## Partitioning and Ordering Large Radiosity Computations

Seth Teller,
Celeste Fowler
Tom Funkhouser, and
Pat Hanrahan.
Proceedings of SIGGRAPH 1994

### Abstract

We describe a system that computes radiosity solutions for polygonal
environments much larger than can be stored in main memory. The solution
is stored in and retrieved from a database as the computation proceeds.
Our system is based on two ideas: the use of visibility oracles to find
source and blocker surfaces potentially visible to a reveiving surface; and
the use of hierarchical techniques to represent interactions between
large surfaces efficiently, and to represent the computed radiosity solution
compactly. Visibility information allows the environment to be
*partitioned* into subsets, each containing all the information necessary
to transfer light to a cluster of receiving polygons. Since the largest
subset needed for any particular cluster is much smaller than the total
size of the environment, these subset computations can be performed
in much less memory than can classical or hierarchical radiosit. The
computation is then *ordered* for further efficiency. Careful ordering
of energy transfers minimizes the number of database reads and writes. We
report results from large solutions of unfurnished and furnished buildings, and
show that our implementation's observed running time scales nearly linearly
with both local and global model complexity.
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