Fisher and Albrecht Schmidt and Daniel Weiskopf},
	url = {http://www.springer.com/de/book/9783319470238},
	isbn = {978-3-319-47023-8},
	year = {2017},
	date = {2017-01-29},
	booktitle = {Eye Tracking and Visualization},
	publisher = {Springer},
	chapter = {10},
	abstract = {Many applications such as data visualization or object recognition benefit from accurate knowledge of where a person is looking at. We present a system for accurately tracking gaze positions on a three dimensional object using a monocular head mounted eye tracker. We accomplish this by (1) using digital manufacturing to create stimuli whose geometry is know to high accuracy, (2) embedding fiducial markers into the manufactured objects to reliably estimate the rigid transformation of the object, and, (3) using a perspective model to relate pupil positions to 3D locations. This combination enables the efficient and accurate computation of gaze position on an object from measured pupil positions. We validate the of our system experimentally, achieving an angular resolution of 0.8 degree and a 1.5 % depth error using a simple calibration procedure with 11 points.},
	keywords = {eye tracking},
	pubstate = {published},
	tppubtype = {inbook}
}

@inproceedings{Lindlbauer2016c,
	title = {Changing the Appearance of Physical Interfaces Through Controlled Transparency},
	author = {David Lindlbauer and Jörg Müller and Marc Alexa},
	url = {http://dl.acm.org/authorize?N25034, Paper
https://www.cg.tu-berlin.de/research/projects/transparency-controlled-physical-interfaces/, Project website
https://www.youtube.com/watch?time_continue=1&v=VrLAoP4wm9o, Preview video
https://www.youtube.com/watch?v=f3e3SI-CKBM, Video},
	doi = {10.1145/2984511.2984556},
	isbn = {978-1-4503-4189-9},
	year = {2016},
	date = {2016-10-18},
	booktitle = {29th Annual Symposium on User Interface Software and Technology, UIST'16},
	pages = {425-435},
	publisher = {ACM},
	series = {UIST'16},
	abstract = {We present physical interfaces that change their appearance through controlled transparency. These transparency-controlled physical interfaces are well suited for applications where communication through optical appearance is sufficient, such as ambient display scenarios. They transition between perceived shapes within milliseconds, require no mechanically moving parts and consume little energy. We build 3D physical interfaces with individually controllable parts by laser cutting and folding a single sheet of transparency-controlled material. Electrical connections are engraved in the surface, eliminating the need for wiring individual parts. We consider our work as complementary to current shape-changing interfaces. While our proposed interfaces do not exhibit dynamic tangible qualities, they have unique benefits such as the ability to create apparent holes or nesting of objects. We explore the benefits of transparency-controlled physical interfaces by characterizing their design space and showcase four physical prototypes: two activity indicators, a playful avatar, and a lamp shade with dynamic appearance.},
	keywords = {dynamic appearance, HCI, transparency control},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Wang2016,
	title = {Measuring Visual Salience of 3D Printed Objects},
	author = {Xi Wang and David Lindlbauer and Christian Lessig and Marianne Maertens and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/xiwang/project_saliency/index.html, Project page
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7478427&newsearch=true&queryText=Measuring%20Visual%20Salience%20of%203D%20Printed%20Objects, PDF
http://cybertron.cg.tu-berlin.de/xiwang/visual_salience_video.mp4, Video},
	doi = {10.1109/MCG.2016.47},
	issn = {0272-1716},
	year = {2016},
	date = {2016-05-25},
	journal = {IEEE Computer Graphics and Applications Special Issue on Quality Assessment and Perception in Computer Graphics },
	abstract = {We investigate human viewing behavior on physical realizations of 3D objects. Using an eye tracker with scene camera and fiducial markers we are able to gather fixations on the surface of the presented stimuli. This data is used to validate assumptions regarding visual saliency so far only experimentally analyzed using flat stimuli. We provide a way to compare fixation sequences from different subjects as well as a model for generating test sequences of fixations unrelated to the stimuli. This way we can show that human observers agree in their fixations for the same object under similar viewing conditions – as expected based on similar results for flat stimuli. We also develop a simple procedure to validate computational models for visual saliency of 3D objects and use it to show that popular models of mesh salience based on the center surround patterns fail to predict fixations.},
	keywords = {3D Printing, eye tracking, Mesh Saliency, Visual Saliency},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Lindlbauer2016b,
	title = {Combining Shape-Changing Interfaces and Spatial Augmented Reality Enables Extended Object Appearance },
	author = {David Lindlbauer and Jens Emil Grønbæk and Mortensen Birk and Kim Halskov and Marc Alexa and Jörg Müller},
	url = {http://dl.acm.org/authorize?N04344, Paper
http://www.cg.tu-berlin.de/research/projects/sci-and-ar/, Project page
https://www.youtube.com/watch?v=uyvBJqv3s_M, Preview video
https://www.youtube.com/watch?v=fWREdKL2Kus, Video},
	doi = {10.1145/2858036.2858457},
	isbn = {978-1-4503-3362-7},
	year = {2016},
	date = {2016-05-07},
	booktitle = {SIGCHI Conference on Human Factors in Computing Systems, CHI'16},
	pages = {791-802},
	publisher = {ACM},
	series = {CHI'16},
	abstract = {We propose combining shape-changing interfaces and spatial augmented reality for extending the space of appearances and interactions of actuated interfaces. While shape-changing interfaces can dynamically alter the physical appearance of objects, the integration of spatial augmented reality additionally allows for dynamically changing objects' optical appearance with high detail. This way, devices can render currently challenging features such as high frequency texture or fast motion. We frame this combination in the context of computer graphics with analogies to established techniques for increasing the realism of 3D objects such as bump mapping. This extensible framework helps us identify challenges of the two techniques and benefits of their combination. We utilize our prototype shape-changing device enriched with spatial augmented reality through projection mapping to demonstrate the concept. We present a novel mechanical distance-fields algorithm for real-time fitting of mechanically constrained shape-changing devices to arbitrary 3D graphics. Furthermore, we present a technique for increasing effective screen real estate for spatial augmented reality through view-dependent shape change. },
	keywords = {augmented reality, HCI, shape-changing interfaces},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Richter:2016:CM3,
	title = {Constrained Modeling of 3-valent Meshes Using a Hyperbolic Deformation Metric},
	author = {Ronald Richter and Jan Eric Kyprianidis and Boris Springborn and Marc Alexa},
	doi = {10.1111/cgf.12805},
	year = {2016},
	date = {2016-01-28},
	journal = {Computer Graphics Forum},
	abstract = {Polygon meshes with 3-valent vertices often occur as the frame of free-form surfaces in architecture, in which rigid beams are connected in rigid joints. 
For modeling such meshes it is desirable to measure the deformation of the joints' shapes. We show that it is natural to represent joint shapes as points in hyperbolic 3-space. This endows the space of joint shapes with a geometric structure that facilitates computation. We use this structure to optimize meshes towards different constraints, and we believe that it will be useful for other applications as well.},
	note = {in press},
	keywords = {computer graphics, Digital manufacturing, geometry processing, shape approximation},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Tompkin:2015:J5D,
	title = {Joint 5D Pen Input for Light Field Displays},
	author = {James Tompkin and Samuel Muff and James McCann and Hanspeter Pfister and Jan Kautz and Marc Alexa and Wojciech Matusik},
	url = {http://jamestompkin.com/pubs/lightfieldpainting/index.html, Project Website},
	doi = {10.1145/2807442.2807477},
	isbn = {978-1-4503-3779-3},
	year = {2015},
	date = {2015-11-10},
	booktitle = {The 28th Annual ACM Symposium on User Interface Software and Technology, UIST'15},
	pages = {637--647},
	publisher = {ACM},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@incollection{Wang2015,
	title = {Accuracy of Monocular Gaze Tracking on 3D Geometry},
	author = {Xi Wang and David Lindlbauer and Christian Lessig and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/xiwang/project_saliency/index.html, Project page
http://www.vis.uni-stuttgart.de/etvis/ETVIS_2015.html, PDF},
	year = {2015},
	date = {2015-10-25},
	booktitle = {Workshop on Eye Tracking and Visualization (ETVIS) co-located with IEEE VIS},
	abstract = {Many applications in visualization benefit from accurate knowledge of where a person is looking at. We present a system for accurately tracking gaze positions on a three dimensional object using a monocular head mounted eye tracker. We accomplish this by 1) using digital manufacturing to create stimuli with accurately known geometry, 2) embedding fiducial markers directly into the manufactured objects to reliably estimate the rigid transformation of the object, and, 3) using a perspective model to relate pupil positions to 3D locations. This combination enables the efficient and accurate computation of gaze position on an object from measured pupil positions. We validate the accuracy of our system experimentally, achieving an angular resolution of 0.8◦ and a 1.5%
depth error using a simple calibration procedure with 11 points.},
	keywords = {accuracy, calibration, eye tracking},
	pubstate = {published},
	tppubtype = {incollection}
}

