Layered occlusion map for soft shadow generation

Abstract

This paper presents a high-quality high-performance algorithm to compute plausible soft shadows for complex dynamic scenes. Given a rectangular light source, the scene is rendered from the viewpoint placed at the center of the light source, and discretized into a layered depth map. For each scene point sampled in the depth map, the occlusion degree is computed, and stored in a layered occlusion map. When the scene is rendered from the camera's viewpoint, the occlusion degree of a scene point is computed by filtering the layered occlusion map. The proposed algorithm produces soft shadows the quality of which is quite close to that of the ground truth reference. As it runs very fast, a scene with a million polygons can be rendered in real-time. The proposed method does not require pre-processing and is easy to implement in contemporary graphic hardware.