"Bob H." wrote:
> Light sources still
> only use the usual linear, quadratic, etc., fading.

Of which the fade_power 2 is the physically accurate one. Actually
it is calculated so that it is accurate for a light source with
non zero dimensions which is better than 1/r^2 because most real
light sources are not point sources.

I'm anticipating some responses to this so here is some more. Light
_does_not_ fade in vacuum because there is some mysterious "ether"
in there. The fading is caused by simple geometry. Let's say a point
source at the center of a 1 m radius sphere emits 1 W of energy. The
inside of the sphere receives 1 W of energy. The surface area is

1 W of energy (no ether). The surface brightness of the sphere has
decreased because the energy per area has decreased. The area is now

This where the 1/r^2 comes.

Even lighting engineers don't bother to calculate the effect of
absobtion caused by air but it's possible in povray. Put
media_attenuation on in the light sources and some media in the scene.
The effect is visible over large distances, like 1 km.


_____________
Kari Kivisalo

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