ABSTRACT
This chapter presents a technique for generating soft shadows based on shadow maps and screen space image filtering. The main idea is to use a mipmap to represent multifrequency shadows in screen space. The mipmap has two channels: the first channel stores the shadow intensity values and the second channel stores screen-space penumbrae widths. Shadow values are obtained by filtering while penumbrae widths are propagated by flood filling. After the mipmap is generated, the penumbrae values are used as indices to the mipmap levels. Thus, we transform the problem of shadow generation into the problem of selecting levels in a mipmap. This approach is extended by including layered shadow maps to improve shadows with multiple occlusions.
