MIT Department of Electrical Engineering & Computer Science

MIT EECS
1994 (Fall Semester)
Colloquium Series

Monday, November 28, 1994

LIGHTING SIMULATION FOR LARGE ENVIRONMENTS

Seth Teller
Massachussets Institute of Technology
Department of Electrical Engineering and Computer Science

We describe a system that computes radiosity solutions for polygonal environments much larger than can be stored in main memory. The input to the system is a collection of colored, diffusely emitting and/or reflecting surfaces. The output is a discretization of the surfaces, along with illumination information about each surface element.

Our system is novel in that it _partitions_ and _orders_ the solution computation in order to accomplish it in a small amount of physical memory, while incurring only small I/O overhead. The implementated system reduces physical memory requirements by nearly three orders of magnitude, in comparison to existing implementations.

The solution is stored in and retrieved from a _spatial database_ as the computation proceeds. Visibility modules find the source and blocker surfaces potentially visible to each receiving surface. Hierarchical techniques represent interactions between large surfaces efficiently, and represent the computed radiosity solution compactly. The computation is _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 previous algorithms required. The subset computations are then _ordered_ to minimize 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.

(Joint work with Celeste Fowler, Thomas Funkhouser, and Pat Hanrahan.)

November 28, 1994
4-5pm
Grier Room (34-401)
Refrehment at 3:30 pm