View-Dependent Precomputed Light Transport Using Nonlinear Gaussian Function Approximations


Paul Green Jan Kautz Wojciech Matusik Fredo Durand
I3D 2006


Rendering of the Armadillo model (a) with 50K vertices and the Dane model (b) with 15K vertices. Full rendering frame rate for Armadillo is 10Hz. Dane renders at 40Hz. Both models are rendered using a single Gaussian lobe for the view-dependent component, and fifth-order spherical harmonics for the diffuse component.




We propose a real-time method for rendering rigid objects with complex view-dependent effects under distant all-frequency lighting. Existing precomputed light transport approaches can render rich global illumination effects, but high-frequency view-dependent effects such as sharp highlights remain a challenge. We introduce a new representation of the light transport operator based on sums of Gaussians. The nonlinear parameters of our representation enable 1) arbitrary bandwidth because scale is encoded as a direct parameter, and 2) high-quality interpolation across view and mesh triangles because we interpolate the mean direction of the Gaussians, thereby preventing linear cross-fading artifacts. However, fitting the precomputed light transport data to this new representation requires solving a nonlinear regression problem that is more involved than traditional linear and nonlinear (truncation) approximation techniques. We present a new data fitting method based on optimization that includes energy terms aimed at enforcing artifact-free interpolation. We demonstrate that our method achieves high visual quality with a small storage cost and an efficient rendering algorithm.



Paul Green, Jan Kautz, Wojciech Matusik, and Fredo Durand. View-Dependent Precomputed Light Transport Using Nonlinear Gaussian Function Approximations. ACM Symposium in Interactive 3D Graphics and Games 2006.