Rich-VPLs for Improving the Versatility of Many-Light Methods

Florian Simon, Johannes Hanika, and Carsten Dachsbacher

Computer Graphics Forum (Proceedings of Eurographics 2015)

The Disco-scene with multiple colored light sources and reflected highly-glossy caustics where colors add to whitish light. Rendered with our new virtual light type “Rich-VPL” (left), standard VPLs (middle left), virtual spherical lights (VSL, middle right), and path tracing reference (right). All many-light methods use 25k virtual lights; our method introduces an overhead of about 50% (less in more complex scenes) on top of standard VPL rendering, but significantly improves the ability to capture glossy and near-specular light transport. VSL require about 20% additional rendering time on top of standard VPLs due to stochastic sampling.
Many-light methods approximate the light transport in a scene by computing the direct illumination from many virtual point light sources (VPLs), and render low-noise images covering a wide range of performance and quality goals. However, they are very inefficient at representing glossy light transport. This is because a VPL on a glossy surface illuminates a small fraction of the scene only, and a tremendous number of VPLs might be necessary to render acceptable images. In this paper, we introduce Rich-VPLs which, in contrast to standard VPLs, represent a multitude of light paths and thus have a more widespread emission profile on glossy surfaces and in scenes with multiple primary light sources. By this, a single Rich-VPL contributes to larger portions of a scene with negligible additional shading cost. Our second contribution is a placement strategy for (Rich-)VPLs proportional to sensor importance times radiance. Although both Rich-VPLs and improved placement can be used individually, they complement each other ideally and share interim computation. Furthermore, both complement existing many-light methods, e.g. Lightcuts or the Virtual Spherical Lights method, and can improve their efficiency as well as their application for scenes with glossy materials and many primary light sources.




Slides (PDF)

Slides (Keynote)
  title = {Rich-VPLs for Improving the Versatility of Many-Light Methods},
  author = {Florian Simon and Johannes Hanika and Carsten Dachsbacher},
  year = 2015,
  volume = 34,
  number = 2,
  journal = {Computer Graphics Forum (Proceedings of Eurographics)},
  month = {May},
  pages = {575--584}