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Old 01-07-2013, 12:13 PM   #1
DoctorBeat
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Maya Vector Motion Blur output problem

Hi there,
I'm running into a problem with a little video I'm doing, to test a dynamic car rig I've been working on.
The thing is, when I batch render to images everything goes ok, but when a add a motion blur render pass, either the mv2DNormRemap or the mv2DToxik, the wheels start to get increasingly small as they spin faster, at the render time. I cant use the mip shaders since I'm using maya 2013 and it has a bug that crashes mental ray.

I'm rendering to openEXR, scanline+raytrace (otherwise i won't have camera movement motion blur), and i'm running out of options... the problem happens when i set the shutter open and close to 0.5, but if i leave it to 0 it won't give me any motion blur...

I'm applying the motion blut in Nuke using the vector blur node

here are some images





thanks in advance for any help
 
Old 01-08-2013, 11:41 AM   #2
philme
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my workflow is mv2dtoxic

scanline, motion blur to full or no deformation(depending if there is vertex anim)
motion blur by:1
shutter open/close:1
customMotionOffsets:1

think you dont have to mess with those settings in maya2013 if you apply the mv2dtoxic as a pass...

if you import the camera as a fbx into nuke then u also get easy cam motion blur
 
Old 01-08-2013, 12:49 PM   #3
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Vector blur doesn't take rotation into consideration. It will only calculate an angle and distance traveled between 2 frames for a certain point on the mesh. Then the compositing app applies a directional blur using this angle and distance. This will never look good on rotating things like your wheels here. The mip_motionblur shader does the same thing so you don't even need to try that one.

You could render the wheels separately though, and use real raytraced motionblur just for them. You might need to increase motion steps a bit to make them look more realistic.
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Last edited by lostparanoia : 01-08-2013 at 12:56 PM.
 
Old 01-09-2013, 10:55 AM   #4
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Hold on guys, I might be onto something :-)

let me do a couple renders

By now, it would be much faster to have rendered with regular motion blur, and be done by now, but I wouldn't have learned so much.

:-)
 
Old 01-11-2013, 08:36 PM   #5
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hey

thanks for the help
unfortunatly the mv2toxik pass doesn't work either, and thanks to the reply from lostparanoia I know why now :-)

well I rendered without motion blur, because for the result it's not that important and because of a problem that occurs when motion blur (true motion blur) is enabled: the wheels shift place when they spin faster... you can see that problem occur on the following video at around 1:45... it barely noticeable but its there, the wheel shift downward, and i couldn't find a reasonable explanation to that...

https://vimeo.com/album/2215016/video/57202632

anyway thanks for the info :-)
 
Old 01-11-2013, 11:09 PM   #6
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If you have fast spin and fast transformation on a node, the lack of multiple motion transforms in mental ray cause the wobble. If you animate the vertices, say, using a cluster handle and rotating it, this problem is solved. (use full motion blur)

mental ray 3.11 solves the multiple motion transform problem but would need to be changed in Maya for it to export the transforms to mental ray. No idea about that, up to Autodesk.
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Old 01-13-2013, 01:51 PM   #7
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Quote:
Originally Posted by Bitter
If you have fast spin and fast transformation on a node, the lack of multiple motion transforms in mental ray cause the wobble. If you animate the vertices, say, using a cluster handle and rotating it, this problem is solved. (use full motion blur)

mental ray 3.11 solves the multiple motion transform problem but would need to be changed in Maya for it to export the transforms to mental ray. No idea about that, up to Autodesk.


is this common knowledge? I did not know that little trick
Anyway great response, and very useful info, 'cause I'm sure, if you didn't tell me this, this problem would come again to haunt me when I'm on a deadline for sure. That's the way things happen in 3d :-)
Thanks

BTW - your blog is awesome! great tips there

Last edited by DoctorBeat : 01-13-2013 at 03:16 PM.
 
Old 01-15-2013, 08:47 AM   #8
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Quote:
Originally Posted by Bitter
If you have fast spin and fast transformation on a node, the lack of multiple motion transforms in mental ray cause the wobble. If you animate the vertices, say, using a cluster handle and rotating it, this problem is solved. (use full motion blur)

mental ray 3.11 solves the multiple motion transform problem but would need to be changed in Maya for it to export the transforms to mental ray. No idea about that, up to Autodesk.


it seems that mray is fixing all the glitches that we run into in the last months
but i have not faith in an adsk implementation
David, do you know if this kind of change can be integrated under the hood by some developer (like mentalcore) or it┤s something deeper in maya?
i would push much more to have mental core if it solve these kind of glitches
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Old 01-15-2013, 06:15 PM   #9
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Multiple motion transforms would have to be in the translator. mentalcore still relies on mayatomr but under the hood uses clever scripts and presets to correct a lot of things it has access too.

More modern shaders helps too.

Autodesk has renewed and special interest in mental ray it seems. Given the amount of blowback they experienced on the Maya Feedback forum it was clear what users wanted.

Cory Mogk mentioned the separation of mental ray as a plug-in. In 2013 it was nearly complete. You'd have to be on the Beta to see if it has gotten farther. But once that's complete, updates to mayatomr become a separate installation rather than Autodesk needing to release a service pack or hotfix. This is similar to FBX updating.
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Old 01-16-2013, 08:33 AM   #10
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Quote:
Originally Posted by Bitter
Multiple motion transforms would have to be in the translator. mentalcore still relies on mayatomr but under the hood uses clever scripts and presets to correct a lot of things it has access too.

More modern shaders helps too.

Autodesk has renewed and special interest in mental ray it seems. Given the amount of blowback they experienced on the Maya Feedback forum it was clear what users wanted.

Cory Mogk mentioned the separation of mental ray as a plug-in. In 2013 it was nearly complete. You'd have to be on the Beta to see if it has gotten farther. But once that's complete, updates to mayatomr become a separate installation rather than Autodesk needing to release a service pack or hotfix. This is similar to FBX updating.


Thanks for the info, I'll keep an eye on that
 
Old 01-16-2013, 08:33 AM   #11
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