ABSTRACT
This chapter describes a technique to provide soft shadows using a single texture sample in environments where the objects casting shadows and the objects receiving shadows are disjoint. A gobo is a theatrical term that refers to a cutout shape that can be placed in front of a spotlight light bulb. When the spotlight is turned on, the gobo cutout will partially block some light and the resultant shape will be projected onto the scene. The main problem with basic gobo shadowing, especially for infinitely far directional shadowing such as from the sun, is that it is often impossible to guarantee that there is no surface between the light source and the gobo-casting object. This will lead to the gobo incorrectly projecting onto closer ob jects that should be fully in light.
