4D Compression and Relighting with High-Resolution Light Transport Matrices

Ewen Cheslack-Postava1, Nolan Goodnight2, Ren Ng3, Ravi Ramamoorthi4, and Greg Humphreys5

1 Stanford University
2 NVIDIA
3 Refocus Imaging
4 Columbia University
5 University of Virginia

To appear at I3D 2007

Abstract

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.

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