@article{Richter:2015:BM,
	title = {Beam Meshes},
	author = {Ronald Richter and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/ronald/files/beams.pdf},
	doi = {doi:10.1016/j.cag.2015.08.007},
	year = {2015},
	date = {2015-10-15},
	journal = {Computers & Graphics},
	abstract = {We present an approach for representing free-form geometry with a set of beams with rectangular cross-section. This requires the edges of the mesh to be free of torsion. We generate such meshes in a two step procedure: first we generate a coarse, low valence mesh approximation using a new variant of anisotropic centroidal Voronoi tessellation. Then we modify the mesh and create beams by incorporating constraints using iterative optimization. For fabrication we provide solutions for designing the joints, generating a cutting place for CNC machines, and suggesting a building sequence. The approach is demonstrated at several virtual and real results.},
	keywords = {centroidal voronoi diagram, Digital manufacturing, geometry processing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Herholz:2015:PLP,
	title = {Perfect Laplacians for Polygon Meshes},
	author = {Philipp Herholz and Jan Eric Kyprianidis and Marc Alexa},
	editor = {Mirela Ben-Chen and Ligang Liu},
	url = {http://cybertron.cg.tu-berlin.de/~philipp/SGP2015/, Project Website},
	doi = {10.1111/cgf.12709},
	year = {2015},
	date = {2015-07-06},
	journal = {Computer Graphics Forum (SGP 2015)},
	abstract = {A discrete Laplace-Beltrami operator is called perfect if it possesses all the important properties of its smooth counterpart. It is known which triangle meshes admit perfect Laplace operators and how to fix any other mesh by changing the combinatorics. We extend the characterization of meshes that admit perfect Laplacians to general polygon meshes. More importantly, we provide an algorithm that computes a perfect Laplace operator for any polygon mesh without changing the combinatorics, although, possibly changing the embedding. We evaluate this algorithm and demonstrate it at applications.},
	keywords = {computer graphics, geometry processing, laplacian, polygonal meshes},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Lang2015,
	title = {The Markov Pen: Online Synthesis of Free-Hand Drawing Styles},
	author = {Katrin Lang and Marc Alexa},
	editor = {David Mould and Pierre Bénard},
	url = {http://cybertron.cg.tu-berlin.de/klang/markov-pen/, Project Website
},
	doi = {10.2312/exp.20151193},
	year = {2015},
	date = {2015-06-20},
	booktitle = {International Symposium on Non-Photorealistic Animation and Rendering (NPAR) 2015},
	publisher = {The Eurographics Association},
	abstract = {Learning expressive curve styles from example is crucial for interactive or computer-based narrative illustrations. We propose a method for online synthesis of free-hand drawing styles along arbitrary base paths by means of an autoregressive Markov Model. Choice on further curve progression is made while drawing, by sampling from a series of previously learned feature distributions subject to local curvature. The algorithm requires no user adjustable parameters other than one short example style. It may be used as a custom “random brush” designer in any task that requires rapid placement of a large number of detail-rich shapes that are tedious to create manually.},
	keywords = {markov pen, non-photorealistic rendering, sketching},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Herholz:2015:AGH,
	title = {Approximating Free-form Geometry with Height Fields for Manufacturing},
	author = {Philipp Herholz and Wojciech Matusik and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/~philipp/EG2015/ , Project Website
http://cybertron.cg.tu-berlin.de/~philipp/EG2015/files/HerholzEG2015.pdf, Full Paper
https://youtu.be/sqSkZzOtiI0, Movie},
	year = {2015},
	date = {2015-05-01},
	journal = {Computer Graphics Forum (Eurographics 2015)},
	volume = {34},
	number = {2},
	pages = {239-251},
	abstract = {We consider the problem of manufacturing free-form geometry with classical manufacturing techniques, such as mold casting or 3-axis milling. We determine a set of constraints that are necessary for manufacturability and then decompose and, if necessary, deform the shape to satisfy the constraints per segment. We show that many objects can be generated from a small number of (mold-)pieces if some deformation is acceptable. We provide examples of actual molds and the resulting manufactured objects.},
	keywords = {fabrication, geometry processing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2015:EDM,
	title = {Error diffusion on meshes},
	author = {Marc Alexa and Jan Eric Kyprianidis},
	url = {http://cybertron.cg.tu-berlin.de/p/smi2014/, Project Website},
	doi = {10.1016/j.cag.2014.09.010},
	year = {2015},
	date = {2015-02-01},
	journal = {Computers & Graphics},
	volume = {46},
	pages = {336--344},
	abstract = {We consider the problem of quantization for surface graphs. In particular, we generalize the process of error diffusion to meshes and then compare different paths on the surface when used for error diffusion. We suggest paths for processing mesh elements that lead to better distributions of available neighbors for error diffusion. We demonstrate the potential benefit of error diffusion at several mesh processing applications: quantization of differential mesh coordinates, including an extension to animated geometry, and vertex subset selection for mesh simplification. These applications allow us to compare different paths objectively. We find that the linear time solution results in excellent overall performance, outperforming other traversals taken from the literature. We conclude that the proposed path can be taken as a starting point for any application of error diffusion on meshes.},
	keywords = {animated mesh, compression, dithering, ecimation, error diffusion, geometry processing, quantization},
	pubstate = {published},
	tppubtype = {article}
}

@article{Richter:2015:MCVT,
	title = {Mahalanobis centroidal Voronoi tessellations},
	author = {Ronald Richter and Marc Alexa},
	url = {http://www.sciencedirect.com/science/article/pii/S0097849314000971},
	doi = {doi:10.1016/j.cag.2014.09.009},
	year = {2015},
	date = {2015-02-01},
	journal = {Computers & Graphics},
	volume = {46},
	pages = {48–54},
	abstract = {Anisotropic centroidal Voronoi tessellations (CVT) are a useful tool for segmenting surfaces in geometric modeling. We present a new approach to anisotropic CVT, where the local distance metric is learned from the embedding of the shape. Concretely, we define the distance metric implicitly as the minimizer of the CVT energy. Constraining the metric tensors to have unit determinant leads to the optimal distance metric being the inverse covariance matrix of the data (i.e. Mahalanobis distances). We explicitly cover the case of degenerate covariance and provide an algorithm to minimize the CVT energy. The resulting technique has applications in shape approximation, particularly in the case of noisy data, where normals are unreliable. We also put our approach in the context of other techniques. Among others, we show that Variational Shape Approximation can be interpreted in the same framework by constraining the metric tensor based on another norm.},
	keywords = {computer graphics, geometry processing, polygonal meshes, voronoi tessellation},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2015:CAF,
	title = {Computational Aspects of Fabrication},
	author = {Marc Alexa and Bernd Bickel and Sara McMains and Holly E. Rushmeier},
	url = {http://www.dagstuhl.de/en/program/calendar/semhp/?semnr=14361, Dagstuhl Workshop},
	doi = {10.4230/DagRep.4.8.126},
	issn = {2192-5283},
	year = {2015},
	date = {2015-01-01},
	journal = {Dagstuhl Reports},
	volume = {4},
	number = {8},
	pages = {126-150},
	abstract = {As manufacturing goes digital, the current understanding of industrial production will change fundamentally. The digital age in manufacturing is coupled with new output devices that allow rapid customization and rapid manufacturing, revolutionizing the way we design, develop, distribute, fabricate, and consume products. We need to find computational models that support this new way of production thinking and lead its technological understanding. This opens challenges for many areas of science research, such as material science, chemistry, and engineering, but also and perhaps foremost computer sciences. The currently available digital content creation pipelines, algorithms, and tools cannot fully explore new manufacturing capabilities. To meet these demands, we need a deep understanding of computer graphics fundamentals: Shape, appearance of shape and materials, and physically-based simulation and animation. When designing an object, there is an inherent interplay among all these fundamental aspects. The purpose of this seminar is to bring together leading experts from academia and industry in the area of computer graphics, geometry processing, and digital fabrication. The goal is to address fundamental questions and issues related to computational aspects of fabrication and jump-start collaborations that will pioneer new approaches in this area.},
	keywords = {computer graphics, fabrication},
	pubstate = {published},
	tppubtype = {article}
}

@incollection{Herholz2014:FFS,
	title = {Turning free-form surfaces into manufacturable components},
	author = {Philipp Herholz and Marc Alexa and Wojciech Matusik},
	year = {2014},
	date = {2014-06-27},
	booktitle = {ACM SIGGRAPH 2014 Studio},
	keywords = {computer graphics, fabrication, free-form surfaces},
	pubstate = {published},
	tppubtype = {incollection}
}

@article{Bickel:2013:CAF,
	title = {Computational Aspects of Fabrication: Modeling, Design, and 3D Printing},
	author = {Bernd Bickel and Marc Alexa},
	doi = {10.1109/MCG.2013.89},
	issn = {0272-1716},
	year = {2013},
	date = {2013-11-01},
	journal = {IEEE Computer Graphics and Applications},
	volume = {33},
	number = {6},
	pages = {24-25},
	keywords = {Digital manufacturing, fabrication},
	pubstate = {published},
	tppubtype = {article}
}

