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tech365
05-22-2005, 08:39 AM
How do I render with an alpha channel in the backdrop instead of black .

toby
05-22-2005, 03:53 PM
As long as you're outputting a 32 bit image, you will have an Alpha. If you want it to be 'premultiplied' ( black matte removed, showing transparency ) .PNG32 is the only one I know that will do it straight out of LW.

You will still be able to see a little black fringe however. If you are rendering stills, bring it into Photoshop and apply: Layers/matting/remove black matte. If it's an image sequence, use After Effects and set the premultiply with black. These steps do not require the use of .PNG32, but this format will save you the trouble of selecting all the black and deleting it, in the Photoshop exampe - After Effects and most other compositing programs can set black, including the fringe, to transparency for you in any format that has an alpha.