Mental ray renders frame fraction

# 1 18-05-2013 , 07:16 PM

EduSciVis-er
Join Date: Dec 2005

Location: Toronto

Posts: 3,374

I've got another weird mental ray problem that I can't find a solution through google. I noticed that my main render layer was rendering slightly offset from my other layers, like AO. After some investigation, I notice that when I hit render, mental ray does "translating frame 24" and the timeline skips back to 23.80 and then forward to 24.20 and then it renders out 24.20. Which is causing the offset, I believe. All my keys are on whole frames, and I don't have any motion blur. My other layers render on the whole frame, even the masterLayer, it's just the one that is weird. What gives?

Other stuff in scene: I've got hair that's cached, and rigged and deforming geometry. FG is on, IBL, rendering out as openexr at 32-bit.

-stwert

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# 2 18-05-2013 , 07:18 PM

EduSciVis-er
Join Date: Dec 2005

Location: Toronto

Posts: 3,374

Wow... figured it out. It often just takes formalizing my issue to narrow it down. I did not have any motion blur on (I read somewhere that mr calculates 0.2 of a frame in either direction). But I forgot that I did have a motion vector 3D pass associated with the layer, and so of course that was it.
That's got to be a bug that it renders out the fractional frame when you have a mv pass. That's terrible.

-stwert

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# 3 18-05-2013 , 07:23 PM

EduSciVis-er
Join Date: Dec 2005

Location: Toronto

Posts: 3,374

And a potential solution: https://cruelyeti.blogspot.ca/2012/08...ental-ray.html

Turns out I don't really need the vector pass after all, so I'm just going to disassociate it and re-render. Note that this happens with both 3D and 2D vector passes.