The (Adapted Cornell Box, Courtesy of the 3D Studio Advanced Lighting Examples (See Program Data/3DSmax3_1/Scenes)

This tutorial demonstrates the differences between Computer Graphics Rendering and Global Illumination. It is provided as information support to the lecture on the same topic.

Computer Graphics

This set of tutorials uses a small room originally described by Cindy M. Goral, Kenneth E. Torrance, and Donald P. Greenberg for their 1984 paper Modeling the interaction of Light Between Diffuse Surfaces, Computer Graphics (SIGGRAPH '84 Proceedings), Vol. 18, No. 3, July 1984, pp. 213-222. A more recent version is shown in the picture above. The room geometry I have used is provided in one of the sample files accompanying 3D Studio Max. The initial computer graphics renderings are from Max, but the techniques and language used are applicable to most rendering programs used today. The original purpose of the red and blue walls was to highlight the colour bleed between surfaces that radiosity type lighting calculations will promote.

The principal difference between the Cornell room and the one used here is the presence of two spheres - one chrome and one glass, rather than the cuboid shapes used in the Cornell box. These allow another related aspect of the computer graphic artist's bag of tricks to be explored: materiality as revealed by a surface's interaction with light.

In the "advanced lighting" demo file from 3DS Max as illustrated above, there are four light sources:

1. a spot light placed where the light box is on the ceiling aimed at the centre of the glass sphere in the left foreground
2. a point light illuminating evenly in all directions alongside the spot light
3. a point light with a limited radius fall off in intensity that is red in colour near the left hand red wall
4. a point light with a limited radius fall off in intensity that is blue in colour near the right hand blue wall

The goal of the 3DS max file is to demonstrate how the red and blue lights can give the illusion of radiosity - without the computational overhead. With the aid of blur and careful manipulation of the width of the spotlight beam, the caustics resulting from the interaction of the glass sphere and the spot light are also faked...

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