Research On The Theory And Application Of Global Illumination With Reflections Refractions And Caustics Rendering

Global illumination is a vital part of realistic image synthesis. With the rapiddevelopment of graphics applications, it becomes a challenge to ask the globalillumination methods to render photorealistic images in realtime. Current researches onglobal illumination cannot render multiple global illumination effects interactively forscenes with both large geometries and fully dynamic animations. In this dissertation,based on the survey on interactive realistic rendering, we propose an interactive globalillumination approach, which simulates reflections, refractions, caustics, and diffuseinter-reflections simultaneously for large and dynamic scenes. The approach provides acomplete rendering process on the GPU. In the experiments, the validity of the approachis verified. The contributions of the work are summarized as follows.For the bottleneck of indirect occlusion tests, we first study the way to dynamicallyconstruct the volume-based accelerating structure. In this work, we propose a real-timebinary voxelization which may be the fastest voxelization method until now. Thevoxelization can get high-quality voxel-represented scenes with less error and using lessmemory storage. We also introduce the way to build a hierarchical structure on thevoxels. With its help, rays stop marching early and we find the intersections of the rayand objects in the scene fast.Based on the hierarchically organized voxels, the dissertation extends the work ofvoxel-based near-filed indirect illumination described in the VGI and proposes areal-time indirect illumination method by the near-far irradiance decomposition. In thiswork proposed a multi-resolutional gathering and a multi-pass geometric basedup-sampling is to get higher performance. It is proved in the experiment that for largedynamic scenes, the method can get high realistic images in a speed of more than20frames per second.For global illumination with reflections, refractions and caustics, the dissertationprovides an approach to simulate low-frequency lights, high-frequency lights and theirinteraction effects. The method can render interactively. Even compared with the fastGPU-acclerated photon mapping, it renders2~5times faster.The dissertation also analyzes and solves the problem of the artifacts caused by the approximation in the image-based caustic rendering. Based on the concept of virtualobjects in the optical maping theory, we introduce the virtual-object-based photon beamtracing for caustic rendering. Taking advantages of GPU techniques, the method canfind the correct positions of photons fast by the geometry transformation computation.The method also introduces the path-based photon mapping to construct causticmapping. For complex geometry-based scenes, the method elliminates artifacts causedby undersampling and renders caustics caused by multi-bounces reflections orrefractions realistically.Finally, the dissertation explores the way to render large-scale geometry data inparallel using a distributed clustered system. We propose a fast NPU-based imagecomposition for the sort-last parallel rendering system, called NPUPR. NPUPR hasgood load-balance, low parallel cost and scalable features. It can be applied to a widerange of applications.