Realistic Illumination of Vegetation in Real-Time Environments

In this paper we show how to combine and extend state-of-the-art computer graphics algorithms for realistic illumination of vegetation. Our main target are real-time rendering environments, namely the Lenné3D visualization system. We focus on plants near the viewer where we separate the rendering equation to model the different lighting effects: Direct sun light is handled by advanced fragment shaders and shadow mapping whereas indirect light is calculated from environment maps and precomputed radiance transfer (PRT). This way we can handle both low and high frequency lighting. Soft shadows and diffuse indirect lighting are contributed by the PRT, hard shadows, diffuse, glossy and specular direct lighting are calculated using the common rendering pipeline including shaders. We assume static scenes (fixed terrain and plant positions, fixed lighting) to precompute the radiance transfer. Note that this does not introduce view dependence. Our main contribution is the extension of these algorithms to large scenes with a very high number of objects. Previous work usually covered illumination of single objects. Scene complexity was hidden by environments maps. In large scenes, one environment map does not fit all objects due to neighboring objects occluding parts of the outer scene environment. This also introduces a source of indirect lighting among different plants. We propose a new method of clustering and interpolating environment maps to handle the varying local environments of the plants.