A graphics processing unit based method for dynamic real-time global illumination

摘要

Real-time realistic image synthesis for virtual environments has been one of the most actively researchedudareas in computer graphics for over a decade. Images that display physically correct illumination of anudenvironment can be simulated by evaluating a multi-dimensional integral equation, called the renderingudequation, over the surfaces of the environment. Many global illumination algorithms such as pathtracing,udphoton mapping and distributed ray-tracing can produce realistic images but are generally unableudto cope with dynamic lighting and objects at interactive rates. It still remains one of most challengingudproblems to simulate physically correctly illuminated dynamic environments without a substantial preprocessingudstep.udIn this thesis we present a rendering system for dynamic environments by implementing a customizedudrasterizer for global illumination entirely on the graphics hardware, the Graphical ProcessingudUnit. Our research focuses on a parameterization of discrete visibility field for efficient indirect illuminationudcomputation. In order to generate the visibility field, we propose a CUDA-based (ComputeudUnified Device Architecture) rasterizer which builds Layered Hit Buffers (LHB) by rasterizing polygonsudinto multi-layered structural buffers in parallel. The LHB provides a fast visibility function for any directionudat any point. We propose a cone approximation solution to resolve an aliasing problem due toudlimited directional discretization. We also demonstrate how to remove structure noises by adapting anudinterleaved sampling scheme and discontinuity buffer. We show that a gathering method amortized withuda multi-level Quasi Mont Carlo method can evaluate the rendering equation in real-time.udThe method can realize real-time walk-through of a complex virtual environment that has a mixtureudof diffuse and glossy reflection, computing multiple indirect bounces on the fly. We show that our methodudis capable of simulating fully dynamic environments including changes of view, materials, lighting andudobjects at interactive rates on commodity level graphics hardware.