Everyone was so great in replying to my previous question, that I'd
like to post this topic. If this was an essay question, I would phrase
it so: To what extent does Povray simulate reality and to what extent
are its images simply illusions? The point is that to allow the user to
create all sorts of images, Povray gives incredible control over
reality. Consider shadowless objects. Or, say I want to make a scene
with a mirror that doesn't reflect a vampire. In reality, mirrors
reflect and there are no vampires, but that can be changed in Povray.
You can make a ceiling out of water, or a seemingly impossible m.c.
echer model, or abstract fractals, or whatever.
  It seems obvious. Of course Povray should allow you to do all those
things. The only thing that should be real is the light and its
behavior. But consider this. When I was starting, I wanted to simulate
the effect of an oil slick on water. So, I made two thin surfaces with
different indexes of refraction, hoping to get the effect. Boy, was I
surprised that the irridescence property can achieve the interference
effect on a single surface. In reality, that's impossible.
   So here are several technical problems I'm facing now. First, I want
to make a realistic looking CD. Now, it wouldn't be wise to make a disk
with millions of dents in it, would it. So what do I use to fool the
viewer? A rainbow, a halo, what? Or how about this: as you may know, if
you shine a strong, monochromatic, coherent light.right at a penny, you
should get a bright spot in the center of its shadow as a result of
light diffraction. I can certainly achieve the effect, but how much of
it would be attributed to properties of light? Or, how about Young's
double-slit experiments and light fringes, diffraction gratings, or
polarized light. And what about "materials" with unusual optical
properties. Gypsum, for example, is trasparent but it creates a double
image of anything viewed through it. How much can you assign and let
Povray take care of it, and how much do you have to take upon yourself
to model?

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