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Ben Dewalle avatar image
Ben Dewalle asked

Motion blur on procedural meshs

Hi there

I am trying to render some motion blur on procedurally generated meshs (paint effects transformed as meshs).

The motion blur goes completly crazy on some frames and on some meshs parts, as some vertex had huge movement between frames. I checked the subframes in maya, and they are correct.

I tried baking the meshs as abc with subsamples (0.25), the subframes are ok in maya viewport but the same kind of moblur problem arise.


The vertex id of the meshs change per frame. Do Mtoa need a consistent vertex id during animation to calculate the motion blur?

Or does the problem come from something else?


Thanks

proceduralsmotion blur
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Stephen Blair avatar image
Stephen Blair answered

For a varying topology, you can use the motion vector source:

https://docs.arnoldrenderer.com/x/H4E7B

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Stephen Blair avatar image
Stephen Blair answered

Does the number of vertices change? Is there anything in the Arnold log?

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Ben Dewalle avatar image
Ben Dewalle answered

The number of vertices does change between frames (the meshs is created based on another mesh deformations and the camera animation).

Arnold log throw those errors:

00:00:02  1517MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 14655 -> 14600
00:00:02  1525MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 15055 -> 15050 
00:00:03  1532MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 14655 -> 14610
00:00:03  1535MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 15055 -> 15035
00:00:04  1539MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 15055 -> 15070 
00:00:05  1540MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 14655 -> 14660 
00:00:05  1541MB ERROR   | [mtoa.translator]  pfx_geoShape | Number of vertices changed between motion steps: 15055 -> 15035 


It seems logical that the vectors can't be correctly computed...

Is it possible to set some velocity vector on an attribute vertex for mtoa to read at render time?

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Ben Dewalle avatar image
Ben Dewalle answered

Thanks Stephen!

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