"Warp" <war### [at] tagpovrayorg> wrote in message
news:3dac428c$1@news.povray.org...
> hughes, b. <omn### [at] charternet> wrote:
> > I'd say a logical anti-light would illuminate the shadow regions,
behaving
> > exactly opposite of a regular light.
>
>   Regular light sources have no effect whatsoever on shadows. Negating
> the effect of doing nothing is still doing nothing

I can agree with that, yes. But I have to look differently at the way it
works to get your point about that. I was thinking of a light source as
being the controlling factor of shadows, i.e. have light, have shadow. If
ignoring the existence of radiosity anyhow.

So in that way I was thinking of it as shadows being areas non-illuminated
by regular (positive color) light and illuminated by negative color light.
Although that idea is actually different than what I really expect POV
should do anyhow, I was only wondering what such a thing might be like were
negative lights worked into the program source code.  Affecting shadows in
that way could be interesting, and I'd guess potentially problematic to work
with transparency, to name one of many things.

Anyway, I can see now that negative values for lights do what they should.
That being, subtracting positive light and not affecting shadows (where no
light appears).

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