@article{Limper:2013:POP,
	title = {The POP Buffer: Rapid Progressive Clustering by Geometry Quantization},
	author = {Max Limper and Yvonne Jung and Johannes Behr and Marc Alexa},
	url = {http://diglib.eg.org/EG/DL/CGF/volume32/issue7/v32i7pp197-206.pdf.abstract.pdf;internal&action=action.digitallibrary.ShowPaperAbstract, EG Digital Library
http://x3dom.org/pop/, Project Website},
	year = {2013},
	date = {2013-10-08},
	journal = {Computer Graphics Forum},
	volume = {32},
	number = {7},
	pages = {197-206},
	abstract = {Within this paper, we present a novel, straightforward progressive encoding scheme for general triangle soups, which is particularly well-suited for mobile and Web-based environments due to its minimal requirements on the client\'s hardware and software. Our rapid encoding method uses a hierarchy of quantization to effectively reorder the original primitive data into several nested levels of detail. The resulting stateless buffer can progressively be transferred as-is to the GPU, where clustering is efficiently performed in parallel during rendering. We combine our approach with a crack-free mesh partitioning scheme to obtain a straightforward method for fast streaming and basic view-dependent LOD control.},
	keywords = {computer graphics, interactive, polygonal meshes, shape approximation},
	pubstate = {published},
	tppubtype = {article}
}

@article{Hildebrand2013b,
	title = {Sketch-Based Pipeline for Mass Customization},
	author = {Kristian Hildebrand and Marc Alexa},
	year = {2013},
	date = {2013-09-27},
	journal = {Design Modelling Symposium},
	keywords = {computer graphics, Digital manufacturing, shape retrieval, sketch-based image retrieval, sketching},
	pubstate = {published},
	tppubtype = {article}
}

@article{Rouiller2013,
	title = {3D Printing Spatially Varying BRDFs},
	author = {Olivier Rouiller and Bernd Bickel and Wojciech Matusik and Marc Alexa and Jan Kautz},
	url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6606796&tag=1, IEEE Xplore},
	issn = {0272-1716},
	year = {2013},
	date = {2013-09-27},
	journal = {IEEE Computer Graphics and Applications},
	volume = {33},
	number = {6},
	pages = {48-57},
	keywords = {computer graphics, Digital manufacturing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Snelgrove:2013:PWL,
	title = {Parallax Walls: Light fields from occlusion on height fields},
	author = {Xavier Snelgrove and Thiago Pereira and Wojciech Matusik and Marc Alexa},
	url = {http://dx.doi.org/10.1016/j.cag.2013.07.002, DOI},
	issn = {0097-8493},
	year = {2013},
	date = {2013-09-02},
	journal = {Computers & Graphics},
	volume = {37},
	number = {8},
	pages = {974-982},
	keywords = {computer graphics, Digital manufacturing, fabrication},
	pubstate = {published},
	tppubtype = {article}
}

@article{Hildebrand2013,
	title = {Orthogonal slicing for additive manufacturing},
	author = {Kristian Hildebrand and Bernd Bickel and Marc Alexa},
	url = {http://www.sciencedirect.com/science/article/pii/S009784931300085X, Publication},
	issn = {0097-8493},
	year = {2013},
	date = {2013-07-12},
	journal = {Computers & Graphics},
	keywords = {Digital manufacturing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Gerstner2013,
	title = {Pixelated image abstraction with integrated user constraints},
	author = {Timothy Gerstner and Doug DeCarlo and Marc Alexa and Adam Finkelstein and Yotam Gingold and Andrew Nealen},
	url = {http://dx.doi.org/10.1016/j.cag.2012.12.007, DOI},
	issn = {0097-8493},
	year = {2013},
	date = {2013-05-05},
	journal = {Computers & Graphics},
	volume = {37},
	number = {5},
	pages = {333-347},
	keywords = {computer graphics, image synthesis},
	pubstate = {published},
	tppubtype = {article}
}

@article{Eitz2012,
	title = {Sketch-Based Shape Retrieval},
	author = {Mathias Eitz and Ronald Richter and Kristian Hildebrand and Tamy Boubekeur and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/eitz/projects/sbsr, Project Page
http://dl.acm.org/citation.cfm?id=2185527, ACM DL
http://cybertron.cg.tu-berlin.de/kristian/movies/sig12_sbsr.mp4, Movie 
http://cybertron.cg.tu-berlin.de/eitz/slides/sig12_sbsr.pptx, Slides 
http://scholar.google.de/citations?view_op=view_citation&hl=en&user=KNwXLLsAAAAJ&sortby=pubdate&citation_for_view=KNwXLLsAAAAJ:WbkHhVStYXYC, Google Scholar},
	year = {2012},
	date = {2012-08-02},
	journal = {ACM Transactions on Graphics, Proceedings SIGGRAPH (to appear)},
	volume = {31},
	number = {4},
	abstract = {We develop a system for 3D object retrieval based on sketched feature lines as input. For objective evaluation, we collect a large number of query sketches from human users that are related to an existing data base of objects. The sketches turn out to be generally quite abstract with large local and global deviations from the original shape. Based on this observation, we decide to use a bag-of-features approach over computer generated line drawings of the objects. We develop a targeted feature transform based on Gabor filters for this system. We can show objectively that this transform is better suited than other approaches from the literature developed for similar tasks. Moreover, we demonstrate how to optimize the parameters of our, as well as other approaches, based on the gathered sketches. In the resulting comparison, our approach is significantly better than any other system described so far.},
	keywords = {bag-of-features, lo-, shape retrieval, visual search},
	pubstate = {published},
	tppubtype = {article}
}

@incollection{Tompkin:2012:ILF,
	title = {Interactive light field painting},
	author = {James Tompkin and Samuel Muff and Stansilav Jakuschevskij and Jim McCann and Jan Kautz and Marc Alexa and Wojciech Matusik},
	url = {http://dl.acm.org/citation.cfm?doid=2343456.2343468, DOI},
	isbn = {978-1-4503-1680-4},
	year = {2012},
	date = {2012-08-01},
	booktitle = {ACM SIGGRAPH 2012 Emerging Technologies},
	number = {12},
	keywords = {computer graphics, interactive, sketching},
	pubstate = {published},
	tppubtype = {incollection}
}

@inproceedings{Gerstner:2012:PIA:2330147.2330154,
	title = {Pixelated image abstraction},
	author = {Timothy Gerstner and Doug DeCarlo and Marc Alexa and Adam Finkelstein and Yotam Gingold and Andrew Nealen},
	url = {http://dl.acm.org/citation.cfm?id=2330147.2330154, ACM DL},
	isbn = {978-3-905673-90-6},
	year = {2012},
	date = {2012-05-09},
	booktitle = {Proceedings of the Symposium on Non-Photorealistic Animation and Rendering},
	pages = {29--36},
	publisher = {Eurographics Association},
	address = {Aire-la-Ville, Switzerland, Switzerland},
	series = {NPAR '12},
	abstract = {We present an automatic method that can be used to abstract high resolution images into very low resolution outputs with reduced color palettes in the style of pixel art. Our method simultaneously solves for a mapping of features and a reduced palette needed to construct the output image. The results are an approximation to the results generated by pixel artists. We compare our method against the results of a naive process common to image manipulation programs, as well as the hand-crafted work of pixel artists. Through a formal user study and interviews with expert pixel artists we show that our results offer an improvement over the naive methods.},
	keywords = {computer graphics, image synthesis},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Bermano:2012:SHP:2322116.2322129,
	title = {ShadowPix: Multiple Images from Self Shadowing},
	author = {Amit Bermano and Ilya Baran and Marc Alexa and Wojciech Matusk},
	url = {http://dx.doi.org/10.1111/j.1467-8659.2012.03038.x, Publisher},
	issn = {0167-7055},
	year = {2012},
	date = {2012-05-01},
	journal = {Computer Graphics Forum},
	volume = {31},
	number = {2pt3},
	pages = {593--602},
	publisher = {John Wiley & Sons, Inc.},
	address = {New York, NY, USA},
	keywords = {computer graphics, fabrication},
	pubstate = {published},
	tppubtype = {article}
}

@article{eitz2012hdhso,
	title = {How Do Humans Sketch Objects?},
	author = {Mathias Eitz and James Hays and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/eitz/projects/classifysketch, Project Page
http://dl.acm.org/authorize?6726876, ACM DL
http://cybertron.cg.tu-berlin.de/eitz/movies/sig12_classifysketch.mp4, Movie
http://cybertron.cg.tu-berlin.de/eitz/slides/sig12_classification.pptx, Slides
http://itunes.apple.com/app/whatsmysketch/id542242001, iOS Application},
	year = {2012},
	date = {2012-01-01},
	journal = {ACM Transactions on Graphics (Proceedings SIGGRAPH)},
	volume = {31},
	number = {4},
	pages = {44:1--44:10},
	abstract = {Humans have used sketching to depict our visual world since prehistoric times. Even today, sketching is possibly the only rendering technique readily available to all humans. This paper is the first large scale exploration of human sketches. We analyze the distribution of non-expert sketches of everyday objects such as ‘teapot’ or ‘car’. We ask humans to sketch objects of a given category and gather 20,000 unique sketches evenly distributed over 250 object categories. With this dataset we perform a perceptual study and find that humans can correctly identify the object category of a sketch 73% of the time. We compare human performance against computational recognition methods. We develop a bag-of-features sketch representation and use multi-class support vector machines, trained on our sketch dataset, to classify sketches. The resulting recognition method is able to identify unknown sketches with 56% accuracy (chance is 0.4%). Based on the computational model, we demonstrate an interactive sketch recognition system. We release the complete crowd-sourced dataset of sketches to the community.},
	keywords = {sketching},
	pubstate = {published},
	tppubtype = {article}
}

