A Shadow-Volume Algorithm for Opaque and Transparent Nonmanifold Casters

Since precise shadows can be generated in real time, graphics applications often use the shadow-volume algorithm. This algorithm was limited to manifold casters but has been recently extended to general nonmanifold casters with oriented triangles. We provide a further extension to general nonmanifold meshes and an additional extension to shadows of transparent casters. To achieve these, we first introduce a generalization of an object's silhouette to nonmanifold meshes. By using this generalization, we can compute the number of caster surfaces between the light and receiver, and furthermore, we can compute the light intensity arriving at the receiver fragments after the light has traveled through multiple colored transparent receiver surfaces. By using these extensions, shadows can be generated from transparent casters that have constant color and opacity.