An object-oriented shadow generation algorithm for real-time application

Presents a fast shadow generation algorithm for a large number of convex polyhedra (objects) in a 3D scene based on the concept of characteristic views (CVs). The concept of CVs is that the infinite possible views of a 3D polyhedron can be grouped into a finite number of classes which have the same visible polygons from some reference points (i.e. viewpoints or point light sources). The space can be partitioned into subspaces in which all reference points have the same object ordering. Basically, object-precision hidden surface removal algorithms and object-precision shadow generation algorithms are the same except for the reference point. The shadow volume binary space partitioning (SVBSP) tree algorithm is known to be efficient in a static environment in which the point light source can be changed. However, if a scene consists of many objects and each object consists of many polygons, the time complexity for generating and traversing the SVBSP tree increases rapidly because the SVBSP tree algorithm deals with polygons which are components of objects. Furthermore, the SYBSP tree algorithm suffers from polygon-splitting problems resulting in a high cost as the number of polygons increases. Our approach is object-oriented in the sense that an object is used as the basic unit and polygons can be considered as components of the associated object. For all light source positions, the object ordering for shadow generation is determined at the preprocessing stage. At run-time, the shadow detection algorithm is executed and, if necessary, shadow fragments are generated