----- Original Message -----
From: Glenn Bech <130### [at] swineduau>

> Q1) I suspect the answer is YES from observation, but I wonder why.... Why
> does pigments affect
> 100% reflecting surfaces ? If I had a red texture, with 100% reflection,
it
> would look different
> than a blue texture with 100% reflection, or ??? Are there any use at all
to
> have a pigment for example
> when using 100% reflective surfaces ?

    How it works (I think this is all correct): "Reflection 1" is not "100%
of what you see is reflection" but "Adds 100% of the reflected image into
the mix".

    So "Reflection 1 diffuse 1"  [you get diffuse 1 or close to it by
default, if you don't specify it to be less] means

    Light from object is 100% of reflected image + 100% of (diffuse lighting
* color)

    "Reflection 1 diffuse 1 ambient 1" means

    Light from object is 100% of reflected image + 100% of (diffuse lighting
* color) + 100% of color

    This means that such an object will typically give off more light than
hits it, which is why "hall-of-mirrors" scenes tend to get so bright. The
objects are, as it were, "lasing"! A ray bouncing off four "diffuse 1
reflection 1" mirrors will consist of:


    After first object (assumed lit but not reflecting): diffuse light1 *
color1

    After second mirror: (diffuse light 1 * color 1 ) * 100% reflection +
diffuse light 2*color 2

    After final mirror:

(((diffuse light 1 * color 1 ) * 100% reflection + diffuse light 2*color
2)*100% reflection + diffuse light 3 * color 3) * 100% reflection + diffuse
light 4 * color 4.  This is the same as "color1 + color2 + color3 + color
4", usually white!


    As a real mirror does not emit energy, it follows that whoever would
create a realistic raytraced mirror should always ensure that
ambient+diffuse+reflection <= 1.0.  If you don't want realism, do what you
like!

    -Robert Dawson

Post a reply to this message