Treelumination: Realistic Real-Time Illumination of Trees

The aim of the project Treelumination is to enhance the realism and visual quality of applications that need to display trees and tree-like plants in a real-time setting. This is important because realtime photo-realistic illumination effects have not been used before for rendering trees in real-time rendering applications, although they are crucial for believable high-quality rendering. The effects that we are going to consider include shadows and self-shadowing, translucency of leaves, global illumination and high-dynamic range rendering. Trees and similar plants like bushes or shrubs are a very important element of outdoor scenery. This holds true especially for applications that require interactive walkthroughs or manipulation of a scene. Such applications include visual impact analysis, driving and traffic simulation, design reviews, and computer games to name but a few. Unfortunately, trees and vegetation belong to the most difficult class of objects to render realistically, let alone fast, owing to their high geometric and animation complexity. This proposal is concemed with the fast illumination of trees in a way that does not preclude animation. The illumination of trees consists of several important factors: Outdoor illumination due to direct sunlight and skylight illumination, diffuse interreflections due to the leaf structure, anisotropies and texture for leaves, and, very importantly, the translucency of leaves, which is most notable an sunlit days. Finally, orte of the most important aspects of tree illumination is the effect of shadows cast an the ground and an the leaves themselves. Although some of these illumination effects have been successfully modeled and simtrlated in offline rendering, it seems that most of them have been practically ignored in interactive and realtime rendering. Therefore, the goal of the Treelumination project is to bridge the gap between photo-realistic and real-time rendering for the display of trees, while still maintaining reasonable capabilities for animation. lt is the restriction towards trees that will make it possible to achieve this goal and overcome previous restrictions. We plan our algorithms to be applicable for different geometric representations of trees, ranging from close-up views of individual leaves to far-away views where trees are represented by textured quads (and where many effects can be simplified), so that our results can be seamlessly integrated with existing real-time tree rendering packages.