- Posts: 163
- Joined: Tue Apr 26, 2016 12:20 pm
Hi!
I'm stucked again with a starting level problem, this time with alpha management in keyed footage. Hope someone has some advice for me.
EDITED: I have a simple 3d composition, foreground layer is an ImagePlane3D with chroma keyed footage assigned to it. At some point I want to defocus that fg layer. Defocus affects all RGB and alpha channels and, as the input for the defocus node has a black background, after defocusing I get darkened edges, wider as the defocus grows in size. Old classic issue, isn't it?
I've tried to divide (un-multiply) the alpha channel before the defocus, but i'ts not working, as the divide node only affects a few pixels on the borders of the matte, and later I want to make a strong defocus effect.
This only happens with 3D composition. I've just tested it with a 2D composition (simple merge node), and you can defocus a keyed layer as much as you want witout border issues going to black. Fusion manages the alpha perfectly fine within a merge node.
I have a work around this problem, by switching to real 3D multipass depth of field effect, instead of 2D defocusing the keyed footage. That way I avoid messing with any alpha channel. But render times will explode, as strong defocus via depth of field will need a LOT of passes to render clean.
Before taking that painful work-around... Anyone to give me cue on how to defocus a keyed footage in Fusion 8 without messing the matte borders to black?
Thanks in advance!
I'm stucked again with a starting level problem, this time with alpha management in keyed footage. Hope someone has some advice for me.
EDITED: I have a simple 3d composition, foreground layer is an ImagePlane3D with chroma keyed footage assigned to it. At some point I want to defocus that fg layer. Defocus affects all RGB and alpha channels and, as the input for the defocus node has a black background, after defocusing I get darkened edges, wider as the defocus grows in size. Old classic issue, isn't it?
I've tried to divide (un-multiply) the alpha channel before the defocus, but i'ts not working, as the divide node only affects a few pixels on the borders of the matte, and later I want to make a strong defocus effect.
This only happens with 3D composition. I've just tested it with a 2D composition (simple merge node), and you can defocus a keyed layer as much as you want witout border issues going to black. Fusion manages the alpha perfectly fine within a merge node.
I have a work around this problem, by switching to real 3D multipass depth of field effect, instead of 2D defocusing the keyed footage. That way I avoid messing with any alpha channel. But render times will explode, as strong defocus via depth of field will need a LOT of passes to render clean.
Before taking that painful work-around... Anyone to give me cue on how to defocus a keyed footage in Fusion 8 without messing the matte borders to black?
Thanks in advance!
Last edited by Ignacio de La Cierva on Tue Aug 09, 2016 4:53 pm, edited 2 times in total.