Interactive relighting with dynamic BRDFs

Xin Sun, Kun Zhou, Yanyun Chen, Stephen Lin, Jiaoying Shi, Baining Guo
2007 ACM Transactions on Graphics  
Figure 1: Image sequence of Venus rendered with a dynamic BRDF. Ground truth renderings of the corresponding materials are shown on spheres at the bottom-right of the images. The changes in Venus' reflectance properties produce corresponding indirect lighting effects on the surrounding walls. Here, precomputation of 12.3 hours with 389 Mbytes memory is used for the 39.7K vertices. The rendering performance is 2.62 fps when the viewpoint, BRDF, and lighting are all simultaneously changing; 10.94
more » ... fps when only the viewpoint and BRDF are dynamic; and 57.09 fps when only the viewpoint changes. Abstract We present a technique for interactive relighting in which source radiance, viewing direction, and BRDFs can all be changed on the fly. In handling dynamic BRDFs, our method efficiently accounts for the effects of BRDF modification on the reflectance and incident radiance at a surface point. For reflectance, we develop a BRDF tensor representation that can be factorized into adjustable terms for lighting, viewing, and BRDF parameters. For incident radiance, there exists a non-linear relationship between indirect lighting and BRDFs in a scene, which makes linear light transport frameworks such as PRT unsuitable. To overcome this problem, we introduce precomputed transfer tensors (PTTs) which decompose indirect lighting into precomputable components that are each a function of BRDFs in the scene, and can be rapidly combined at run time to correctly determine incident radiance. We additionally describe a method for efficient handling of high-frequency specular reflections by separating them from the BRDF tensor representation and processing them using precomputed visibility information. With relighting based on PTTs, interactive performance with indirect lighting is demonstrated in applications to BRDF animation and material tuning.
doi:10.1145/1239451.1239478 fatcat:o57yt63rcfdsnpcqkgzsgbvemi