Efficient from-point visibility for global illumination in virtual scenes with participating media

Více o knize

Visibility determination is crucial for photorealistic image synthesis, as the light reflected at a shading point relies on visible scene surfaces and light sources. However, computing visibility is computationally intensive, with global illumination algorithms like final gathering and bias compensation consuming significant rendering time. This thesis aims to enhance the performance of these algorithms by proposing efficient methods for computing and storing visibility, while utilizing feasible visibility approximations that minimize artifacts. We explore a (hemi-)spherical parameterization based on the octahedron for effective visibility storage at arbitrary shading points. Building on this, we develop a point-based rendering technique that computes (hemi-)spherical visibility for final gathering. We leverage epipolar geometry to exploit visibility coherence and derive an optimized screen-space sampling strategy for single scattering from point light sources in homogeneous media. By combining single scattering from multiple (virtual) point light sources, we can approximate global illumination with multiple scattering using instant radiosity and bias compensation. Bias compensation addresses illumination errors caused by energy elimination over short distances, but it is computationally demanding due to the numerous visibility evaluations required. To enhance efficiency, we propose various visibility approximations in partici