XGRT - Extensible Graphics Toolkit

XGRT is an object-oriented framework for computer graphics applications, especially in the area of geometry processing. It offers interactive editing of large out-of-core point clouds and a number of geometry processing algorithms. more...

Inverse Procedural Modeling

Inverse procedural modeling refers to the process of estimating rules how to build a shape from one or more example shapes. In this project, we are looking at fully automatic techniques that can derive shape grammars from single example shapes. We use partial symmetries of an object to find a grammatic that describes a family of shapes that are provably similar to the exemplar in a strict formal sense.

Key Publications

• M. Bokeloh, M. Wand, H.-P. Seidel: A Connection between Partial Symmetry and Inverse Procedural Modeling. In: ACM Transactions on Graphics (Siggraph 2010).
  project page, paper (high-res, 24MB), paper (low-res, 1.8MB), video (Youtube)
   
• M. Bokeloh, M. Wand, V. Koltun, H.-P. Seidel: "Pattern-Aware Deformation Using Sliding Dockers", In: ACM Transactions on Graphics (Proc. Siggraph Asia), 2011.
  project page, paper (preprint, PDF, 22MB), video (mp4, 72MB)
  

Symmetry Detection

Given a 3D model, we would like to compose this model into elementary building blocks. Each building block consists of the same geometry up to a certain transformation (rigid motion, isometry, more general deformation) and possibly noise. We are looking at algorithms that can compute such decompositions fully automatically, without user supervision.

Key Publications

• M. Bokeloh, A. Berner, M.Wand, H.-P. Seidel, A. Schilling: Symmetry Detection Using Line Features. In: Computer Graphics Forum, Proc. Eurographics '09.
  paper (10 MB), video: avi/xvid (40MB) quicktime (32MB), project page (link).
   
• A. Berner, M. Bokeloh, M.Wand, A. Schilling, H.-P. Seidel: A Graph-Based Approach to Symmetry Detection. In: Proc. Symposium on Point-Based Graphics, 2008.
  paper (1 MB), project page (link)
   
• A. Berner, M. Bokeloh, M. Wand, A. Schilling, H.-P. Seidel: Generalized Intrinsic Symmetry Detection. In: MPI Informatik Tech Report MPI-I-2009-4-005, 2009.
  paper (6MB)

Deformable Shape Matching

The goal of this project is to find dense correspondences between deformed shapes. We assume that the deformation the shape has undergone is intrinsically isometric, i.e., does not change geodesic distances within the deformed surface. However, we have to address the problem of topological noise (partial data, acquisition holes, apparant connections if for example the hand of a person gets to close to the body). We are looking at algorithms that can perform global isometric shape matching witout prior initialization and under topological noise.

Key Publications

• A. Tevs, A. Berner, M. Wand, I. Ihrke, H.-P. Seidel: Intrinsic Shape Matching by Planned Landmark Sampling. In: Computer Graphics Forum (Proc. Eurographics), 2011.
  project page (link), paper (20MB)
   
• A. Tevs, M. Bokeloh, M.Wand, A. Schilling, H.-P. Seidel: Isometric Registration of Ambiguous and Partial Data. In: Proc. IEEE Conference on Computer Vision and Pattern Recognition (CVPR '09), 2009.
  paper (2 MB), video (mp4, 30MB)

Animation Reconstruction

In this project, we consider sequences of point clouds that shows a deformable shape in motion, as obtained from real-time 3D scanners. This means we have typically acquisition holes so that the shape is only shown partially in each frame. In addition, no correspondence information is given by the data. Our goal is to reconstruct shape and motion simultaneously, including dense correspondences over time and completed geometry in every frame that matches the data and behaves plausibly in unobserved areas. We refer to this problem setting as animation reconstruction.

