Motion Blur -> Geometry popping

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Okay. Sending an email right now with a download link. Would be great if you can find the reason.

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Hi Mihail,

did you have the time to check the scene? Any hints would be great as we need to render out this scene asap.

Thanks a lot,
Lars

[dougWilkinson]

jumping in late here with a simple sanity check, but anytime i see this kind of stuff i always enter the fractional frames in the time slider to see if its indeed a problem in the scene. if we render motion blur duration of 0.5 frames and interval center of 0.0 then starting with frame 100 (for example), i would enter 99.75 in the time slider. then put in frame 100.25. and maybe try a few more in between. if the object is doing the right interpolation in the view-port while you do this then the maya scene is fine.
i'm guessing your maya scene is fine and its something about the vray exporter but its nice to do a sanity check to at least know if the sub-frame motion is working right in the maya scene.

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Thanks Doug for jumping in and for the tip. We already had checked in the VP, but did it once again and all fractional frames looks fine. Now jumps or sudden motions. Nothing.

Meanwhile we gone once again through the rocket geometry and clean and freeze up everything. We also rebuild our little rig setup. As a result the popping gets a bit better: The little coverings are now stable.

But the defragmentation of the rocket still happens. Strange thing is that only the back part of the rocket make these jumps. The nose and the middle part stays intact.

The last solution we will try is to constrain locators to our objects pivots and bake the animation to them. Then get ride off the original animation and parent the objects under the locators. But I have doubts if that helps.

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No way... even baking the motion to a locator doesn't help. What a sh..t! Only annoying solution now it to render the faulty frames without mb and try to fix it in post....

[Morbid Angel]

is it on a motion path? try delete history on the curve it self, I used to have this exact problem when motion curve was edited after the motion path as already built, like adding/removing control points. If you can make a repro scene, please post it as well.

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Hi Dmitry, thanks for tip. As we already had transferred all animation to a locator and delete the motion path, it seems that the motion path is not the bad guy in this game.

We have sent a scene to support last week. Sorry, can't publish the scene. We would need to rebuild with some basics objects, but we first need to finish the job. Hopefully support will find an answer someday. Now we need to try to fix in post.

Lars

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Any news or comments for us from the support team? Thanks, Lars

[hermit.crab]

Thanks for the provided scene and excuse the delayed reply. It seems the issue persists with a lot of variables diminishing its effect (removing the groups' transforms/removing the motion path's twist). Therefore, I've logged the scene (internal bug-tracker id: VMAYA-9867) for development analysis. Lowering the motion blur's geometry samples from the Camera Overrides settings seems to mitigate the issue significantly. I'll inform you of the analysis report upon completion.

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Thanks Aleksandar for the update. Hopefully the developer will find the reason.

We have not use the Camera Overrides in the end, because it doesn't seems to help. But you have used it, right? Can you give me an exact number for the geometry samples that mitigate the issue? We would then try to render the faulty frames with Camera Overrides on and your settings.

Best,
Lars

[hermit.crab]

A value below 8 seems to diminish the effect on my end.

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Thanks for the info. We finally render the scene again with Geometry Samples set to 6. Instead of 80 buggy frames in the whole sequence, we now only have 55. At least some sort of progress.

If you hear some news from the developers, please report back. Thanks for your support.

[jasonazure]

Hi,
I think I am experiencing something similar to this!
I have a camera fixed inside a car (parented) that is driving around, but it seems like the camera's motion blurred motion is 'off' from the motion of the car so the interior is blurring when it should seem perfectly static!
The seats are the most pronounced as they are the closest to the camera.

Maya 2020 - Vray NEXT - Physical Camera with motion blur on.
Any progress on this issue?

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No news from Chaosgroup so far. Never tried to render the scene with v5. So perhaps it it fixed already.

But I'm not sure if your problem is the same: In our case the group hierarchy "fall apart" for the motion blur sampling.

Hope you will find a solution.

[Morbid Angel]

Generally speaking the camera motion blur works correctly. Can you reproduce this case on a simple scene, i.e parent camera to a moving group which has some objects in it? if it does not, then there maybe some issue with the way the scene is setup. Baking out camera might be an option. If you can share part of this scene (simplified for investigation we might be able to shed more light to the issue)