Real-time Indirect Illumination with Clustered Visibility
Zhao Dong, Thorsten Grosch, Tobias Ritschel, Jan Kautz, Hans‐Peter Seidel · 2009
Figure 1: One-bounce diffuse global illumination rendered at 800×800 pixels for a scene with dynamic geometry (17 k faces) and dynamic lighting at 19.7 fps. Our method uses soft shadows from 30 area lights to efficiently compute the indirect visibility. Visibility computation is often the bottleneck when rendering indirect illumination. However, recent methods based on instant radiosity have demonstrated that accurate visibility is not required for indirect illumination. To exploit this insight, we cluster a large number of virtual point lights – which represent the indirect illumination when using instant radiosity – into a small number of virtual area lights. This allows us to compute visibility using recent real-time soft shadow algorithms. Such approximate and fractional from-area visibility is faster to compute and avoids banding when compared to exact binary from-point visibility. Our results show, that the perceptual error of this approximation is negligible and that we achieve real-time frame-rates for large and dynamic scenes. 1