@article{Hildebrand2012,
	title = {crdbrd : Shape Fabrication by Sliding Planar Slices},
	author = {Kristian Hildebrand and Bernd Bickel and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/kristian/files/crdbrd.pdf, Full Paper
http://cybertron.cg.tu-berlin.de/kristian/movies/crdbrd.mp4, Movie
http://cybertron.cg.tu-berlin.de/kristian/files/eg2012-crdbrd.ppt, Slides
http://scholar.google.de/citations?view_op=view_citation&hl=en&user=KNwXLLsAAAAJ&sortby=pubdate&citation_for_view=KNwXLLsAAAAJ:tOudhMTPpwUC, Google Scholar},
	year = {2012},
	date = {2012-01-01},
	journal = {Computer Graphics Forum (Eurographics 2012)},
	volume = {31},
	number = {2},
	abstract = {We introduce an algorithm and representation for fabricating 3D shape abstractions using mutually intersecting planar cut-outs. The planes have prefabricated slits at their intersections and are assembled by sliding them together. Based on an analysis of construction rules, we propose an extended binary space partitioning tree as an efficient representation of such cardboard models which allows us to quickly evaluate the feasibility of newly added planar elements. The complexity of insertion order quickly increases with the number of planar elements and manual analysis becomes intractable. We provide tools for generating cardboard sculptures with guaranteed constructibility.},
	keywords = {fabrication, shape approximation, slicing},
	pubstate = {published},
	tppubtype = {article}
}

@article{Eitz2010,
	title = {Sketch-Based Image Retrieval: Benchmark and Bag-of-Features Descriptors},
	author = {Mathias Eitz and Kristian Hildebrand and Tamy Boubekeur and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/eitz/tvcg_benchmark/index.html, Project Webpage http://cybertron.cg.tu-berlin.de/kristian/files/sbir.pdf, Full Paper http://www.ncbi.nlm.nih.gov/pubmed/21173450, PubMed http://cybertron.cg.tu-berlin.de/kristian/movies/sbir.mp4, Movie http://scholar.google.de/citations?view_op=view_citation&hl=en&user=KNwXLLsAAAAJ&cstart=20&sortby=pubdate&citation_for_view=KNwXLLsAAAAJ:TFP_iSt0sucC, Google Scholar},
	year = {2011},
	date = {2011-01-01},
	journal = {IEEE transactions on visualization and computer graphics},
	abstract = {We introduce a benchmark for evaluating the performance of large scale sketch-based image retrieval systems. The necessary data is acquired in a controlled user study where subjects rate how well given sketch/image pairs match. We suggest how to use the data for evaluating the performance of sketch-based image retrieval systems. The benchmark data as well as the large image database are made publicly available for further studies of this type. Furthermore, we develop new descriptors based on the bag-of-features approach and use the benchmark to demonstrate that they significantly outperform other descriptors in the literature.},
	keywords = {image retrieval, sketching},
	pubstate = {published},
	tppubtype = {article}
}

@article{Eitz2011,
	title = {Photosketcher: Interactive Sketch-Based Image Synthesis},
	author = {Mathias Eitz and Ronald Richter and Kristian Hildebrand and Tamy Boubekeur and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/eitz/pdf/2011_cga_photosketcher.pdf, Full Paper http://dx.doi.org/10.1109/MCG.2011.67, DOI http://scholar.google.de/citations?view_op=view_citation&hl=en&user=KNwXLLsAAAAJ&cstart=20&sortby=pubdate&citation_for_view=KNwXLLsAAAAJ:hC7cP41nSMkC, Google Scholar},
	year = {2011},
	date = {2011-01-01},
	journal = {IEEE Computer Graphics and Applications},
	volume = {31},
	number = {6},
	pages = {56--66},
	abstract = {We introduce Photosketcher, an interactive system for progressively synthesizing novel images using only sparse user sketches as the input. Compared to existing approaches for synthesising images from parts of other images, Photosketcher works on the image content exclusively, no keywords or other metadata associated with the images is required. Users sketch the rough shape of a desired image part and we automatically search a large collection of images for images containing that part. The search is based on a bag-of-features approach using local descriptors for translation invariant part retrieval. The compositing step again is based on user scribbles: from the scribbles we predict the desired part using Gaussian Mixture Models and compute an optimal seam using Graphcut. Optionally, Photosketcher lets users blend the composite image in the gradient domain to further reduce visible seams. We demonstrate that the resulting system allows interactive generation of complex images.},
	keywords = {image synthesis, sketching},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Hahne:2011:EFT,
	title = {Exposure Fusion for Time-Of-Flight Imaging},
	author = {Uwe Hahne and Marc Alexa},
	year = {2011},
	date = {2011-01-01},
	booktitle = {Proceedings of Pacific Graphics 2011},
	volume = {30 (2011)},
	number = {7},
	abstract = {This work deals with the problem of automatically choosing the correct exposure (or integration) time for time-of-flight depth image capturing. We apply methods known from high dynamic range imaging to combine depth images taken with differing integration times in order to produce high quality depth maps. We evaluate the quality of these depth maps by comparing the performance in reconstruction of planar textured patches and in the 3D reconstruction of an indoor scene. Our solution is fast enough to capture the images at interactive frame rates and also flexible to deal with any amount of exposures.},
	note = {to appear},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Perkunder:2010:SMI,
	title = {Shape modeling with sketched feature lines in immersive 3D environments},
	author = {Helen Perkunder and Johann Habakuk Israel and Marc Alexa},
	editor = {Marc Alexa and Ellen Yi-Luen Do},
	doi = {10.2312/SBM/SBM10/127-134},
	isbn = {978-3-905674-25-5},
	year = {2010},
	date = {2010-07-01},
	booktitle = {Proceedings of the Seventh Sketch-Based Interfaces and Modeling Symposium},
	pages = {127--134},
	publisher = {Eurographics Association},
	series = {SBIM},
	keywords = {computer graphics, HCI, sketching},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2010:RAI,
	title = {Reliefs as images},
	author = {Marc Alexa and Wojciech Matusik},
	issn = {0730-0301},
	year = {2010},
	date = {2010-01-01},
	journal = {ACM Transactions on Graphics},
	volume = {29},
	number = {4},
	pages = {1–7},
	publisher = {ACM},
	address = {New York, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Buchholz:2010:BSAG,
	title = {Binary Shading Using Geometry and Appearance},
	author = {Bert Buchholz and Tamy Boubekeur and Doug DeCarlo and Marc Alexa},
	year = {2010},
	date = {2010-01-01},
	journal = {Computer Graphics Forum},
	volume = {29},
	number = {6},
	pages = {1981-1992},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Eitz2010a,
	title = {An evaluation of descriptors for large-scale image retrieval from sketched feature lines},
	author = {Mathias Eitz and Kristian Hildebrand and Tamy Boubekeur and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/eitz/pdf/2010_cag.pdf, Full Paper http://dx.doi.org/10.1016%2fj.cag.2010.07.002, DOI http://scholar.google.de/citations?view_op=view_citation&hl=en&user=KNwXLLsAAAAJ&cstart=20&sortby=pubdate&citation_for_view=KNwXLLsAAAAJ:mB3voiENLucC, Google Scholar},
	year = {2010},
	date = {2010-01-01},
	journal = {Computers & Graphics},
	volume = {34},
	pages = {482----498},
	abstract = {We address the problem of fast, large scale sketch-based image retrieval, searching in a database of over one million images. We show that current retrieval methods do not scale well towards large databases in the context of interactively supervised search and propose two different approaches for which we objectively evaluate that they significantly outperform existing approaches. The proposed descriptors are constructed such that both the full color image and the sketch undergo exactly the same preprocessing steps. We first search for an image with similar structure, analyzing gradient orientations. Then, best matching images are clustered based on dominant color distributions, to offset the lack of color-based decision during the initial search. Overall, the query results demonstrate that the system offers intuitive access to large image databases using a user-friendly sketch-and-browse interface.},
	keywords = {image databases, image descriptors, mpeg-7, sketch-based image retrieval},
	pubstate = {published},
	tppubtype = {article}
}

@article{Eitz2010b,
	title = {Sketch-based 3D shape retrieval},
	author = {Mathias Eitz and Kristian Hildebrand and Tamy Boubekeur and Marc Alexa and Telecom Paristech Cnrs},
	url = {http://cybertron.cg.tu-berlin.de/eitz/pdf/2010_sbsr.pdf, Full Paper http://cybertron.cg.tu-berlin.de/eitz/movies/sig10_sbsr.mov, Movie http://cybertron.cg.tu-berlin.de/eitz/slides/sig10_sbsr.pptx, Slides http://dx.doi.org/10.1145/1837026.1837033, DOI http://scholar.google.de/citations?view_op=view_citation&hl=en&user=KNwXLLsAAAAJ&cstart=20&sortby=pubdate&citation_for_view=KNwXLLsAAAAJ:RGFaLdJalmkC, Google Scholar},
	year = {2010},
	date = {2010-01-01},
	journal = {ACM SIGGRAPH 2010 Talks},
	abstract = {As large collections of 3D models are starting to become as common as public image collections, the need arises to quickly locate models in such collections. Models are often insufficiently annotated such that a keyword based search is not promising. Our approach for content based searching of 3D models relies entirely on visual analysis and is based on the observation that a large part of our perception of shapes stems from their salient features, usually captured by dominant lines in their display. Recent research on such feature lines has shown that 1) people mostly draw the same lines when asked to depict a certain model and 2) the shape of an object is well represented by the set of feature lines generated by recent NPR line drawing algorithms. Consequently, we suggest an image based approach for 3D shape retrieval, exploiting the similarity of human sketches and the results of current line drawing algorithms. Our search engine takes a sketch of the desired model drawn by a user as the input and compares this sketch to a set of line drawings automatically generated for each of the models in the collection.},
	keywords = {shape retrieval},
	pubstate = {published},
	tppubtype = {article}
}

