Papers
Real-time Editing and Relighting of Homogeneous Translucent Materials. The Visual Computer Journal, Proceedings of Computer Graphics International 2008. To appear.
Rui Wang, Ewen Cheslack-Postava, Rui Wang, David Luebke, Qianyong Chen, Wei Hua, Qunsheng Peng, and Hujun Bao.
Existing techniques for fast, high-quality rendering of translucent materials often fix BSSRDF parameters at precomputation time. We present a novel method for accurate rendering and relighting of translucent materials that also enables real-time editing and manipulation of homogeneous diffuse BSSRDFs. We first apply PCA analysis on diffuse multiple scattering to derive a compact basis set, consisting of only twelve 1D functions. We discovered that this small basis set is accurate enough to approximate a general diffuse scattering profile. For each basis, we then precompute light transport data representing the translucent transfer from a set of local illumination samples to each rendered vertex. This local transfer model allows our system to integrate a variety of lighting models in a single framework, including environment lighting, local area lights, and point lights. To reduce the PRT data size, we compress both the illumination and spatial dimensions using efficient nonlinear wavelets. To edit material properties in real-time, a user-defined diffuse BSSRDF is dynamically projected onto our precomputed basis set, and is then multiplied with the translucent transfer information on the fly. Using our system, we demonstrate realistic, real-time translucent material editing and relighting effects under a variety of complex, dynamic lighting scenarios.
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4D Compression and Relighting with High-Resolution Light Transport Matrices. Proceedings of ACM Symposium on Interactive 3D Graphics, 2007.
Ewen Cheslack-Postava, Nolan Goodnight, Ren Ng, Ravi Ramamoorthi and Greg Humphreys.
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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We present a novel 3D scanning system with the potential for interactive acquisition and visualization of dynamic scenes. Our system uses a spatio-temporally adaptive sampling strategy, and can take advantage of multiple simultaneous scanning devices operating at different resolutions. We also employ a level set framework for reconstructing potentially dynamic scenes from multiple concurrent streams of range data. In our framework, implicit surfaces are reconstructed periodically from new samples on a course grid, creating a sequence of reconstructions from disjoint sample sets that is used to estimate motion in the scene. A high-resolution reconstruction proceeds alongside, where the surface is evolved by a convective flow that guides it towards the sample set. We employ a spatially-varying distance metric based on our motion estimate that adaptively constrols the contribution of older samples to the final reconstruction.