about the time we think we can make ends meet,
somebody moves the ends. - Herbert Hoover

Concept 5 : RGB Values for Lights and Materials
===============================================

Idea:
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Having seen the different components of lights and 
materials, let us now look at their interaction.

Theory:
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The color components specified for lights mean
something different than for materials.  For a light,
the numbers correspond to a percentage of full
intensity for each color.  If the R,G, and B values
for a light's color are 1.0 the light is the
brightest possible white.  If the values are 0.5, the 
color is still light, but only at half intensity so
it appears gray.  If R=G=1 and B=0 ( i.e. full red 
and full green with no blue), the light appears
yellow.  

For materials the numbers correspond to the reflected
proportions of those colors.  So if R=1, G=0.5 and B=0 
for a material, that material reflects all the incoming 
red light, half the incoming green, and none of the
incoming blue light.  

Example:
========
If an OpenGL light has ocmponents (LR, LG, LB) and a 
material has the corresponding components (MR, MG, MB) 
then ignoring all other reflectivity effects, the light that
 arrives at the eye is given by (LR*MR, LG*MG, LB*MB);

Similarly if we have two lights OpenGL just adds the red,
green and blue components and clamps the results to 1.