"PoD" wrote:
> So you're saying that the colour should be simply
> (1-t)*pigment + t*background ?

Yep. Just like it is for values between 0 and 1.

> Sounds good to me.  I've used strange transmit values
> to modify the background colour but in that case I
> usually use rgbt of <0,0,0,SomeOddValue> so the change
> would not affect me.

Here's an inverting pigment:
pigment {color rgb 0.5 transmit -1}

It works in official POV-Ray, but not in MegaPOV.

Here's a contrast-enhancing pigment:
pigment {color rgb 0.5 transmit 2}

However, it doesn't work. It would only work if the transmit value was
changed to work the way I suggest...

> BTW I don't know why MP clamps negative values to zero.

Neither do I and I would *really* like someone to explain it to me...

Rune
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