In article <3A0### [at] ijnet>, Matt Giwer <jul### [at] ijnet> wrote:

> 	Playing with ambient is one of the ways of faking it. If there is no
> illumination, why should anything be visible regardless of the ambient?

But there *is* illumination. You specified a 50% gray ambient lighting.
Think of it this way: there is a global ambient light source which 
defaults to white. It has no direction or location, so it illuminates 
the scene evenly, is not shadowed or shaded. The color of this light is 
specified by the "ambient_light" keyword in global_settings. Textures 
have an "ambient" component which specifies how much they are affected 
by this ambient light, the two colors are multiplied together and the 
result added to the illumination. The ambient_light keyword gives you a 
way to globally change the ambient values, and the ambient finish 
attribute allows you to control it on a per-texture basis.
Since the default is "ambient_light rgb < 1, 1, 1>", and you specified 
ambient 0.5(which is the same as "ambient rgb < 0.5, 0.5, 0.5>"), what 
you did is tell POV to add rgb < 0.5, 0.5, 0.5> to the illumination of 
each point on the sphere.

Actually, the "ambient_light" keyword isn't even necessary, you can do 
something like this:
#declare AmbLgt = color rgb < 1, 1, 1>;
...
texture {
    ...
    finish {
        ambient AmbLgt*0.5

However, variables may not have existed when ambient_light was added.


> I just want things to behave according to the scene description. 

It is, I assure you. :-)


> 	I have this image of the light reflecting off of the camera ...:)

More like a fill light at the camera position that doesn't leave shadows 
and isn't affected by the contours of the surfaces(no shading). Ambient 
is actually intended as a quick-and-dirty way to simulate diffuse 
illumination, light bouncing off of other objects, but radiosity does a 
much better job of that. Since ambient light can be specified per-object 
and is added to the ordinary illumination, it is often used to make 
glowing objects.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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