 | | | premultiplied alpha | premultiplied alpha 2004-03-10 - By Marc Trzepla
Back
Yeah, I got tired of this too, and now output everything as Straight fills
from Photoshop (an action) and After Effects. The black is really
noticeable on lower-than-I'd-like-it resolution maps ... they become usable
as straight.
marc
>From: "Andy Hayes" <ahayes@(protected)>
>Reply-To: XSI@(protected)
>To: <XSI@(protected)>
>Subject: RE: premultiplied alpha
>Date: Tue, 9 Mar 2004 18:38:31 -0000
>
>i guess the only way is to generate the desired over is to make the
>additive
>mix nodes in the rendertree - ie the 'over' composite equivalents:
>
>a premultiplied 'over' would be equal to Argb + (( 1 - Aa) * Brgb)
>
>and a normal 'over' would be equal to (Argb * Aa) + (( 1 - Aa ) * Brgb)
>
>where A and B are the images for the 'A over B' configuration and 'rgba'
>the
>color channels.
>
>You can knock up the tree fairly easily in the rendertree.
>
>also, to remove the 'premultiplied' notion from an image simply divide its
>rgb values by the alpha, and use a straight forward additive mix
>
>a bit ot but may be useful?
>
>Andy
>
>-- --Original Message-- --
>From: owner-xsi@(protected) [mailto:owner-xsi@(protected)]On Behalf
>Of kim aldis
>Sent: 09 March 2004 16:24
>To: XSI@(protected)
>Subject: RE: premultiplied alpha
>
>
>Strictly speaking, un-premultiply. I've never found one. Try feeding the
>alpha into a mix2nodes, put the image into one node and make the other a
>lighter colour. Something approaching the colour of your image. Not ideal,
>I
>know but that's about the best I've found so far.
>
> > -- --Original Message-- --
> > From: owner-xsi@(protected)
> > [mailto:owner-xsi@(protected)] On Behalf Of Jamination@(protected)
> > Sent: 09 March 2004 15:58
> > To: XSI@(protected)
> > Subject: premultiplied alpha
> >
> > when i apply maps with alphas to objects (as decals) i'm
> > getting some black halos around the image. is there a
> > premultiplied option anywhere to help me remove this effects,
> > i'm struggling to find anything.
> >
> > thanks
> > phil harbath
> > jamination
> > ---
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> >
>
>
>
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