Alain <aze### [at] qwertyorg> wrote:

> > I am getting v. confused.
> >
[]

> > 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)?
> >
[]

> 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 }}

[]

Dear Alain and Stephen

Thank you so much for this explanation.  You have done a great service for my
sanity - I was going batty trying to work it out. (Still not quite sure why the
alpha channel version rendered a non-white circle, but happy enough am still
sane.)

Regards

G

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