Stencil shadow volumes for complex and deformable objects

Abstract

We present a real-time shadow method based on the shadow volume that exploits capabilities of the modern graphics cards. The algorithm is primarily created for casting shadows of highly concave complex objects such as trees. For those objects, silhouette calculation that is usually preformed by other shadow volume algorithms is complicated and poorly justified. Instead of calculations, it is better to assume a worst case scenario and use all of the edges for construction of the shadow volume mesh, skipping silhouette determination entirely. The achieved benefit is that all procedures, i.e. the object and shadow calculation and rendering, could be done on GPU. The proposed solution for shadow casting allows open edges. Indexed vertex blending is used for shadow projections, and the only calculation required is determining projection matrices. Once created, shadow volume is treated like any other mesh.