> I am getting v. confused.
>
> When I render this file (ss.pov):
>
> camera {
>    location<.2,0,2.4>
>    look_at<0,0,0>
>    angle 36
>
> }
>
>
> sphere{<0,0,0>,.5
>      texture {pigment {color rgb<118,23,255>}}
>      }
>
>
> With this command:
> povray ss.pov
>
> I get a white circle on a black background
>
> When I do it with this command:
> povray ss.pov Output_Alpha=True
>
> I get a magenta circle on an alpha channel background.
>
> I assumed that, in each case, since there was no light source, the whole scene
> should be black.  Can someone tell me where the light comes from?
> .... and why rendering with an alpha channel produces different results (outside
> the alpha area)?
>
> Thanks
>
>
> Gobnat
>
>
>

There is no light_source, but there is the default ambient finish of 0.1 
that make that overly bright pigment visible.

color rgb<118,23,255> gives rgb<11.8, 2.3, 25.5> after the ambient is 
applied, and gets clipped to rgb<1,1,1> whitch is white.
POV-Ray use the 0..1 range for the colours.
0 means nothing for that channel, 1 means full intensity for the channel.

Change it to:
texture {pigment {color rgb<118,23,255>/255 } finish{ ambient 0 }}

This turns the ambient off and bring the pigment back in the correct range.

Take note that values larger than 1 are acceptable, but can have 
unexpected results. There are cases where large values are needed, such 
as fading lights.


Alain

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