Hi,

I have just thought of a feature that could be patched into povray, and I
was just wondering if it would actually be possible to do. When I was doing
physics in school, and when we were covering the topic of Light, we studied
how different types of light sources give out different types of
frequencies. As a result, different materials react in different ways to
different frequencies.

The simplest example that I can think of is the difference between an
ordinary yellow lightbulb, and a yellow sodium street lamp. The standard
lightbulb gives out all kinds of frequencies, including red, green and blue
components (much like lights in Povray as they stand).  As a result, red,
green and blue components in the materials the light strikes all reflect
some of those frequencies back, enabling you to continue to discern colours.

However the light given out by a sodium based streetlamp is monochromatic.
While it might look like ordinary yellow light, it isn't. Only specific
wavelengths (ones that our eyes decode as being yellow) are given out - no
greens or blues or anything. So when this monochromatic light strikes
coloured materials, no blue or green wavelengths are reflected. You can
notice this when standing under a sodium streetlight, as the world seems to
be in greyscale (only a yellow-tinted greyscale ;) ).

It is the same with direct sunlight, or flourescent lights or whatever -
different types of lights give out different types of frequencies, giving
them a different "quality" (poor word, but a hard thing to describe).

So I was wondering - you it be possible to add this kind of feature to a
raytracer? Would it just be an addition to the light source code (like some
kind of colourmap, except for frequencies)? Or would it be necessary to
specify aswell in textures how they should react to different frequencies of
light? Would it be difficult to add this kind of thing?

Just pondering...

Element

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