Abstract

Shadowing effects dramatically enhance the realism of virtual environments by providing useful visual cues. Shadow mapping is efficient and general applicable for real-time applications, but suffers from the inherent aliasing errors due to the image-based nature. We present the Parallel-Split Shadow Maps (PSSMs) scheme, which splits the view frustum into different parts and then generates multiple smaller shadow maps for the split parts. A fast and robust split strategy based on the analysis of shadow map aliasing is proposed, which produces a moderate aliasing distribution over the whole depth range. By applying the geometry approximation to the split parts instead of the whole scene, the tighter bounding shapes of visible objects enhance the utilization of shadow maps. Our system utilizes hardware acceleration for the extra rendering passes when synthesizing the scene shadows.

Our approach is intuitive without using complex data structures and supports real-time performance for large-scale and dynamic virtual environments. We further work on generalized perspective reparameterization in shadow mapping to reduce perspective aliasing errors and keep the linear perspective aliasing distribution in general cases, while the light and viewing directions are not orthogonal in dynamic virtual environments.