Daniel Rogers wrote:
There may be some worth in considering including other kinds of information in a pixel besides alpha.

In addition to alpha (the measure of coverage) you could also include transparency (which is something a measure of how much light passes through, i.e. the actual transparency of glass, as opposed the the coverage of a screen, this is equivilent to insisting on a layer mask to be included for every layer).

It is a little tempting, as it would remove a lot of ambiguity in the overloading of the meaning of the alpha channel. We've (well, GIMP and probably most other transparency-handing packages out there) been equating transparency with alpha for so long now though that I'd hate to have to re-educate users. But it needn't be something that the front-end has to expose.

We could also include luminesence, which is a measure of how much light a pixel produces (as opposed to reflectance, which is all we measure how with rgb).

There are various per-pixel properties I could think of which might be very exciting (surface normal vector, specular reflection index) especially for natural media rendering. Luminescence wouldn't be the first that'd come to my mind, since I think that any such image elements would by nature be quite isolated and fit very well on their own 'addition' style layer and save a lot of complexity, but perhaps it would be nice to paint with fire after all...

Adam D. Moss   . ,,^^   [EMAIL PROTECTED]   http://www.foxbox.org/   co:3
busting makes me feel good
kthx bye

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