@article{Oztireli:2010:RAI,
	title = {Spectral Sampling of Manifolds},
	author = {Cengiz Öztireli and Marc Alexa and Markus Gross},
	url = {http://dl.acm.org/authorize?313592, ACM DL},
	year = {2010},
	date = {2010-01-01},
	journal = {ACM Transactions on Graphics},
	volume = {29},
	number = {5},
	pages = {1–7},
	publisher = {ACM},
	address = {New York, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{richter2010browsing,
	title = {Interactively Browsing Large Image Collections},
	author = {Ronald Richter and Mathias Eitz and Marc Alexa},
	url = {http://cybertron.cg.tu-berlin.de/eitz/pdf/2010_browsing.pdf, Full Paper http://cybertron.cg.tu-berlin.de/eitz/movies/sig10_browsing.mov, Movie http://cybertron.cg.tu-berlin.de/eitz/slides/sig10_browsing.pptx, Slides http://dx.doi.org/10.1145/1837026.1837081, DOI},
	year = {2010},
	date = {2010-01-01},
	booktitle = {SIGGRAPH 2010: Talks},
	abstract = {In this paper, we propose a novel method for interactively browsing large image collections, making the user an integral part of the interactive exploration by repeatedly exploiting the amazing ability of humans to quickly identify relevant images from a large set. The method requires only minimal input effort: users simply point to the image in the current display that seems most attractive to them. The system then assembles a representative set of other images from the collection that are likely in its perceptual vicinity. The resulting browsing approach is -- even for novice users -- extremely simple to use and enables an interactive exploration of the collection as well as target-oriented selection towards a specific mental image model.},
	keywords = {image browsing, interactive},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Winkler:2010:MSG,
	title = {Multi-Scale Geometry Interpolation},
	author = {Tim Winkler and Jens Drieseberg and Marc Alexa and Kai Hormann},
	url = {http://www.youtube.com/watch?v=gDPyiDmkcQ4, Video on YouTube},
	year = {2010},
	date = {2010-01-01},
	journal = {Computer Graphics Forum},
	volume = {29},
	number = {2},
	pages = {309-318},
	note = {Proceedings of Eurographics},
	keywords = {computer graphics, polygonal meshes},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2009:IPS,
	title = {Interpolatory Point Set Surfaces -- Convexity and Hermite Data},
	author = {Marc Alexa and Anders Adamson},
	url = {http://www.cg.tu-berlin.de/fileadmin/fg144/Research/Publications/pdf/hpss_tog.pdf},
	issn = {0730-0301},
	year = {2009},
	date = {2009-01-01},
	journal = {ACM Transactions on Computer Graphics},
	volume = {28},
	number = {2},
	pages = {1-10},
	publisher = {ACM},
	address = {New York, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@book{Alexa:2009:SGP,
	title = {Proceedings of the Eurographics/ACM Symposium on Geometry Processing 2009},
	editor = {Marc Alexa and Misha Kazhdan and Konrad Polthier},
	issn = {1727-8384},
	year = {2009},
	date = {2009-01-01},
	publisher = {Blackwell},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {book}
}

@article{Boubekeur:2009:MSB,
	title = {Mesh Simplification by Stochastic Sampling and Topological Clustering},
	author = {Tamy Boubekeur and Marc Alexa},
	url = {http://www.telecom-paristech.fr/~boubek/papers/TopStoc/},
	issn = {0097-8493},
	year = {2009},
	date = {2009-01-01},
	journal = {Computers and Graphics},
	volume = {33},
	number = {3},
	pages = {241 - 249},
	publisher = {Pergamon Press},
	address = {Elmsford, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Eitz:2009:PAS,
	title = {PhotoSketch: a sketch based image query and compositing system},
	author = {Mathias Eitz and Kristian Hildebrand and Tamy Boubekeur and Marc Alexa},
	url = {http://dx.doi.org/10.1145/1597990.1598050},
	year = {2009},
	date = {2009-01-01},
	booktitle = {SIGGRAPH 2009: Talks},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Hahne:2009:DIB,
	title = {Depth Imaging by Combinging Time-of-flight and on-demand stereo},
	author = {Uwe Hahne and Marc Alexa},
	editor = {Andreas Kolb and Reinhard Koch},
	url = {http://www.springerlink.com/content/01q054627663rg17/},
	year = {2009},
	date = {2009-01-01},
	booktitle = {Dynamic 3D Imaging},
	journal = {Lecture Notes in Computer Science},
	volume = {5742},
	pages = {70-83},
	publisher = {Springer Berlin / Heidelberg},
	series = {Lecture Notes in Computer Science},
	abstract = {In this paper we present a framework for computing depth images at interactive rates. Our approach is based on combining time-of-flight (TOF) range data with stereo vision. We use a per-frame confidence map extracted from the TOF sensor data in two ways for improving the disparity estimation in the stereo part: first, together with the TOF range data for initializing and constraining the disparity range; and, second, together with the color image information for segmenting the data into depth continuous areas, enabling the use of adaptive windows for the disparity search. The resulting depth images are more accurate than from either of the sensors. In an example application we use the depth map to initialize the z-buffer so that virtual objects can be occluded by real objects in an augmented reality scenario.},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@incollection{Alexa:2008:MEB,
	title = {Mesh Editing Based on Discrete Laplace and Poisson Models},
	author = {Marc Alexa and Andrew Nealen},
	editor = {José Braz and Alpesh Ranchordas and Helder Araùjo and Joaquim Jorge},
	url = {http://www.springerlink.com/content/h64p567787r71hq1/},
	isbn = {978-3-540-75272-1},
	year = {2008},
	date = {2008-01-01},
	booktitle = {Advances in Computer Graphics and Computer Vision},
	pages = {3--28},
	publisher = {Springer Berlin Heidelberg},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {incollection}
}

@article{Alexa:2008:SS,
	title = {Subdivision Shading},
	author = {Marc Alexa and Tamy Boubekeur},
	url = {http://perso.telecom-paristech.fr/~boubek/papers/SuSh/},
	issn = {0730-0301},
	year = {2008},
	date = {2008-01-01},
	journal = {ACM Transactions on Computer Graphics (SIGGRAPH Asia 2008 Proceedings)},
	volume = {27},
	number = {5},
	pages = {142:1--142:4},
	publisher = {ACM Press},
	address = {New York, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Boubekeur:2008:PhongTess,
	title = {Phong Tessellation},
	author = {Tamy Boubekeur and Marc Alexa},
	year = {2008},
	date = {2008-01-01},
	journal = {ACM Trans. Graphics (Proc. SIGGRAPH Asia)},
	volume = {27},
	number = {?},
	pages = {??-??},
	keywords = {phong tesselation},
	pubstate = {published},
	tppubtype = {article}
}

@article{Hahne:2008:CTD,
	title = {Combining Time-Of-Flight Depth and Stereo Images without Accurate Extrinsic Calibration},
	author = {Uwe Hahne and Marc Alexa},
	url = {http://www.inderscience.com/search/index.php?action=record&rec_id=21295},
	year = {2008},
	date = {2008-01-01},
	journal = {International Journal of Intelligent Systems Technologies and Applications},
	volume = {5},
	number = {3/4},
	pages = {325 - 333},
	note = {We combine a low resolution time-of-flight depth image camera based on photonic mixer devices with two standard cameras in a stereo configuration. We show that this approach is useful even without accurate calibration. In a graph cut approach, we use depth information from the low resolution time-of-flight camera to initialize the domain, and color information for accurate depth discontinuities in the high resolution depth image. The system is promising as it is low cost, and naturally extends to the setting of dynamic scenes, providing high frame rates.},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Zimmermann:2008:SC,
	title = {Sketching Contours},
	author = {Johannes Zimmermann and Andrew Nealen and Marc Alexa},
	url = {fileadmin/fg144/Research/Publications/pdf/sc_preprint.pdf},
	year = {2008},
	date = {2008-01-01},
	journal = {Computers & Graphics},
	volume = {32},
	number = {5},
	pages = {486--499},
	publisher = {Elsevier},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2007:ETE,
	title = {Extracting the essence from sets of images},
	author = {Marc Alexa},
	year = {2007},
	date = {2007-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Computational Aesthetics 2007},
	pages = {113--120},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:2007:FTS,
	title = {Fair triangulated surfaces from positional constraints at interactive rates},
	author = {Marc Alexa and Takeo Igarashi and Andrew Nealen and Olga Sorkine},
	year = {2007},
	date = {2007-01-01},
	booktitle = {Trends in Mathematical Imaging and Surface Processing},
	number = {3/2007},
	pages = {7--9},
	organization = {Mathematisches Forschungszentrum Oberwolfach},
	series = {Oberwolfach Reports},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@incollection{Alexa:2007:MLS,
	title = {Moving Least Square-based Surface Representations},
	author = {Marc Alexa},
	editor = {Markus Gross and Hanspeter Pfister},
	isbn = {978-0-12-370604-1},
	year = {2007},
	date = {2007-01-01},
	booktitle = {Point-based Graphics},
	pages = {109--126},
	publisher = {Morgan Kaufmann},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {incollection}
}

