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

• Published in: Computer graphics forum Vol. 34; no. 2; pp. 575 - 584
• Main Authors: Simon, Florian, Hanika, Johannes, Dachsbacher, Carsten
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.05.2015
• Subjects: Analysis; Categories and Subject Descriptors (according to ACM CCS); Complement; Computation; Computer graphics; Glossy; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism-Raytracing; Illumination; Image processing systems; Light; Light sources; Placement; Radiance; Studies; Transport
• ISSN: 0167-7055; 1467-8659
• DOI: 10.1111/cgf.12585

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.