A lighting model for fast rendering of forest ecosystems

Real-time rendering of large-scale, forest ecosystems remains a challenging problem, in that important global illumination effects, such as leaf transparency and inter-object light scattering, are difficult to capture, given tight timing constraints and models that typically contain hundreds of millions of primitives. This paper proposes a new lighting model, adapted from a model previously used to light convective clouds and other participating media, together with a distribution of ray processing across multiple GPUs, in order to achieve these global illumination effects while maintaining near real-time performance. The lighting model is based on a lattice-Boltzmann method in which reflectance, transmittance, and absorptance parameters are taken from measurements of real plants. The lighting model is solved as a pre-processing step and requires only seconds on a single GPU. The ray tracing engine uses the well-known short-stack algorithm, due to Horn, Sugerman, Houston, and Hanrahan. Both the pre-processing step and the ray tracing engine make extensive use of NVIDIApsilas compute unified device architecture (CUDA).