ABSTRACT
This chapter describes a percentage-closer filtering (PCF) based extension to an adaptive shadow maps (ASM) algorithm. ASM is a method that addresses perspective and projection aliasing that occurs in standard shadow mapping. Another notable advantage of ASM is the ability to exploit frame-to-frame coherency, which was the main reason for implementing the method in Funcom’s Age of Conan. Provided that granularity of the scene is reasonably fine and there is a certain frame-to-frame coherency, ASM significantly reduces shadow map rendering costs compared to standard shadow mapping. A fundamental shortcoming of ASM is its inability to handle animated objects because such objects require updating the shadow map with every frame, while ASM relies on a shadow maps cache that holds data created over many frames. Implementing ASM-based soft shadows provided not only a substantial increase in image quality, but also a significant performance boost.
