At 08:08 PM 10/24/00 -0400, Tim May wrote:
Nonsense, on at least a couple of accounts. I was active in the image processing field in 1980-84, and attended various SIGGRAPHs and suchlike. Fact is, "ray tracing" and various illumination models, and Gouraud and Phong shading and all the rest...were NOT motivated by a desire to model "*physics*." Physicist didn't give a dang about modelling light sources in 3D environments, and about morphing and wrapping and all that.
Not *that* kind of physicist. Something more like psychophysics (ie measurement of human perception) empowered by these newfangled computer thangs. There was a desire to see what was sufficient to generate photorealism. After all, the shading models you mention are crude approximations; but they usually work[1], which talks to the limits of perception. And to a nontrivial physics of a certain scale (modelling translucent objects, objects with embedded reflectors and adsorbers, etc.) There was also a desire to understand the rendering process so that you could understand the *inverse*, ie, inferring the world from what you see. Machine vision. Rendered jello, fires, fractal cloud effects, realistic water, rocks, etc. Hollywood was for a while making entire movies around a single new model (particle systems in that terraforming star trek movie). The question that motivates was, how do you do that? Where 'that' might be rendering hair, or modelling how skin creases at elbows. I modelled wood grain with a VAX in 1985 using a 24 bit monitor that cost more than some cars. Nowadays you would just scan and texture map real wood, but the (psychophysical) question was, what did you need to model to get grain indistinguishable from real[2]? Texture mapping is cheating. Similar questions exist for modelling motion. How many harmonics do you need to render for realistic motion? How do you make a desklamp move with emotion? (Luxo Jr..) (Recording actors and mapping movement is cheating, Mr. Spielberg.)
The motivation was to produce special effects for education films (a la James Blinn at JPL), effects for movies (a la Alvy Ray Smith, eventually of Pixar), and advertisements for Hollywood and Madison Avenue.
These folks had a more academic interest than you make out.. Blinn wrote a very mathematical column.. the sci films and movies paid the bills, bought the equiptment, etc., and sometimes motivated problems, but the problems were fascinating in and of themselves. Sure, their output was often visual candy, but it was new and interesting regardless of jazz appeal. [1] The moon does not show the cos(incidence-angle) reflectance of typical matte surfaces, and thus looks flat. Its surface is powder. [2] slice vertical concentric shells with radially varying albedo (annual rings) paired with small vertical radial planes (rays). The 3D geometry yields 2D constraints on the texture that distinguish it from other striated textures. Turning the knobs generates different types of woodgrains.