Andrew J. Willmott

Hierarchical Radiosity with Multiresolution Meshes Degree Type: Ph.D. in Computer Science
Advisor(s): Paul Heckbert
Graduated: December 2000

Abstract:

The hierarchical radiosity algorithm solves for the global transfer of diffuse illumination in a scene. While its potential algorithmic complexity is superior to both previous radiosity methods and distributed ray tracing, for scenes containing detailed polygonal models, or highly tessellated curved surfaces, its time performance and memory consumption are less than ideal.

My thesis is that by using hierarchies similar to those of multiresolution models, the performance of the hierarchical radiosity algorithm can be made sub-linear in the number of input polygons, and thus make radiosity on scenes containing detailed models tractable. The underlying goal of my thesis work has been to make high-speed radiosity solutions possible with such scenes.

To achieve this goal, a new face clustering technique for automatically partitioning polygonal models has been developed. The face clusters produced group adjacent triangles with similar normal vectors. They are used during radiosity solution to represent the light reflected by a complex object at multiple levels of detail. Also, the radiosity method is reformulated in terms of vector irradiance. Together, face clustering and the vector formulation of radiosity permit large savings. Excessively fine levels of detail are not accessed by the algorithm during the bulk of the solution phase, greatly reducing its memory requirements relative to previous methods. Consequently, the costliest steps in the simulation can be made sub-linear in scene complexity. I have developed a radiosity system incorporating these ideas, and shown that its performance is far superior to existing hierarchical radiosity algorithms, in the domain of scenes containing complex models.

Thesis Committee:
Paul Heckbert (Chair)
David O’Hallaron
Steven Seitz
François Sillion

Randy Bryant, Head, Computer Science Department
James Morris, Dean, School of Computer Science

Keywords:
Global illumination, hierarchical radiosity, face cluster hierarchies, multiresolution models