Thorsten Scheuermann

Physically-based visual simulation on graphics hardware

In this paper, we present a method for real-time visual simulation of diverse dynamic phenomena using programmable graphics hardware. The simulations we implement use an extension of cellular automata known as the coupled map lattice (CML). CML represents the state of a dynamic system as continuous values on a discrete lattice. In our implementation we store the lattice values in a texture, and use pixel-level programming to implement simple next-state computations on lattice nodes and their neighbors. We apply these computations successively to produce interactive visual simulations of convection, reaction-diffusion, and boiling. We have built an interactive framework for building and experimenting with CML simulations running on graphics hardware, and have integrated them into interactive 3D graphics applications.In this paper, we present a method for real-time visual simulation of diverse dynamic phenomena using programmable graphics hardware. The simulations we implement use an extension of cellular automata known as the coupled map lattice (CML). CML represents the state of a dynamic system as continuous values on a discrete lattice. In our implementation we store the lattice values in a texture, and use pixel-level programming to implement simple next-state computations on lattice nodes and their neighbors. We apply these computations successively to produce interactive visual simulations of convection, reaction-diffusion, and boiling. We have built an interactive framework for building and experimenting with CML simulations running on graphics hardware, and have integrated them into interactive 3D graphics applications.

Fast Summed-Area Table Generation and its Applications

We introduce a technique to rapidly generate summed-area tables using graphics hardware. Summed area tables, originally introduced by Crow, provide a way to filter arbitrarily large rectangular regions of an image in a constant amount of time. Our algorithm for generating summed-area tables, similar to a technique used in scientific computing called recursive doubling, allows the generation of a summed-area table in O(log n) time. We also describe a technique to mitigate the precision requirements of summed-area tables. The ability to calculate and use summed-area tables at interactive rates enables numerous interesting rendering effects. We present several possible applications. First, the use of summed-area tables allows real-time rendering of interactive, glossy environmental reflections. Second, we present glossy planar reflections with varying blurriness dependent on a reflected object’s distance to the reflector. Third, we show a technique that uses a summed-area table to render glossy transparent objects. The final application demonstrates an interactive depth-of-field effect using summedarea tables.

Practical real-time hair rendering and shading

We present a real-time algorithm for hair rendering using a polygon model, which was used in the real-time animation Ruby: The Double Cross, appearing in this year’s SIGGRAPH animation festival. The hair shading model is based on the Kajiya-Kay model, and adds a real-time approximation of realistic specular highlights as observed by Marschner et al. We also describe a simple technique to render the semi-transparent hair model in approximate back-to-front order. Instead of executing a spatial sorting step on the CPU at run-time, we render the opaque and transparent hair regions in separate passes to resolve visibility.

Interactive summed-area table generation for glossy environmental reflections

There are many applications in computer graphics where spatially varying filters are useful. One example is the rendering of glossy reflections. Unlike perfectly reflective materials, which only require a single radiance sample in the direction of the reflection vector, glossy materials require integration over a solid angle. Blurring by filtering the reflected image with a support dependent on the surface‘s BRDF can approximate this effect. This is currently done by pre-filtering off-line, which limits the technique to static environments. Crow [1984] introduced summed-area tables to enable more general texture filtering than was possible with mip maps. Once generated, a summed-area table provides a means to evaluate a spatially varying box filter with a constant number of texture reads.

Physiological reaction and presence in stressful virtual environments

A common metric of VE quality is presence --- the degree to which the user feels like they are in the virtual scene as opposed to the real world. Presence is important for many VE applications [Hodges et al. 1994]. Since presence is a subjective condition, it is most commonly measured by self-reporting, either during the VE experience or immediately afterwards by questionnaires. There is vigorous debate in the literature as to how to best measure presence [Meehan 2001].