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Here’s how to get a working RSMB vector pass out of Blender
A few months back I searched this forum and the rest of the Internet for the solution to this problem, and I couldn’t find anything that actually worked properly, so I finally just had to figure it out for myself. I just remembered that I had meant to come back and post it here in case it will help anyone else avoid having to reinvent the same wheel.
The pictures below show the custom node I created called “Speed to RSMB”, followed by where it connects into the Blender compositor, and then the settings of RSMB Pro Vectors using the resultant vector pass layer in After Effects.
Contents of Blender Speed to RSMB Node:
Blender overall compositor chain (I’m also outputting a depth pass here):
Use of resultant vector pass by RSMB Pro Vectors in AE:
Finally here are a few shots of the resultant render with and without RSMB enabled. These are from a video of an asteroid that is tumbling slowly forward along its longer axis, and doing a close fly-by of a stationary camera that is panning to follow it, causing motion blur both on the asteroid and the stars in the background, and finally the Earth that is unfortunately directly in the asteroid’s path. 🙂 The asteroid, Earth and background were each rendered out as separate passes with their own vector and depth passes, but I deleted all of that out of the Blender compositor picture above to provide a cleaner view of how to connect the Speed to RSMB node.
With RSMB:
Without RSMB:
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9 Replies
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Thanks Bill,
Will post a note about this at some point on our MV Tutorial page…
Pierre
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Hello there! I was looking for the same solution. The images are not loading in this. Do you have the solution posted anywhere else?
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Hello. I still had these projects sitting on my drive so I was able to create some new screen shots of the configuration in Blender and After effects.
Here’s the Blender Speed to RSMB node and overall compositing chain in Blender, and the setup in RSMB in After Effects, which is basically to point the Motion Vectors parameter of RSMB to another layer that contains the RSMB output generated from Blender.
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Thank you so much Bill for the reply and breakdown.
I’m guessing the “2048” is the width of your render or max displacement? or is it a constant value?
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I’m having trouble remember where the 2048 came from, but it’s definitely not the width of the comp, because in this project that was only 720.
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Alright, I’ll try with that value.
Merry Christmas! 🎁⛄🎄
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No point making that value larger than image width. And if rendering 32b float Motion Vectors this can be set to 1 (no scaling, no clamping) – 2048 on a 720 wide images is allowing 3 times the image width displacement which is not a useful thing for this as we are sampling the image content. This value needs to be reflected in Motion Vectors supporting plugins here so be set to same value in plugin. That Max Displace – which has been rebranded by Arnold as Normalize factor – is historically for being able to do space saving storage in 16 bit “short” 0-65535. Half float 16bit can perhaps be used for Motion Blur (not for Twixtor Vectors in though for same reason that 16b float UV map is not precise enough) but half float has almost no precision outside 0 to 1 and ~13 bit from 0 to 1, these should also be using Normalizing Max Displace but for MB purposes I would not go over Max Displace 2048 with half float even if you render 4096 and instead scale Amount in RSMB by 2X then – sampling a motion streak over half the image width length is enough. Note for example Unreal Motion Vector now export auto-normalize to width which starts to be low-res a lot on 8K with half float.
Pierre
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Bill, I missed that one. I would be happy to test your results and document it on our website. I don’t use Blender here aside once in a while having to open a project so a bit useless. A good test is to 1) render a static scene and see R=0.5 and G=0.5 and 2) use an easy to measure dimension example 1000×1000 px image and animate a rectangle moving say 10 pixels per frame in X then in Y – i.e. animate a rectangle going from left to right in 100 frames (fully out entering frame on left to fully out exiting frame on right) so we can actually measure all is fine…
techsupport @ revisionfx dot com
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