4D compression and relighting with high-resolution light transport matrices
This paper presents a method for efficient compression and relighting with high-resolution, precomputed light transport matrices. We accomplish this using a 4D wavelet transform, transforming the columns of the transport matrix, in addition to the 2D row transform used in previous work. We show that a standard 4D wavelet transform can actually inflate portions of the matrix, because high-frequency lights lead to high-frequency images that cannot easily be compressed. Therefore, we present an adaptive 4D wavelet transform that terminates at a level that avoids inflation and maximizes sparsity in the matrix data. Finally, we present an algorithm for fast relighting from adaptively compressed transport matrices. Combined with a GPU-based precomputation pipeline, this results in an image and geometry relighting system that performs significantly better than 2D compression techniques, on average 2x-3x better in terms of storage cost and rendering speed for equal quality matrices.
Ewen Cheslack-Postava, Nolan Goodnight, Ren Ng, Ravi Ramamoorthi, and Greg Humphreys. "4D compression and relighting with high-resolution light transport matrices". In proceedings of the 2007 symposium on Interactive 3D graphics and games, pages 81–88, 2007.