Real-time Global Illumination For Dynamic Scenes

Global illumination plays an important role in 3D graphics. Compared with local illumination, global illumination considers not only direct lighting, but also influence from indirect lights and occlusion. Thus, it can simulate more realistic effects, for instance, refraction and reflection of transparent objects, sub-surface scattering of translucent objects and shadow. As its calculation complexity is far more than that of local illumination, there has been yet few satisfying solution which achieves high quality and performance simultaneously. Although researchers have proposed many acceleration approaches towards ray tracing, radiosity, photon mapping et c, real-time frame rates is far from achieved, say nothing of interactive applications as video games, virtual reality and so on. Recently developed precomputed techniques partly solved this problem for static scenes, but are not suitable for dynamic scenes.Since 2000, computer graphics has been promoted greatly by GPU (Graphics Process Unit). Although GPU's SIMD (Single Instruction Multiple Data) structure limits its flexibility, it also makes GPU have far higher parallel speed than CPU. In this paper, we take advantage of GPU to accelerate global illumination of dynamic scenes, including:We present an improved second-refraction calculation approach for dynamic transparent objects. We also introduce a technique of reference point bias in environment mapping.We propose a two-pass sub-surface scattering rendering methods based on render-to-textures technique, which can display dynamic translucent objects interactively.We present a real-time anisotropic occlusion calculation approach by means of a spherical harmonic compression scheme, facilitating real-time and high-quality shadow simulation.