Key Publications

• A. Tevs, A. Berner, M. Wand, I. Ihrke, M. Bokeloh, J. Kerber, H.-P. Seidel: "Animation Cartography - Intrinsic Reconstruction of Shape and Motion", In: ACM Transactions on Graphics, 2011.
  project page (link), paper (10MB), video (mp4, 290MB)
   
• M. Wand, B. Adams, M. Ovsjanikov, A. Berner, M. Bokeloh, P. Jenke, L. Guibas, H.-P. Seidel, A. Schilling: Efficient Reconstruction of Non-rigid Shape and Motion from Real-Time 3D Scanner Data. In: ACM Transactions on Graphics 28(2), April 2009.
  paper (8 MB), video: avi/xvid (56MB), quicktime (66MB); copyright: ACM.
   
• B. Adams, M. Ovsjanikov, M. Wand, H.-P. Seidel, L. J. Guibas: Meshless Modeling of Deformable Shapes and their Motion. In: ACM SIGGRAPH/Eurographics Symposium on Computer Animation, 2008.
  paper (4 MB), video (Youtube)
   
• M. Wand, P. Jenke, Q. Huang, M. Bokeloh, L. Guibas, and A. Schilling: Reconstruction of Deforming Geometry from Time-Varying Point Clouds. In: Proc. 5th Eurographics Symposium on Geometry Processing, Barcelona, Spain, pp. 49-58, 2007.
  paper (0.6 MB), video (DivX, 36 MB)
   

Algorithms and Data Structures for Large Scene Modeling

In this project we consider the problem of handling large amounts of geometric data. We have developed a new data structure that allows for real-time editing and visualization of large out-of-core 3D data sets, with size limited only by available hard disc space. We have also developed an open and modular system architecture that uses this data structure as an abstract geometric data base to implement a real-time large scene editor application, supporting interactive local editing, various streaming geometry processing algorithms, and large animation sequences.

Key Publications

• M. Wand, A. Berner, M. Bokeloh, A. Fleck, M. Hoffmann, P. Jenke, B. Maier, D. Staneker, A.Schilling: Interactive Editing of Large Point Clouds. In: Proc. Symposium on Point-Based Graphics (PBG 07), 2007.
  paper (3.9 MB), video (DivX, 46 MB)
   
• M. Wand, A. Berner, M. Bokeloh, P. Jenke, A. Fleck, M. Hoffmann, B. Maier, D. Staneker, A.Schilling, H.-P. Seidel: Processing and Interactive Editing of Huge Point Clouds from 3D Scanners. In: Computer and Graphics, 2008.
   
• Software: The XGRT system - this is a complete point cloud processing software framework with graphics user interface that can handle very large data sets interactively.
  Project page and download (binary & source code, GPL)

Statistical Shape Spaces and 3D Reconstruction

The goal of this project is to describe statistical probability distributions on shape that assign different likelihoods for different types of shapes. The resulting framework is used to device a Bayesian geometry reconstruction algorith: It infers the most likely original shape given a noisy measurment (in the sense of maximizing the posterior propability density for a given statistic measurment model and user defined shape priors).

Key Publications

• P. Jenke., M. Wand, M. Bokeloh, A. Schilling, W. Strasser: Bayesian Point Cloud Reconstruction. In: Computer Graphics forum 25(3), 379-388 (Proc. Eurographics 2006), 2006.
  paper (3.5 MB)
   
• Q.-X. Huang, B. Adams, M. Wand: Bayesian Surface Reconstruction via Iterative Scan Alignment to an Optimized Prototype. In: Proc. 5th Eurographics Symposium on Geometry Processing, Barcelona, Spain, 2007.
  paper (21 MB)

Efficient Stochastic Synthesis for 3D Modeling

The goal of this project was to investigate the inverse problem: Rather than analysing real-world geometry to detect statistical pattern, we use a generative stochastical model to create objects procedurally. We develop a new hierarchical, bounded support subdivision, multi-channel geometry synthesis technique that is able to create complex, non-stationary fractal objects in an intuitive way. By specifying some simple multi-variate subdivision rules, models ranging from smooth patches to complex landscape models can be created. Due to a GPU implementation, the technique works in real-time, allowing to zoom into objects with virtually infinite detail.

Key Publication

• M. Bokeloh., M. Wand: Hardware Accelerated Multi-Resolution Geometry Synthesis. In: Symposium on Interactive 3D Graphics and Games 2006.
  paper (4.6 MB), video, (DivX 24MB)