Multiple strategy stochastic iteration for architectural walkthroughs
Architectural walkthroughs require fast rendering algorithms and also physically accurate results. This paper introduces a global illumination method that combines several strategies to meet these contradicting criteria. The methods include parallel and perspective ray-bundle shooting and ray shooting. Each method is designed to randomly approximate the effect of the light transport operator. Parallel ray-bundle tracing transfers the radiance of all points parallel to a randomly selected global direction, with perspective ray-bundles we can shoot the radiance of a single patch in all directions, and ray shooting transfers the radiance of a randomly selected point at a randomly selected direction. These strategies have complementary features since each of them is effective in different illumination conditions. In each step of the proposed iterative algorithm the applied strategy is selected randomly according to the properties of the current radiance distribution. The formal framework of the combination is the stochastic iteration. Although the algorithm is view dependent, a rough approximation of the radiance function is stored in object-space, which allows fast animations at reasonable storage requirements and also speeds up Monte-Carlo simulations. The method is also suited for interactive walkthrough animation in glossy scenes since when the viewpoint changes, the object-space radiance values remain valid and the image quickly adapts to the new situation.
stochastic iteration global illumination finite-element techniques monte-carlo methods