Welcome



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, photo-realistic 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 high-profile conferences and symposia. Additional funding sources, among others, are the Deutsche Forschungsgemeinschaft and the European Union.

News

Prof. Dr. Leif Kobbelt has been elected a full member of the North Rhine-Westphalian Academy of Sciences, Humanities and the Arts

The North Rhine-Westphalian Academy of Sciences, Humanities and the Arts is an association of the leading scientists in North Rhine-Westphalia. The Academy was founded in 1970 as the successor institution to the Arbeitsgemeinschaft für Forschung of the Federal State of North Rhine-Westphalia, which had been founded in 1950 by the then Premier of the Federal State, Karl Arnold, to provide advice to the State Government in the reconstruction of the State after its devastation in the war. For further information about the Academy, please visit its homepage.

March 30, 2016

We have a paper on Improved Surface Quality in 3D Printing by Optimizing the Printing Direction at Eurographics 2016.

Feb. 18, 2016

We have a paper on Adapting Feature Curve Networks to a Prescribed Scale at Eurographics 2016.

Feb. 16, 2016

The new webpage of the Aachen Cathedral

The new webpage of the Aachen Cathedral has been launched. A central feature of this new web experience is an interactive virtual tour in 3D which is based on methods and algorithms for 3D reconstruction and efficient photorealistic rendering developed by the Computer Graphics group at the Visual Computing Institute. Web concept, technology, and implementation have been done by the Interactive Pioneers. More information about the 3D reconstruction and rendering process can be found here.

Jan. 29, 2016

Leif Kobbelt gave an invited talk at the Symposium on Geometry and Computational Design in Vienna.

Nov. 30, 2015

Leif Kobbelt gave an invited keynote presentation at the 24th International Meshing Roundtable in Austin, TX.

Oct. 15, 2015

Recent Publications

Non-Linear Shape Optimization Using Local Subspace Projections

SIGGRAPH 2016

In this paper we present a novel method for non-linear shape opti- mization of 3d objects given by their surface representation. Our method takes advantage of the fact that various shape properties of interest give rise to underdetermined design spaces implying the existence of many good solutions. Our algorithm exploits this by performing iterative projections of the problem to local subspaces where it can be solved much more efficiently using standard numer- ical routines. We demonstrate how this approach can be utilized for various shape optimization tasks using different shape parameteri- zations. In particular, we show how to efficiently optimize natural frequencies, mass properties, as well as the structural yield strength of a solid body. Our method is flexible, easy to implement, and very fast.

 

HexEx: Robust Hexahedral Mesh Extraction

SIGGRAPH 2016

State-of-the-art hex meshing algorithms consist of three steps: Frame-field design, parametrization generation, and mesh extraction. However, while the first two steps are usually discussed in detail, the last step is often not well studied. In this paper, we fully concentrate on reliable mesh extraction. Parametrization methods employ computationally expensive countermeasures to avoid mapping input tetrahedra to degenerate or flipped tetrahedra in the parameter domain because such a parametrization does not define a proper hexahedral mesh. Nevertheless, there is no known technique that can guarantee the complete absence of such artifacts. We tackle this problem from the other side by developing a mesh extraction algorithm which is extremely robust against typical imperfections in the parametrization. First, a sanitization process cleans up numerical inconsistencies of the parameter values caused by limited precision solvers and floating-point number representation. On the sanitized parametrization, we extract vertices and so-called darts based on intersections of the integer grid with the parametric image of the tetrahedral mesh. The darts are reliably interconnected by tracing within the parametrization and thus define the topology of the hexahedral mesh. In a postprocessing step, we let certain pairs of darts cancel each other, counteracting the effect of flipped regions of the parametrization. With this strategy, our algorithm is able to robustly extract hexahedral meshes from imperfect parametrizations which previously would have been considered defective. The algorithm will be published as an open source library.

 

Reduced-Order Shape Optimization Using Offset Surfaces

ACM Transactions on Graphics (TOG), 34(4), 2015
Proceedings of the 2015 SIGGRAPH Conference

Given the 2-manifold surface of a 3d object, we propose a novel method for the computation of an offset surface with varying thickness such that the solid volume between the surface an its offset satisfies a set of prescribed constraints and at the same time minimizes a given objective functional. Since the constraints as well as the objective functional can easily be adjusted to specific application requirements, our method provides a flexible and powerful tool for shape optimization. We use manifold harmonics to derive a reduced-order formulation of the optimization problem which guarantees a smooth offset surface and speeds up the computation independently from the input mesh resolution without affecting the quality of the result. The constrained optimization problem can be solved in a numerically robust manner with commodity solvers. Furthermore, the method allows to simultaneously optimize an inner and an outer offset in order to increase the degrees of freedom. We demonstrate our method in a number of examples where we control the physical mass properties of rigid objects for the purpose of 3d printing.

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