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.