Getting Rid of Links in Hierarchical Radiosity

Hierarchical radiosity with clustering has positioned itself as one of the most efficient algorithms for computing global illumination in non-trivial environments. However, using hierarchical radiosity for complex scenes is still problematic due to the necessity of storing a large number of transport coefficients between surfaces in the form of links. In this paper, we eliminate the need for storage of links through the use of a modified shooting method for solving the radiosity equation. By distributing only unshot radiosity in each step of the iteration, the number of links decreases exponentially. Recomputing these links instead of storing them increases computation time, but reduces memory consumption dramatically. Caching may be used to reduce the time overhead. We analyze the error behavior of the new algorithm in comparison with the normal gathering approach for hierarchical radiosity. In particular, we consider the relation between the global error of a hierarchical radiosity solution and the local error threshold for each link.