A Closed-Form Model for Image-Based Distant Lighting
This provides a faster and more accurate method for computer graphics rendering, though it appears incremental as it builds on existing mathematical foundations.
The paper tackles the problem of image-based lighting by deriving a closed-form solution to the light integral equation for distant environment illumination, resulting in noise-free rendering and an order of magnitude or higher speedup compared to Monte Carlo and spherical harmonics methods.
In this paper, we present a new mathematical foundation for image-based lighting. Using a simple manipulation of the local coordinate system, we derive a closed-form solution to the light integral equation under distant environment illumination. We derive our solution for different BRDF's such as lambertian and Phong-like. The method is free of noise, and provides the possibility of using the full spectrum of frequencies captured by images taken from the environment. This allows for the color of the rendered object to be toned according to the color of the light in the environment. Experimental results also show that one can gain an order of magnitude or higher in rendering time compared to Monte Carlo quadrature methods and spherical harmonics.