@book{Alexa:PG:2007,
	title = {Proceedings of the Pacific Graphics 2007 Conference},
	editor = {Marc Alexa and Steven Gortler and Tao Ju},
	year = {2007},
	date = {2007-01-01},
	publisher = {IEEE Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {book}
}

@inproceedings{Eitz:2007:SBI,
	title = {Sketch Based Image Deformation},
	author = {Mathias Eitz and Olga Sorkine and Marc Alexa},
	url = {http://user.cs.tu-berlin.de/~eitz/pdf/2007_sbid.pdf},
	year = {2007},
	date = {2007-01-01},
	booktitle = {Vision, Modeling and Visualization},
	pages = {135--142},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Nealen:2007:FAI,
	title = {FiberMesh: designing freeform surfaces with 3D curves},
	author = {Andrew Nealen and Takeo Igarashi and Olga Sorkine and Marc Alexa},
	issn = {0730-0301},
	year = {2007},
	date = {2007-01-01},
	journal = {ACM Trans. Graph.},
	volume = {26},
	number = {3},
	pages = {41--49},
	publisher = {ACM},
	address = {New York, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Sorkine:2007:ARA,
	title = {As-rigid-as-possible Shape Modeling},
	author = {Olga Sorkine and Marc Alexa},
	year = {2007},
	date = {2007-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Geometry Processing 2007},
	pages = {109--116},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Zimmermann:2007:SAS,
	title = {SilSketch: automated sketch-based editing of surface meshes},
	author = {Johannes Zimmermann and Andrew Nealen and Marc Alexa},
	isbn = {978-1-59593-915-3},
	year = {2007},
	date = {2007-01-01},
	booktitle = {SBIM '07: Proceedings of the 4th Eurographics workshop on Sketch-based interfaces and modeling},
	pages = {23--30},
	publisher = {ACM},
	address = {New York, NY, USA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Adamson:2006:APS,
	title = {Anisotropic Point Set Surfaces},
	author = {Anders Adamson and Marc Alexa},
	year = {2006},
	date = {2006-01-01},
	booktitle = {AFRIGRAPH 2006},
	pages = {7--14},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Adamson:2006:APSJ,
	title = {Anisotropic Point Set Surfaces},
	author = {Anders Adamson and Marc Alexa},
	year = {2006},
	date = {2006-01-01},
	journal = {Computer Graphics Forum},
	volume = {25},
	number = {4},
	pages = {717--724},
	publisher = {Blackwell Publishers},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Adamson:2006:PSC,
	title = {Point-sampled Cell Complexes},
	author = {Anders Adamson and Marc Alexa},
	year = {2006},
	date = {2006-01-01},
	journal = {ACM Transactions on Computer Graphics (SIGGRAPH 2006 Proceedings)},
	volume = {25},
	number = {3},
	pages = {671--680},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Hildenbrand:2006:CRP,
	title = {Competitive runtime performance for inverse kinematics algorithms using conformal geometric algebra},
	author = {Dietmar Hildenbrand and Daniel Fontijne and Yesheng Wang and Marc Alexa and Leo Dorst},
	year = {2006},
	date = {2006-01-01},
	booktitle = {Proceedings of the Eurographics 2004 Short Presentations},
	pages = {5--8},
	publisher = {Eurographics},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Nealen:2006:CRP,
	title = {Laplacian Mesh Optimization},
	author = {Andrew Nealen and Takeo Igarashi and Olga Sorkine and Marc Alexa},
	year = {2006},
	date = {2006-01-01},
	booktitle = {Proceedings of ACM Graphite 2006},
	pages = {381--389},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Samozino:2006:RVC,
	title = {Reconstruction with Voronoi Centered Radial Basis Functions},
	author = {Marie Samozino and Marc Alexa and Pierre Alliez and Mariette Yvinec},
	year = {2006},
	date = {2006-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Geometry Processing 2006},
	pages = {51--60},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Stoll:2006:BSP,
	title = {BSP Shapes},
	author = {Carsten Stoll and Marc Alexa and Hans-Peter Seidel},
	year = {2006},
	date = {2006-01-01},
	booktitle = {Proceedings of Shape Modeling International 2006},
	pages = {42--47},
	publisher = {IEEE Computer Society},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@book{Alexa:2005:EC,
	title = {Proceedings of the Eurographics 2005 Conference},
	editor = {Marc Alexa and Joe Marks},
	year = {2005},
	date = {2005-01-01},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {book}
}

@inproceedings{Alexa:2005:NSR,
	title = {Non-conforming surface representations},
	author = {Marc Alexa},
	editor = {Mathieu Desbrun and Helmut Pottmann},
	year = {2005},
	date = {2005-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Geometry Processing 2005},
	pages = {83--84},
	publisher = {Eurographics Association},
	note = {extended abstract of an invited talk},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Lipman:2005:LFF,
	title = {Laplacian Framework for Interactive Mesh Editing},
	author = {Yaron Lipman and Olga Sorkine and Marc Alexa and Daniel Cohen-Or and David Levin and Christian Rössl and Hans-Peter Seidel},
	year = {2005},
	date = {2005-01-01},
	journal = {International Journal of Shape Modeling},
	volume = {11},
	number = {1},
	pages = {43--62},
	publisher = {World Scientific},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Nealen:2005:ASI,
	title = {A Sketch-Based Interface for Detail-Preserving Mesh Editing},
	author = {Andrew Nealen and Olga Sorkine and Marc Alexa and Daniel Cohen-Or},
	year = {2005},
	date = {2005-01-01},
	journal = {ACM Transactions on Computer Graphics (SIGGRAPH 2005 Proceedings)},
	volume = {24},
	number = {3},
	pages = {1142-1147},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Ohtake:2005:SLI,
	title = {Sparse Low-degree Implicits with Applications to High Quality Rendering},
	author = {Yutaka Ohtake and Alexander Belyaev and Marc Alexa},
	editor = {Mathieu Desbrun and Helmut Pottmann},
	year = {2005},
	date = {2005-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Geometry Processing 2005},
	pages = {149--158},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@proceedings{Pauly:2005:ESP,
	title = {Proceedings of the ACM/Eurographics Symposium on Point-based Graphics},
	editor = {Mark Pauly and Matthias Zwicker and Marc Alexa and Szymon Rusinkiewicz},
	year = {2005},
	date = {2005-01-01},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {proceedings}
}

@article{Reuter:2005:FS,
	title = {An Improved Adjacency Data Structure for Fast Triangle Stripping},
	author = {Patrick Reuter and Johannes Behr and Marc Alexa},
	year = {2005},
	date = {2005-01-01},
	journal = {ACM Journal of Graphics Tools},
	volume = {10},
	number = {2},
	pages = {41--50},
	publisher = {AK Peters, Ltd.},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Adamson:2004:ABN,
	title = {Approximating Bounded, Non-Orientable Surfaces from Points},
	author = {Anders Adamson and Marc Alexa},
	editor = {Franca Giannini and Alexander Pasko},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of Shape Modeling International 2004},
	pages = {243--252},
	publisher = {IEEE Computer Society},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Adamson:2005:ASO,
	title = {Adaptive Sampling of Intersectable Models Exploiting Image and Object-space Coherence},
	author = {Anders Adamson and Marc Alexa and Andrew Nealen},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of 2nd International Symposium on 3D Data Processing, Visualization and Transmission},
	pages = {76--81},
	publisher = {IEEE Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@proceedings{Alexa:2004:ESI,
	title = {Proceedings of the Eurographics 2004 Short Presentations & Interactive Demos},
	editor = {Marc Alexa and Eric Galin},
	year = {2004},
	date = {2004-01-01},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {proceedings}
}

@proceedings{Alexa:2004:ESP,
	title = {Proceedings of Eurographics Symposium on Point-based Graphics},
	editor = {Marc Alexa and Markus Gross and Hanspeter Pfister and Szymon Rusinkiewicz},
	year = {2004},
	date = {2004-01-01},
	publisher = {Eurographics},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {proceedings}
}

