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View Full Version : RPF Motion Blur with 3ds max and After Effects

amv256
05-17-2006, 11:38 PM
I'm using After Effects to composite a multi-layer animation:

1) I render the layers in 3ds max and save the frames as RPF files.
2) I import the RPF sequence into combustion and apply RPF motion blur, then render the result out as a TIFF sequence.
3) I import the finished TIFF sequences into After Effects for compositing.

Everything is fine except the motion blur effect is compositing badly once it gets into AE. The blur effect itself seems as if it's blending improperly with the lower layers; it has a very harsh, "obvious" look to it. The layers are premultiplied, and I've double checked the settings multiple times to make sure they're all correct.

Is there anything obvious I'm missing? I can't figure out any specific things I could do differently, but I certainly can't leave it as-is.

I know 3ds max and AE very well but I have next to no knowledge of combustion-- I just use it for doing RPF effects in post like motion blur and DOF and passing it on to AE. Can anyone explain what I'm missing?

Thanks! :)
amv256
05-23-2006, 05:37 AM
Nothing? Anyone? :)
thatoneguy
05-23-2006, 10:28 AM
Have you tried reimporting the blurred sequences back into combustion to see if the files themselves are the problem, or if its an interchange problem?

I tried experimenting by creating a sphere, exporting a full RPF. Bluring it in Combustion, and exporting both a multiplied and unmultiplied render to a tiff.

I brought both back into combustion, and (actually told combustion to assume both were pre-multiplied for best results... It hink that's a bug in combustions handling of tiffs, seems to be something I remember hearing) they both when placed on a white background loooked identical to the original RPF blurrred on a white background. I imported the tiffs into photoshop and they both looked identical to the other 3.

I experimented further this time rendering out the same image on a white environment. The resulting blurred image was dramatically different. (On a white composite, it was also dramatically better.)

Someone wiser and more experience than myself should probably come to the conclusions on just what the problem is, but I suspect if you try the composite in combustion with the tiffs you'll encounter the same problem. For that matter, I believe if you attempt the composite in combustion with the RPFs, you'll still see the same artifacts. It's worth a test, let us know how it goes. My suspicion is that the RPF blur is actually pre-multiplying within the operation, which would I could only guess means you would need to double divide it, something I would like to try tommarow in shake with one of the tiffs. I'll let you know about the results.
amv256
06-02-2006, 08:57 PM
I think I may have it fixed.

Like you, I also noticed that there appeared to be a "double premultiplying" going on. To combat this, I exported the TIFF sequence without premultiplication, and once in AE it appeared to blend perfectly.

I know you mentioned doing this as well, but in the case of Combustion -> AE it appears to work. Time will tell as I render some more complicated animations and really put it to the test, but in the relatively simple test I ran, it went from failing to working with that single change.
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