Hierarchical Radiosity for Dynamic Environments

This paper extends the hierarchical radiosity method to environments in which geometry and surface attributes can be changed dynamically. New algorithms are presented for maintaining an appropriately-sized mesh and speeding the construction of the corresponding linear system. Mesh folding, the unrefinement of a mesh, is used to optimize mesh size while maintaining a specified error tolerance. Two new interactions are introduced: shadow links guide local shadow clean up after a change in geometry and ghost links guide global mesh folding after a change in surface attributes. The algorithms stabilize the memory requirements of dynamic scenes. Different types of interactions are analyzed to determine how they are affected by changes in geometry. A dynamic scene-partitioning scheme called a motion volume, used in conjunction with a three-dimensional clipping algorithm, provides a fast way to cull interactions that do not need to be updated. The algorithms are demonstrated on several sample scenes.