Evaluation of Performance and Image Quality for Voxel Cone Tracing

Abstract: Voxel cone tracing (VCT) is a rendering method designed to approximate global illumination in a fast and efficient way. Global illumination means to render not only the direct lighting of a scene but also light from indirect sources, simulating how light in the real-world tend to bounce around and illuminate even the areas that are occluded from a direct light source. Rendering accurate global illumination in real-time has for a long time been a challenge in the field of computer graphics. This effect is most accurately simulated through expensive algorithms such as path tracing, where individual rays of light are traced from the pixels of a camera as they bounce around the scene and sample the environment. More efficient methods tend to rely on static image-based approaches, where global illumination is pre-rendered and baked into textures. VCT presents itself as a middle ground of the two, trading some of the accuracy for improved performance and the ability to work in a fully dynamic environment where objects and light sources may be moved around. VCT computes global illumination by volumetrically sampling a lower resolution voxel-based representation of the rendered scene by tracing cones.   The aim of this thesis is to further investigate the performance and image quality of VCT through an implementation and evaluation method. A VCT algorithm has been implemented that is capable of real-time global illumination in a dynamic setting, utilizing physically based rendering for improved image quality and a sparse 3D texture for efficient voxel storage. Performance was then measured in terms of rendering speed and memory usage. Image quality was evaluated through comparison with accurate path traced reference images. The results show that VCT is a promising rendering method for achieving a real-time approximation of global illumination, but that it also suffers from some issues regarding the image quality.