motion blur error when rendering to a sequence

V-Ray V-Ray for 3ds Max Issues
1

I’ve been trying to fix this for a day now. I’m out of ideas .

( gpu render vray 6 update 1.2 latest nvidia studio drivers nvidia 1080 gpu )

Background cars are vray scene files and foreground drone is a vray proxy

When I render a single frame the motion blur looks correct (like this )

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when I render a sequence the motion blur is smeared on the drone but the hover cars in the background remain the same .

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GPU Render setting look like this

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2

Hello,

I couldn’t reproduce the problem that you have described in a newly created scene. Could you share some additional info like which frame are you rendering for the single frame test, etc. ? In fact, would it be possible to pack an archive and send it over to philip.shounev@chaos.com so we can troubleshoot ?

Best,
Philip

3

same issue with simple sphere rendered with same animation ( motion on the sphere is keyframed not linked to the drone )

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frame is totally different when​ rendered as part of a sequence

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4

Thanks Philip I sent you a mail with a wetransfer link

5

Is it possibly related to this issue when testing a frame in IPR versus production render?

https://forums.chaos.com/forum/v-ray-for-3ds-max-forums/v-ray-for-3ds-max-problems/1027930-motion-blur-in-ipr-totally-wrong-result

6

possibly , but in my case a single ipr frame has the correct motion blur . the bug only appears in GPU rendered sequences of multiple frames

7

I guess it is related to the camera being linked to the drone.

8

Thanks for the suggestion … Alas the camera and drone are not linked and are animated independently . the camera is imported as an alembic . the drone has its own little animation rig .

9

Hi again @kenzor

Thank you for providing a scene. We are currently testing a solution for this problem. So far, we have had positive results. Nevertheless, more testing will be needed before this solution finds a place in the next official release due to its complexity and involvement with other features.

10

@Philip_Shounev If you have identified a particular failing use case of motion blur could you please post the details of the issue so that the rest of us know what to watch out for?

Even if there is no current workaround we like to understand any bugs/issues so we can know what to expect is various situations.

This saves us users hours or days trying to find issues, and workarounds that may not exist and you have already tested.

Thanks.

11

Hello @Joelaff

The aforementioned difference in motion blur appears when a value of 0 is used for interval center. Until our fix for this case is complete and available the issue can be worked around by setting motion blur interval center to a value different than 0. In most cases a value greater than or equal to half of the duration value will suffice.

12

Excellent. Thank you. I have definitely seen some form of this. I thought it was the Phoenix particle shader at the time, but I don’t think I had time to test it thoroughly. ( and forgot to come back to it after the deadline. )

Great that somebody else narrowed it down and it is getting fixed; because in VFX we often need blur that is less than a 180deg shutter, and need control over the offset as well of course.

Thanks.