At 12:07 AM 8/28/2003, asimovd@aol.com wrote:
Light sources are usually modeled as point sources, which works fairly well. Another reasonable simplification that's used is the light source is assumed to be "at infinity" so that its rays are emitted all parallel to each other, making angle calculations easier.
Make any simplifying assumptions necessary, like making the Sun a point, very far away. (I didn't mean for the size of the sun to enter into it.)
(The moon is often given as an example of a pure diffuse reflection -- as you look at the lunar disk of a full moon, the reflected light is virtually independent of whether you look, from the the center of the disk to right near its edge.)
Yes, I think that's what I meant by the second version.