Motion blur on stationary objects using mv2dnorm Pass?

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  01 January 2013
Motion blur on stationary objects using mv2dnorm Pass?

I'm having trouble getting a good motion blur pass from Maya to composite in Nuke. The camera is panning from right to left and so, as you can see from the image, the blur is going the wrong way and looks incorrect (I've amped up the multiplication for the sake of demonstration).

I'm rendering out into EXR format using Mental Ray in Maya 2013 using a mv2dnormremap pass (Max Pixel Disp. = 256) on a dedicated render layer with just a white surface shader on my objects and everything else with its primary vis off. I'm wondering if the problem has something to do with the fact that my object is stationary. I've read that rendering with raytrace will not achieve a motion vector for stationary objects and that rendering with Scanline will, though I tried this and there was no improvement. I have also adjusted the necessary settings in order to (hopefully) counter the .5 off-set issue by setting the shutter close to 0 and also the motion back offset to 0 in the motion blur settings.

Would using mip_motion vector shaders be a viable alternative? Or mv2dToxic? Perhaps there is a problem with my tree in Nuke? NB. Setting the add uv value to -0.5 in the MotionVector node in Nuke gives me no motion blur at all.

I'm pretty new to all this, of course I can provide more information about my set up.

Thanks in advance

  01 January 2013
Post motion blur seems to be killing most people.

Thought about seeing how long the frame is with in-render motion blur and Unified Sampling?
My opinions are always my own...and maybe a friend's, but never my employer's.
  01 January 2013
<Edit> Oops, accidentally posted from the wrong account

Last edited by Starbuckle : 01 January 2013 at 10:47 AM.
  01 January 2013
I took your advise and got good results, so the problem is no longer intractable (phew). However, I would just really like to conquer these motion vector pass problems for my own peace of mind. Do you think the fact that my object is stationary could be a problem?

I tried using a mip_motion_vector shader, even though I know they cause Mental Ray to crash in Maya 2013. I created a new framebuffer and that seemed to improve things, and ensured that the Legacy Output Shader settings on my render cam were set to 'Colour', 'Depth' and 'Motion Vector' and Motion Blur was set to 'Full'. I am rendering out in 32-bit floating and so I wanted to check 'float' as opposed to 'byte' or 'short' but oddly enough it's missing from the attribute options which look a bit messed up (See below - note 'Shor' as opposed to 'Short').

Unfortunately I'm not getting anything that resembles motion vector information in my renders (no green or red, just whatever materials are assigned, in this case a white shader). Have I missed out something fundamental or is the whole enterprise a a non-starter in Maya 2013?
  01 January 2013
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