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Why use "Do Not Premultiply Alpha"?
Posted: Thu Jul 21, 2011 1:40 pm
by 3deeguy
Can it be used for things like scene changes? Instead of putting individual scenes together in an external movie editor can separate videos be lined-up in the sequencer and re-rendered? At least I would then be able to sync all my clips to a single music track.
I started studying particle layers last night wondering what it would take to create an 'explosion in space'. This is such a large subject that I might have to put it off for a while.
Posted: Thu Jul 21, 2011 2:43 pm
by slowtiger
"Pre-Multiply Alpha" is a term used for rendering images on a transparent background. The two options are "Pre-Multiply Alpha" and "No Pre-Multiply Alpha". The first one is useful for darker outlines, the second for lighter outlines, and they'll prevent to have thin white or dark rims later in compoisting images on a background image.
Posted: Thu Jul 21, 2011 3:12 pm
by 3deeguy
Sounds like a way to keep composited images from looking like cut-outs. Thanks slowtiger. It's time to give myself another mental break then come back and do some tests.
Posted: Fri Jul 22, 2011 1:43 pm
by hayasidist
hi. also if you have soft edge then without "do not premultiply" the soft edge is blended with the bg colour ... as I found out the hard way ...
viewtopic.php?p=105407
with "do not premultuiply" the bg does appear not to be blended into partially transparent areas. (and apols to Ramón cos I forgot to say thanks back then!)