@inproceedings{Alexa:2004:LSI,
	title = {Linear Shift-Invariant Operators for Processing Surface Meshes},
	author = {Marc Alexa},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of 2nd International Symposium on 3D Data Processing, Visualization and Transmission},
	pages = {76--81},
	publisher = {IEEE Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:2004:ONA,
	title = {On Normals and Projection Operators for Surfaces Defined by Point Sets},
	author = {Marc Alexa and Anders Adamson},
	editor = {Marc Alexa and Markus Gross and Hanspeter Pfister and Szymon Rusinkiewicz},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of Eurographics Symposium on Point-based Graphics},
	pages = {149--156},
	publisher = {Eurographics},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Klug:2004:BVF,
	title = {Bounding Volumes for Linearly Interpolated Shapes},
	author = {Tobias Klug and Marc Alexa},
	editor = {Daniel Cohen-Or and Lakhmi Jain and Nadia Magnenat-Thalmann},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of Computer Graphics International 2004},
	pages = {134--139},
	publisher = {IEEE Computer Society},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Mueller:2004:PBA,
	title = {Point Based Animation of Elastic, Plastic and Melting Objects},
	author = {Matthias Müller and Richard Kaiser and Andrew Nealen and Mark Pauly and Markus Gross and Marc Alexa},
	editor = {Ronan Boulic and Dinesh Pai},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2004},
	pages = {141--151},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Mueller:2004:VCA,
	title = {Visual Component Analysis},
	author = {Wolfgang Müller and Marc Alexa},
	editor = {Oliver Deussen and Charles Hansen and Daniel Keim and Dietmar Saupe},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Data Visualization 2004, Eurographics/IEEE TVCG Visualization Symposium Proceedings},
	pages = {129--136},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Nealen:2004:FAH,
	title = {Fast and High Quality Overlap Repair for Patch-Based Texture Synthesis},
	author = {Andrew Nealen and Marc Alexa},
	editor = {Daniel Cohen-Or and Lakhmi Jain and Nadia Magnenat-Thalmann},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of Computer Graphics International 2004},
	pages = {582--585},
	publisher = {IEEE Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Sharf:2004:CSC,
	title = {Context-based Surface Completion},
	author = {Andrei Sharf and Marc Alexa and Daniel Cohen-Or},
	year = {2004},
	date = {2004-01-01},
	journal = {ACM Transactions on Computer Graphics (SIGGRAPH 2004 Proceedings)},
	volume = {23},
	number = {3},
	pages = {878--887},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Sorkine:2004:LSE,
	title = {Laplacian Surface Editing},
	author = {Olga Sorkine and Daniel Cohen-Or and Yaron Lipman and Marc Alexa and Christian Rössl and Hans-Peter Seidel},
	editor = {Roberto Scopigno and Denis Zorin},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Geometry Processing 2004},
	pages = {179--188},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Taponecco:2004:STS,
	title = {Steerable Texture Synthesis},
	author = {Francesca Taponecco and Marc Alexa},
	editor = {Marc Alexa and Eric Galin},
	year = {2004},
	date = {2004-01-01},
	booktitle = {Proceedings of the Eurographics 2004 Short Presentations & Interactive Demos},
	pages = {57--60},
	publisher = {Eurographics Association},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Adamson:2003:AAI,
	title = {Approximating and Intersecting Surfaces from Points},
	author = {Anders Adamson and Marc Alexa},
	editor = {Leif Kobbelt and Peter Schröder and Hugues Hoppe},
	year = {2003},
	date = {2003-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Geometry Processing},
	pages = {245--254},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Adamson:2003:RTP,
	title = {Ray Tracing Point Set Surfaces},
	author = {Anders Adamson and Marc Alexa},
	editor = {Myung-Soo Kim},
	year = {2003},
	date = {2003-01-01},
	booktitle = {Proceedings of Shape Modeling International 2003},
	pages = {272--279},
	publisher = {IEEE Computer Society},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2003:CAR,
	title = {Computing and Rendering Point Set Surfaces},
	author = {Marc Alexa and Johannes Behr and Daniel Cohen-Or and Shachar Fleishman and David Levin and Claudio T. Silva},
	year = {2003},
	date = {2003-01-01},
	journal = {IEEE Transactions on Computer Graphics and Visualization},
	volume = {9},
	number = {1},
	pages = {3--15},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2003:DCF,
	title = {Differential Coordinates for Mesh Morphing and Deformation},
	author = {Marc Alexa},
	year = {2003},
	date = {2003-01-01},
	journal = {The Visual Computer},
	volume = {19},
	number = {2},
	pages = {105--114},
	publisher = {Springer},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2003:DFO,
	title = {Direction Fields over Point Sampled Geometry},
	author = {Marc Alexa and Tobias Klug and Carsten Stoll},
	editor = {Vaclav Skala},
	year = {2003},
	date = {2003-01-01},
	journal = {Journal of WSCG 2003},
	volume = {11},
	number = {1},
	pages = {27--32},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2003:SSF,
	title = {Shape Spaces from Morphing (Invited Paper)},
	author = {Marc Alexa},
	editor = {Daniel Cohen-Or and Nira Dyn and Gershon Elber and Arik Shamir},
	year = {2003},
	date = {2003-01-01},
	booktitle = {The 4th Israel-Korea Bi-0National Conference on Geometric Modeling and Computer Graphics -- Conference Proceedings},
	pages = {147--152},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Fleishman:2003:PPS,
	title = {Progressive Point Set Surfaces},
	author = {Shachar Fleishman and Daniel Cohen-Or and Marc Alexa and Claudio Silva},
	year = {2003},
	date = {2003-01-01},
	journal = {ACM Transactions on Computer Graphics},
	volume = {22},
	number = {4},
	pages = {997--1011},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Nealen:2003:HTS,
	title = {Hybrid Texture Synthesis},
	author = {Andrew Nealen and Marc Alexa},
	editor = {Per. H. Christensen and Daniel Cohen-Or},
	year = {2003},
	date = {2003-01-01},
	booktitle = {Proceedings of the Eurographics Symposium on Rendering},
	pages = {97--105},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Ohtake:2003:MPO,
	title = {Multi-level Partition of Unity Implicits},
	author = {Yutaka Ohtake and Alexander Belyaev and Marc Alexa and Greg Turk and Hans-Peter Seidel},
	year = {2003},
	date = {2003-01-01},
	journal = {ACM Transactions on Computer Graphics (SIGGRAPH 2003 Proceedings)},
	volume = {22},
	number = {3},
	pages = {463--470},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Taponecco:2003:VFV,
	title = {Vector Field Visualization using Markov Random Field Texture Synthesis},
	author = {Francesca Taponecco and Marc Alexa},
	editor = {Georges-Pierre Bonneau and Stefanie Hahmann and Chuck Hansen},
	year = {2003},
	date = {2003-01-01},
	booktitle = {Data Visualization 2003},
	pages = {195--202},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:2002:AVH,
	title = {Approximate Visual Hulls as Bounding Volumes for Occlusion Culling},
	author = {Marc Alexa and Dirk Bartz and James T. Klosowski},
	year = {2002},
	date = {2002-01-01},
	booktitle = {Poster Proceedings of IEEE Visualization},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2002:LCO,
	title = {Linear Combination of Transformations},
	author = {Marc Alexa},
	year = {2002},
	date = {2002-01-01},
	journal = {ACM Transactions on Graphics (SIGGRAPH 02 Proceedings)},
	volume = {21},
	number = {3},
	pages = {380--387},
	publisher = {ACM},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2002:LGI,
	title = {Linear Geometry Interpolation in OpenSG},
	author = {Marc Alexa and Johannes Behr},
	year = {2002},
	date = {2002-01-01},
	booktitle = {Proceedings of OpenSG Symposium 2002},
	note = {Also available as report 02i014-GRIS, Technische Universität Darmstadt},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2002:MM,
	title = {Recent Advances in Mesh Morphing},
	author = {Marc Alexa},
	year = {2002},
	date = {2002-01-01},
	journal = {Computer Graphics Forum},
	volume = {21},
	number = {2},
	pages = {173--196},
	publisher = {Blackwell},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2002:ROF,
	title = {Refinement Operators for Triangle Meshes},
	author = {Marc Alexa},
	year = {2002},
	date = {2002-01-01},
	journal = {CAGD},
	volume = {19},
	number = {3},
	pages = {169--172},
	publisher = {Elsevier},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2002:WFO,
	title = {Wiener Filtering of Meshes},
	author = {Marc Alexa},
	year = {2002},
	date = {2002-01-01},
	booktitle = {Proceedings of Shape Modeling International 2002},
	pages = {51--57},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Behr:2002:FAE,
	title = {Fast and Effective Striping},
	author = {Johannes Behr and Marc Alexa},
	year = {2002},
	date = {2002-01-01},
	booktitle = {Proceedings of OpenSG Symposium 2002},
	note = {Also available as report 02i015-ZGDV, Zentrum für Graphische Datenverarbeitung},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Taponecco:2002:SCO,
	title = {Scan Conversion of Spirals},
	author = {Francesca Taponecco and Marc Alexa},
	editor = {Vaclav Skala},
	year = {2002},
	date = {2002-01-01},
	booktitle = {Proceedings of WSCG 2002},
	pages = {115--120},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:2001:AAS,
	title = {An Animation System for User Interface Agents},
	author = {Marc Alexa and Uwe Berner and Michael Hellenschmidt and Thomas Rieger},
	editor = {V. Skala},
	year = {2001},
	date = {2001-01-01},
	booktitle = {WSCG 2001 Conference Proceedings},
	abstract = {With the advent of software agents and assistants, the concept of so called conversational user interfaces evolved, incorporating natural language interaction, dialogue management, and anthropomorphic representations. Today's challenge is to build a suitable visualization architecture for anthropomorphic conversational user interfaces, and to design believable and appropriate face-to-face interaction imitating human attributes such as emotions. The system is designed as an autonomous agent enabling easy integration into a variety of scenarios. Architecture, protocols, and graphical output are discussed.},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2001:ESI,
	title = {Editorial --- Special issue on shape blending},
	author = {Marc Alexa and Daniel Cohen-Or},
	url = {http://www.elsevier.nl/gej-ng/10/13/20/57/26/26/abstract.html; http://www.elsevier.nl/gej-ng/10/13/20/57/26/26/article.pdf},
	issn = {0097-8493},
	year = {2001},
	date = {2001-01-01},
	journal = {Computers and Graphics},
	volume = {25},
	number = {1},
	pages = {1--2},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2001:LCF,
	title = {Local control for mesh morphing},
	author = {Marc Alexa},
	editor = {Bob Werner},
	year = {2001},
	date = {2001-01-01},
	booktitle = {Proceedings of the International Conference on Shape Modeling and Applications (SMI-01)},
	pages = {209--215},
	publisher = {IEEE Computer Society},
	address = {Los Alamitos, CA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2001:MM,
	title = {Mesh Morphing STAR},
	author = {Marc Alexa},
	year = {2001},
	date = {2001-01-01},
	journal = {Eurographics 2001 State of The Art Reports},
	pages = {1--20},
	publisher = {Eurographics},
	note = {ISSN 1017-4656},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2001:PSS,
	title = {Point set surfaces},
	author = {Marc Alexa and Johannes Behr and Daniel Cohen-Or and Shachar Fleishman and David Levin and Claudio T. Silva},
	year = {2001},
	date = {2001-01-01},
	booktitle = {IEEE Visualization 2001},
	pages = {21--28},
	note = {ISBN 0-7803-7200-x},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:2001:SSF,
	title = {Shape spaces from mesh morphing},
	author = {Marc Alexa},
	editor = {Dietmar Saupe and Philipp Slusallek},
	year = {2001},
	date = {2001-01-01},
	booktitle = {Graphiktag 2001},
	publisher = {GI},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Behr:2001:VVI,
	title = {Volume Visualization in VRML},
	author = {Johannes Behr and Marc Alexa},
	editor = {Michael Capps},
	year = {2001},
	date = {2001-01-01},
	journal = {Web3D 2001 Conference},
	pages = {23--28},
	note = {ISBN 1-58113-339-1},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Mueller:2001:FWY,
	title = {Face-to-face with your assistant. Realization issues of animated user interface agents for home appliances},
	author = {Wolfgang Müller and Ulrike Spierling and Marc Alexa and Thomas Rieger},
	editor = {Thomas Kirste and Heidrun Schumann},
	year = {2001},
	date = {2001-01-01},
	journal = {Computers & Graphics},
	volume = {25},
	number = {4},
	pages = {593--600},
	publisher = {Pergamon Press / Elsevier Science},
	note = {ISSN 0097-8493},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Saupe:2001:CGI,
	title = {Computer Graphics in Germany},
	author = {Dietmar Saupe and Marc Alexa},
	year = {2001},
	date = {2001-01-01},
	journal = {Computer Graphics},
	volume = {35},
	number = {3},
	pages = {12--19},
	publisher = {ACM Press},
	note = {ISSN 0097-8930},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Weber:2001:VTO,
	title = {Visualizing Time-Series on Spirals},
	author = {Marc Weber and Marc Alexa and Wolfgang Müller},
	year = {2001},
	date = {2001-01-01},
	booktitle = {IEEE Symposium on Information Visualization 2001},
	pages = {21--28},
	note = {ISBN 0-7695-1342-5},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@article{Alexa:2000:ASI,
	title = {As-Rigid-As-Possible Shape Interpolation},
	author = {Marc Alexa and Daniel Cohen-Or and David Levin},
	editor = {Kurt Akeley},
	year = {2000},
	date = {2000-01-01},
	journal = {Proceedings of SIGGRAPH 2000},
	pages = {157--164},
	publisher = {ACM Press / ACM SIGGRAPH / Addison Wesley Longman},
	series = {Computer Graphics Proceedings, Annual Conference Series},
	note = {ISBN 1-58113-208-5},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2000:MPS,
	title = {Merging polyhedral shapes with scattered features},
	author = {Marc Alexa},
	year = {2000},
	date = {2000-01-01},
	journal = {The Visual Computer},
	volume = {16},
	number = {1},
	pages = {26--37},
	note = {ISSN 0178-2789},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Alexa:2000:RAB,
	title = {Representing Animations by Principal Components},
	author = {Marc Alexa and Wolfgang Müller},
	year = {2000},
	date = {2000-01-01},
	journal = {Computer Graphics Forum},
	volume = {19},
	number = {3},
	pages = {411--418},
	publisher = {Blackwell Publishers},
	note = {ISSN 1067-7055},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:2000:TMN,
	title = {The Morph Node},
	author = {Marc Alexa and Johannes Behr and Wolfgang Müller},
	editor = {Stephen N. Spencer},
	year = {2000},
	date = {2000-01-01},
	booktitle = {Web3D - VRML 2000 Proceedings},
	pages = {29--34},
	publisher = {ACM Press},
	note = {ISBN 1-58113-211-5},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Mueller:2000:DIF,
	title = {Design Issues for Conversational User Interfaces: Animating and Controlling 3D Faces},
	author = {Wolfgang Müller and Ulrike Spierling and Marc Alexa and Ido Iurgel},
	year = {2000},
	date = {2000-01-01},
	booktitle = {Avatars 2000},
	pages = {115--125},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Mueller:2000:EFP,
	title = {Ein flexibles Präsentationssystem für User-Interface-Agenten},
	author = {Wolfgang Müller and Marc Alexa and Thomas Rieger and Norbert Braun},
	editor = {Ulrike Spierling},
	year = {2000},
	date = {2000-01-01},
	booktitle = {Workshop Digital Storytelling (DISTEL)},
	pages = {163--175},
	publisher = {Fraunhofer IRB Verlag, Stuttgart},
	note = {ISBN 3-8167-5566-6},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Mueller:2000:FWY,
	title = {Face-to-face with your assistant. Realization issues of animated user interface agents for home appliances},
	author = {Wolfgang Müller and Ulrike Spierling and Marc Alexa and Thomas Rieger},
	editor = {Andreas Heuer and Thomas Kirste},
	year = {2000},
	date = {2000-01-01},
	booktitle = {IMC 2000. Intelligent Interactive Assistance & Mobile Multimedia Computing. Proceedings},
	pages = {77--84},
	publisher = {Neuer Hochschulschriftenverlag, Rostock},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@inproceedings{Alexa:1999:MPS,
	title = {Merging polyhedral shapes with scattered features},
	author = {Marc Alexa},
	editor = {Bob Werner},
	year = {1999},
	date = {1999-01-01},
	booktitle = {Proceedings of the International Conference on Shape Modeling and Applications (SMI-99)},
	pages = {202--210},
	publisher = {IEEE Computer Society},
	address = {Los Alamitos, CA},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@techreport{Alexa:1999:PM,
	title = {Polyhedral Morphing},
	author = {Marc Alexa},
	year = {1999},
	date = {1999-01-01},
	institution = {Technische Universität Darmstadt},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {techreport}
}

