Mon Dec 18, 2017 4:11 pm
This must be user error because it's just too essential to be a bug -- I can't seem to get a simple alpha channel to composite cleanly in Resolve. This breaks down to two possibilities, one of which is user error, the other might be a really disappointing limitation of Resolve.
Specifically, I've run into two problems with alpha channels:
1.) Alpha channels show visible artifacts on clean edges that comp correctly in all other environments
Here's a shot where I'm re-projecting a rooftop to add some CG elements. The seam is roughly along the edge of the building:
If we zoom in, you can see there's a little bit of an aliasing issue where the reprojected roof meets the building behind it, even though at this point the projections match up perfectly and the image is actually identical (except for the presence of the alpha channel and of course some filtering from the projection):
(click through to see full res, the downsampling for image preview kind of obscures the aliasing)
It's much clearer with a grade, and frankly not an acceptable result:
This is a simple premultiplied alpha channel in an EXR sequence. In literally any other app, even Premiere, this looks fine.
Fusion:
Nuke:
Premiere:
Is there something that can be done to composite this correctly? I've tried piping the EXR's alpha channel directly into an additional alpha output as a matte bypassing the other nodes, but it seems to make no difference (not that I'd expect it to if the artifact is visible even when the grades are disabled).
How are people working around this if it's just a bug in Resolve? Also, I did check to see if this was either a scaling issue or a preview render issue -- neither is the source of the problem and this is very visible in the final outputs.
2.) Using frame blend and / or optical flow completely destroys the alpha channel.
This one is probably just a bug -- or a simple limitation of Resolve. Using any retiming process other than Nearest results in a ruined alpha channel:
Frame Blend:
Optical Flow:
That's just... not really acceptable as a result. Again, other apps do not have this issue:
Nuke (tested OFlow, Kronos, TimeWarp, Retime):
Premiere (tested Frame Sampling, Frame Blending, Optical Flow):
This is pretty disappointing. I'm open to the possibility that I'm doing something wrong here, but the fact that Premiere of all apps is performing these simple channel operations correctly while Resolve fails so visibly is really not making me happy. So what's the deal?
System Specs:
OSX 10.11.6
2013 Mac Pro (max spec)
Resolve Studio 14.0.1
Specifically, I've run into two problems with alpha channels:
1.) Alpha channels show visible artifacts on clean edges that comp correctly in all other environments
Here's a shot where I'm re-projecting a rooftop to add some CG elements. The seam is roughly along the edge of the building:
If we zoom in, you can see there's a little bit of an aliasing issue where the reprojected roof meets the building behind it, even though at this point the projections match up perfectly and the image is actually identical (except for the presence of the alpha channel and of course some filtering from the projection):
(click through to see full res, the downsampling for image preview kind of obscures the aliasing)
It's much clearer with a grade, and frankly not an acceptable result:
This is a simple premultiplied alpha channel in an EXR sequence. In literally any other app, even Premiere, this looks fine.
Fusion:
Nuke:
Premiere:
Is there something that can be done to composite this correctly? I've tried piping the EXR's alpha channel directly into an additional alpha output as a matte bypassing the other nodes, but it seems to make no difference (not that I'd expect it to if the artifact is visible even when the grades are disabled).
How are people working around this if it's just a bug in Resolve? Also, I did check to see if this was either a scaling issue or a preview render issue -- neither is the source of the problem and this is very visible in the final outputs.
2.) Using frame blend and / or optical flow completely destroys the alpha channel.
This one is probably just a bug -- or a simple limitation of Resolve. Using any retiming process other than Nearest results in a ruined alpha channel:
Frame Blend:
Optical Flow:
That's just... not really acceptable as a result. Again, other apps do not have this issue:
Nuke (tested OFlow, Kronos, TimeWarp, Retime):
Premiere (tested Frame Sampling, Frame Blending, Optical Flow):
This is pretty disappointing. I'm open to the possibility that I'm doing something wrong here, but the fact that Premiere of all apps is performing these simple channel operations correctly while Resolve fails so visibly is really not making me happy. So what's the deal?
System Specs:
OSX 10.11.6
2013 Mac Pro (max spec)
Resolve Studio 14.0.1
"It's amazing what you can do when you don't know you can't do it."
Systems:
R16.2.3 | Win10 | i9 7940X | 128GB RAM | 1x RTX Titan | 960Pro cache disk
R16.2.3 | Win10 | i9 7940X | 128GB RAM | 1x 2080 Ti | 660p cache disk
Systems:
R16.2.3 | Win10 | i9 7940X | 128GB RAM | 1x RTX Titan | 960Pro cache disk
R16.2.3 | Win10 | i9 7940X | 128GB RAM | 1x 2080 Ti | 660p cache disk