Welcome
From our Architectural Geometry project: Rationalization of TriangleBased PointFolding Structures
From our Simulation project: Wave Propagation using the Photon Path Map
From our Image Representation and Manipulation project: TwoColored Pixels
From our project: Generalized Use of NonTerminal Symbols for Procedural Modeling
From our student project: Super Smash Panda
Gottfried Wilhelm Leibniz Prize 2014 Ceremony
Welcome to the Computer Graphics Group at RWTH Aachen University!
The research and teaching activities at our institute focus on geometry acquisition and processing, on interactive visualization, and on related areas such as computer vision, photorealistic image synthesis, and ultra high speed multimedia data transmission.
In our projects we are cooperating with various industry companies as well as with academic research groups around the world. Results are published and presented at highprofile conferences and symposia. Additional funding sources, among others, are the Deutsche Forschungsgemeinschaft and the European Union.
News
•  Zometool Shape Approximation We have two new publications (TVCG 2014 and GMOD/GMP 2014) on freeform shape approximation using the Zometool system.
Please see the project page for more information.  April 7, 2014 
•  Demos at the Mobile World Congress 2014 We will present two demos at the Mobile World Congress 2014 in Barcelona from 24  27 of February. In Hall 6, booth B40 we will present the latest version of our Mobile Multi Display as well as a system for 3D city reconstructions based on crowd sourced photos. For more information see the news at the ICE Institute.  Feb. 20, 2014 
•  Prof. Dr. Kobbelt receives important German research award Prof. Dr. Kobbelt receives the Gottfried Wilhelm Leibniz Prize. As Germany’s most important research award its goal is to help outstanding scientists in their research. More information can be found here.  Dec. 6, 2013 
•  We have a paper at the ICCV 2013 Workshop on Big Data in 3D Computer Vision.  Nov. 29, 2013 
•  The preprint of our AAG12 mesh planarization paper is now available  Oct. 17, 2013 
•  We have a paper at SIGGRAPH Asia 2013.  Aug. 26, 2013 
Recent Publications
IntegerGrid Maps for Reliable Quad MeshingSIGGRAPH 2013 Quadrilateral remeshing approaches based on global parametrization enable many desirable mesh properties. Two of the most important ones are (1) high regularity due to explicit control over irregular vertices and (2) smooth distribution of distortion achieved by convex variational formulations. Apart from these strengths, stateoftheart techniques suffer from limited reliability on realworld input data, i.e. the determined map might have degeneracies like (local) noninjectivities and consequently often cannot be used directly to generate a quadrilateral mesh. In this paper we propose a novel convex MixedInteger Quadratic Programming (MIQP) formulation which ensures by construction that the resulting map is within the class of so called IntegerGrid Maps that are guaranteed to imply a quad mesh. In order to overcome the NPhardness of MIQP and to be able to remesh typical input geometries in acceptable time we propose two additional problem specific optimizations: a complexity reduction algorithm and singularity separating conditions. While the former decouples the dimension of the MIQP search space from the input complexity of the triangle mesh and thus is able to dramatically speed up the computation without inducing inaccuracies, the latter improves the continuous relaxation, which is crucial for the success of modern MIQP optimizers. Our experiments show that the reliability of the resulting algorithm does not only annihilate the main drawback of parametrization based quadremeshing but moreover enables the global search for highquality coarse quad layouts – a difficult task solely tackled by greedy methodologies before. 

QEx: Robust Quad Mesh ExtractionSIGGRAPH Asia 2013 The most popular and actively researched class of quad remeshing techniques is
the family of parametrization based quad meshing methods. They all strive
to generate an integergrid map, i.e. a parametrization of the input surface
into R^{2} such that the canonical grid of integer isolines forms a
quad mesh when mapped back onto the surface in R^{3}. An essential,
albeit broadly neglected aspect of these methods is the quad extraction
step, i.e. the materialization of an actual quad mesh from the mere “quad
texture”. Quad (mesh) extraction is often believed to be a trivial matter but
quite the opposite is true: Numerous special cases, ambiguities induced by
numerical inaccuracies and limited solver precision, as well as imperfections
in the maps produced by most methods (unless costly countermeasures are taken)
pose significant challenges to the quad extractor. We present a method to
sanitize a provided parametrization such that it becomes numerically
consistent even in a limited precision floating point representation. Based
on this we are able to provide a comprehensive and sound description of how to
perform quad extraction robustly and without the need for any complex
tolerance thresholds or disambiguation rules. On top of that we develop a
novel strategy to cope with common local foldovers in the parametrization.
This allows our method, dubbed QEx, to generate allquadrilateral meshes
where otherwise holes, nonquad polygons or no output at all would have been
produced. We thus enable the practical use of an entire class of maps that was
previously considered defective. Since state of the art quad meshing methods
spend a significant share of their run time solely to prevent local
foldovers, using our method it is now possible to obtain quad meshes
significantly quicker than before. We also provide libQEx , an open source
C++ reference implementation of our method and thus significantly lower the
bar to enter the field of quad meshing. 

Efficient Enforcement of Hard Articulation Constraints in the Presence of Closed Loops and ContactsEurographics 2014 In rigid body simulation, one must distinguish between contacts (socalled unilateral constraints) and articulations (bilateral constraints). For contacts and friction, iterative solution methods have proven most useful for interactive applications, often in combination with ShockPropagation in cases with strong interactions between contacts (such as stacks), prioritizing performance and plausibility over accuracy. For articulation constraints, direct solution methods are preferred, because one can rely on a factorization with linear time complexity for treelike systems, even in illconditioned cases caused by large massratios or high complexity. Despite recent advances, combining the advantages of direct and iterative solution methods wrt. performance has proven difficult and the intricacy of articulations in interactive applications is often limited by the convergence speed of the
iterative solution method in the presence of closed kinematic loops (i.e. auxiliary constraints) and contacts.
We identify common performance bottlenecks in the dynamic simulation of unilateral and bilateral constraints
and are able to present a simulation method, that scales well in the number of constraints even in illconditioned
cases with frictional contacts, collisions and closed loops in the kinematic graph. For cases where many joints are connected to a single body, we propose a technique to increase the sparsity of the positive definite linear system.
A solution to these bottlenecks is presented in this paper to make the simulation of a wider range of mechanisms possible in realtime without extensive parameter tuning. 