@article{Alexa:1999:TMS,
	title = {The Morphing Space},
	author = {Marc Alexa and Wolfgang Müller},
	year = {1999},
	date = {1999-01-01},
	journal = {Seventh International Conference in Central Europe on Computer Graphics and Visualization (Winter School on Computer Graphics)},
	pages = {329--336},
	note = {ISBN 80-7082-490-5. Held in University of West Bohemia, Plzen, Czech Republic, 10-14 February 1999.},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:1999:VBE,
	title = {Visualization by Examples: Mapping Data to Visual Representations Using Few Correspondences},
	author = {Marc Alexa and Wolfgang Müller},
	year = {1999},
	date = {1999-01-01},
	booktitle = {Data Visualization '99},
	pages = {23--32},
	publisher = {Springer/EG},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}

@techreport{Alexa:1998:TMS,
	title = {The Morphing Space},
	author = {Marc Alexa and Wolfgang Müller},
	year = {1998},
	date = {1998-01-01},
	institution = {Technische Universität Darmstadt},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {techreport}
}

@article{Alexa:1998:VBM,
	title = {Visualization by Metamorphosis},
	author = {Marc Alexa and Wolfgang Müller},
	year = {1998},
	date = {1998-01-01},
	journal = {Visualization '98 Late Breaking Hot Topics Proceedings},
	pages = {33--36},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@article{Mueller:1998:UMF,
	title = {Using Morphing for Information Visualization},
	author = {Wolfgang Müller and Marc Alexa},
	year = {1998},
	date = {1998-01-01},
	journal = {Workshop on New Paradigms in Information Visualization and Manipulation (NPIV '98)},
	pages = {76--79},
	publisher = {ACM Press},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {article}
}

@inproceedings{Alexa:1996:ACA,
	title = {AVWoD-Concept and Realization of Internet-Based Media Integration},
	author = {Marc Alexa and Norbert Gerfelder and Paul Grimm and Christian Seiler},
	year = {1996},
	date = {1996-01-01},
	booktitle = {Workshop Real Time Multimedia and the Web 1996},
	volume = {14},
	pages = {1--7},
	keywords = {computer graphics},
	pubstate = {published},
	tppubtype = {inproceedings}
}