Simplifications used by most real time computer graphics systems:
Most computer graphic rendering systems only attempt to model the direct illumination from the emitters to the reflectors of the scene. On the other hand most systems ignore the geometry of light emitters, and consider only the geometry of reflectors. The rationalization behind these simplifications is that most of the light from a scene results from a single bounce of a emitted ray off of a reflective surface. This is, however, a very questionable assumption. In most computer generated pictures you will not see light directly emitted from the light source, nor the indirect illumination from a light reflecting off on surface and illuminating another. |
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Things forgotten or oversimplified here |
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First we will consider some very simple lighting models.