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On an aside question:
Does anyone have the source for POV 3.1e, not 3.1a , for win95?
And now for the meat and potatos:
Along with the new radiosity, I'm going to add Fresnel reflectance to objects
that already contain reflection. That is, unless one of you wants to beat me
to it! The equation for fresnel reflectance based off regular reflection is
fresnel_reflection = reflection +
((1.0-(V dot R)) * (1.0-reflection))*amount
Where V is the vector coming out of the intersection point towards the
viewpoint (reversed traced ray) and R is the reflected vector. All are
normalized of course. "amount" is a number <= 1.0 and > 0.0 that says how
much the effect takes place. You'll need to add keyword "fresnel" as a toggle
and "amount" as a parameter in finish{} statements. If fresnel is on,
reflection should be merely replaced by the above equation. Viola.
(For you physicists, yes, this equation ignores the wavelength of the light.
I suppose this makes some "big difference" in some "laser laboratory"
somewhere.)
Fresnel reflection first caught my attention in a number of scenes from 3D
Studio Max. Some of the renders were amazingly realistic. It adds a gloss
to objects like nothing else I've ever seen. It some cases it even makes
objects look wet.
It basically follows the rule that the more shallow the angle of incidence,
the more reflected light takes over. If the light is reflected almost
directly back towards the eye then the less reflected light plays and the more
the diffuse or transmitted component takes over. If you've been in a
swimming pool once in your life you've already seen this effect.
Some real-life surfaces that actually have this are
-Water.
-Laminated wood.
-Car finishes.
- Anything glossy.
In general, glass and certain metals do not have this property. This is the
reason, if you've noticed, that water tends to look more like molten glass in
ray-traced scenes than photorealistic water. Have at it...
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Steve H.
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