Nathan Kopp wrote:
> 
> Xplo Eristotle <inq### [at] unforgettablecom> wrote...
> > Seems to me that the higher an object's reflection is, the less its
> > pigment should have any effect on its appearance (provided that you're
> > using non-metallic reflection), until you reach reflection 1, at which
> > point the pigment would cease to be relevant.
> 
> Actually, diffuse, phong, and specular (and blinn in MegaPov) model
> first-order reflections (light that comes directly from light sources, hits
> the object, and is reflected to the camera).   The "reflection" property, on
> the other hand, models higher order reflections (light that hits one object,
> is reflected, hits the second object (and possible more), then hits the
> camera).
> 
> Because they model different phenomenons, you can't create a give/take
> relationship between them as you suggest.

I've given this some more thought (and if you've studied this for years
and I'm missing some vital piece of information that causes me to spout
uneducated nonsense, forgive me), and I don't see why this is true.

Light is light, whether it comes from the sun, a light bulb, a firefly,
or bouncing off of other objects. The frequencies and intensity vary,
but the behavior is essentially the same. When light hits a
non-reflective object, what's really happening is that the light is
being reflected in a zillion random directions (which also holds for
light that radiates off of other objects; in this sense, you could say
that illumination from radiosity is actually "diffuse reflection"). But
when light hits a reflective object, the light bounces off in some
uniform direction (or, if it hits a curved surface, according to some
uniform angle-of-incidence formula).. which means that when you shoot
light at a reflective object, it should bounce off such that less of it
actually reaches the viewer. A totally reflective sphere, existing
within a space which is totally black except for a point light, should
appear as a tiny dot (where the light reflects towards the viewer.. and
even that dot would be so small as to be nearly invisible, but in the
real world, nothing is PERFECTLY reflective, and you'd probably perceive
a tiny glare halo in addition to the teensy-tiny highlight).

Of course, raytracers don't shoot light, they shoot imaginary camera
rays. But it seems to me that an optional diffuse/reflected light
tradeoff is an improvement over not having one, even if it's not
perfectly accurate (in the real world, a reflective object would reflect
radiosity as though it were photons, and I don't know whether the
current photon implementation provides for this, or indeed COULD provide
for this). And as I've pointed out, you can hack the numbers to produce
this effect for uniform reflection, but there's presently no way to make
variable reflection conform properly.. which is why I think one is needed.

-- 
Xplo Eristotle
http://start.at/xplosion/

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