Radiosity Computations Research Articles

Automatic Creation of Object Hierarchies for Radiosity Clustering

Using object clusters for hierarchical radiosity greatly improves the efficiency and thus usability of radiosity computations. By eliminating the quadratic starting phase very large scenes containing about 100k polygons can be handled efficiently. Although the main algorithm extends rather easily to using object clusters, the creation of ‘good’ object hierarchies is a difficult task both in terms of construction time and in the way how surfaces or objects are grouped to clusters. The quality of an object hierarchy for clustering depends on its ability to accurately simulate the hierarchy of the energy flow in a given scene. Additionally it should support visibility computations by providing efficient ray acceleration techniques.In this paper we will present a new approach of building hierarchies of object clusters. Our hybrid structuring algorithm provides accuracy and speed by combining a highly optimized bounding volume hierarchy together with uniform spatial subdivisions for nodes with regular object densities. The algorithm works without user intervention and is well suited for a wide variety of scenes. First results of using these hierarchies in a radiosity clustering environment are very promising and will be presented here.The combination of very deep hierarchies (we use a binary tree) together with an efficient ray acceleration structure shifts the computational effort away from form factor and visibility calculation towards accurately propagating the energy through the hierarchy. We will show how an efficient single pass gathering can be used to minimize traversal costs.

Partitioning and Scheduling Large Radiosity Computations in Parallel

We show, in this paper, how it is feasible to efficiently perform large radiosity computations on a conventional (distributed) shared memory multiprocessor machine. Hierarchical radiosity algorithms, although computationally expensive, are an efficient view-independent way to compute the global illumination which gives the visual ambiance to a scene. Their effective parallelization is made challenging, however, by their non-uniform, dynamically changing characteristics, and their need for long-range communication. To address this need, we have developed appropriate partitioning and scheduling techniques, that deliver an optimal load balancing, while still exhibiting excellent data locality. We provide the detailed implementation of these techniques and present results of experiments showing very good acceleration and scalability performances. The accurate radiosity solutions required to render high quality images of an extremely large model are computed in a reasonable time. The rendering capabilities of modern graphics hardware are then used to visualize this virtual pre-lit environment in real-time: a two minutes QuickTime movie example can be downloaded from our site: ftp://ftp.loria.fr/pub/loria/isa/Cavin/sodaHallWalk.qt.gz (last accessable in 2000)

Visibility masks for solving complex radiosity computations on multiprocessors

This paper presents a strategy to handle very complex scenes for radiosity computation. Compared to other radiosity algorithms, our solution focuses on the ability to compute the radiosity in local environments instead of solving the problem for the whole environment. By splitting the problem into subproblems, using virtual interface and visibility masks, our technique is able to achieve better data locality than other standard solutions. We present an implementation of visibility masks on a distributed memory parallel computer (Intel Paragon XP/S).