11-28-2007, 02:53 PM
Have always struggled with atmospheric type effects rendered from max when combined in a compositing package afterwards as a separate layer whether it is glows or afterburn etc. If you want it to look like it did in the VFB no matter how you interpret the alpha it will look incorrect, usually a bit green, so you end up ignoring the alpha and using a screen or an additive mode but you obviously loose the effect of the alpha channel.
Have just come across the "Luminescent Premul" transfer mode in After Effects which helps out a lot when compositing fire elements. In combustion the blending mode is called "Fully Additive Mix", from what I can gather they do the same thing. I'm sure many of you will already be aware of this but I just thought I would post this as it has eluded me for a long time! If i am still missing something then please let me know but if these transfer modes are the way forward then can i suggest they are mentioned in the help files of afterburn and fumeFX etc in the future to stop people scratching there heads when things don't look as one expects.
Below are the explanation from the respective help files:
Fully Additive Mix - Adds non-opaque pixels of the current layer to the layers behind it, but composites opaque pixels normally. This transfer mode is useful for some keying operations to get a slightly cleaner edge against the background.
Luminescent Premul - Prevents clipping of color values that exceed the alpha channel value after compositing by adding them to the composition. Useful for compositing rendered lens or light effects (such as lens flare) from footage with premultiplied alpha channels. May also improve results when compositing footage from other manufacturers’ matting software. When applying this mode, you may get the best results by changing interpretation of the premultiplied-alpha source footage to straight alpha.
Have just come across the "Luminescent Premul" transfer mode in After Effects which helps out a lot when compositing fire elements. In combustion the blending mode is called "Fully Additive Mix", from what I can gather they do the same thing. I'm sure many of you will already be aware of this but I just thought I would post this as it has eluded me for a long time! If i am still missing something then please let me know but if these transfer modes are the way forward then can i suggest they are mentioned in the help files of afterburn and fumeFX etc in the future to stop people scratching there heads when things don't look as one expects.
Below are the explanation from the respective help files:
Fully Additive Mix - Adds non-opaque pixels of the current layer to the layers behind it, but composites opaque pixels normally. This transfer mode is useful for some keying operations to get a slightly cleaner edge against the background.
Luminescent Premul - Prevents clipping of color values that exceed the alpha channel value after compositing by adding them to the composition. Useful for compositing rendered lens or light effects (such as lens flare) from footage with premultiplied alpha channels. May also improve results when compositing footage from other manufacturers’ matting software. When applying this mode, you may get the best results by changing interpretation of the premultiplied-alpha source footage to straight alpha.