Interactive particle tracing in dynamic scenes consisting of NURBS surfaces

Simulating the distribution of light in virtual environments to generate photorealistic images has become increasingly important for numerous applications in the field of computer graphics. Nevertheless, the off-line rendering of special effects for the film industry or visualizations for education, architecture, and engineering quite often takes minutes or even hours for a single frame. Especially in the context of dynamic scenes with freeform surfaces, simulating global illumination with interactive frame rates is very valuable; however, still challenging. Exploiting temporal coherences in lighting simulations yields a promising and feasible solution to optimize computing time by selectively updating scene regions with outdated illumination. We present a novel particle tracing method using multidimensional Halton sequences on top of direct ray tracing of dynamic scenes consisting of NURBS surfaces. Interactive frame rates are delivered without triangulation by carefully optimized intersection tests with NURBS surfaces and the support of multi-core processors. The implementation benefits from parallelization with SIMD operations due to quasi-random sampling of highly coherent particle packets with Halton numbers. Geometrical changes in the scene are handled by selectively deleting and retracing the affected particles yielding up to 75% faster particle tracing in comparison to computing a complete new lighting simulation. Finally, our method supports real-time adjustments of physical quantities, e.g. the spectral distribution of light spectra or surface reflectances.