# Radiosity Calculations for Rotational Surfaces

Helmut Mastal, Robert F. Tobler, Werner Purgathofer

Institute of Computer Graphics, Vienna University of Technology,

A-1040 Karlsplatz 13/186/2
## Abstract

Rotational Surfaces are very important for photorealistic representations of
plants and other natural phenomena. In this paper radiosity calculations for
rotational surfaces are presented that handle surfaces as whole objects
rather than approximating them by large numbers of plane patches. Mathematical
expressions are given for the radiance of cylinders, cones and spheres that
are ideal Lambertian reflectors.

Although there exists no complete radiosity algorithm which uses the formulae
for cylinders, cones and spheres at the moment, it can be estimated that the
number of objects of a global illumination scene as well as the number of
interactions could be reduced dramatically. Therefore it should be possible
to render more complex scenes with plants, like forests, in reasonable time.
## Keywords

radiosity, rotational surfaces, natural phenomena