People

Research

Real-time physics simulations are becoming increasingly important in the entertainment industry: Computer games already make extensive use of rigid-body simulations and have started to include elasticly deformable bodies. Fluid simulations, however, have so far been limited to a 2D reduction (shallow water waves) of the Navier-Stokes equations. Sound effects are rarely computed in real time but instead are typically realized by playing back pre-recorded samples. In the future, as other aspects of games become more realistic, demand will increase for real-time physics simulations. Physics simulation is also heavily used in the production of animations for feature films. Here, of course, the final rendering can be done more elaborately, with CPU- intensive simulations off-line. But the initial design phase is much more cost-effective if it utilizes the possibility of real-time simulations.
A third area with great potential is scientific visualization, where adding realistic physics can greatly enhance the immersive quality of virtual reality environments. All of these applications depend crucially on the availabilty of suitable mathematical algorithms. The requirements for these algorithms are substantially different from those common in numerical analysis. There is a fixed time budget (about 10 ms) for each time step. Furthermore, due to unpredictable user interactions the algorithms have to be extremely robust. Accuracy is less important than usual, but still, the qualitative behaviour of the objects should be in accordance with physics. For example, conservation laws should be respected and one should not achieve robustness merely by introducing an unnatural amount of damping.
These requirements make this area ideal for applications of the paradigm of Discrete Differential Geometry: Discretizations coming from a discrete theory that incorporates the structure of the smooth theory (instead of merely trying to approximate the solutions) quite often capture to a large extent the qualitative features of the continuous models even with very coarse discretizations and large time steps.

Facilities and Software

the PORTAL: parallel optical research testbed and laboratory

The PORTAL is a three wall CAVE^TM like virtual reality theater at the institute for mathematics, TU Berlin.
It allows mathematicians and other scientists to investigate complicated structures in a way that is vastly superior to the flat screens of a workstation.

The PORTAL is mostly driven by jReality, but there are also applications using Amira as well as Syzygy -- a toolkit for virtual reality on pc clusters.

The PORTAL consists of three back projection screens and a magnetic motion tracking system. Each screen is driven by two projectors for stereo viewing. The motion tracking system tracks the position of the head plus an extra input device (wand or game pad).

jReality: a multi target 3d viewer in Java

jReality is a Java class library for interactive 3D visualization on a wide variety of platforms. It supports a variety of output forms: software-only rendering, OpenGL rendering, immersive virtual reality (as in CAVEs) rendering; as well as file formats like Pixar's RenderMan® and SVG.

Recent Publications

S. Weißmann, U. Pinkall. Real-time initeractive simulation of smoke using discrete integrable vortex filaments. In Proceedings of 6th Workshop on Virtual Reality Interaction and Physical Simulation VRIPHYS 09 (Nov. 5-6, Karlsruhe, Germany).

S. Weißmann, C. Gunn, P. Brinkmann, T. Hoffmann, U. Pinkall. jReality: a java library for real-time interactive 3D graphics and audio. In Proceedings of 17th International ACM Conference on Multimedia 2009 (Oct. 19-24, Beijing, China).

P. Brinkmann, S. Weißmann. Real-time Interactive 3D Audio and Video with jReality. In Proceedings of the International Computer Music Conference ICMC 2009 (Aug. 19-21, Montreal, Canada).