Hi, Struggling with some serious motion blur artifacts with Karma XPU. Karma CPU does not have them.
(1) below shows the artifacts. (2) below is correct. (2) can be achieve by either using CPU only or disabling per-Object Motion Blur (3). Am pretty sure is related to the vblur console error getting (4), so can't find anything about this error so don't know how to fix it. Presumably disabling per-Object Motion blur is stopping the error from happening (but obviously need that motion blur so it's not a fix). Neither is using CPU only as render times triple.
An additional note regarding the artifacts: KarmaXPU also doesn't display them when the GPU takes a while to load, seems the motion blur is processed on CPU then, even while using XPU. Render machine used above is dual 4090, 5995wx, 256gb ram. Single card does not affect. Bug also occurs on a 3090, but not on 2080Ti and 3060, although believe this is because the cards are slower so the motion blur calculations are being done by the CPU. Tested across multiple rigs, is not a hardware related issue.
Are you then able to reproduce the issue on all types of GPUs? (I ask this because we have had issues with motionblur on different types of GPUs)
In the scene you've provided, does it have a solaris scene in there somewhere? If so, how do I navigate to it? (ie, how are you activating KarmaXPU and where are the render settings)
So the vblur console error is caused by packing the model prior to rigging, disabling the Pack (arrow below) fixes the vblur error and fixes the artifacts. Obviously not really a solution as packing pretty essential:
Drivers, don't change anything, tried previous studio and also latest 551.61 KarmaROP is in OUT - for some reason rendering in OUT rather than via stage took over 2min off the USD compile time vs sceneimporting into stage. Still not sure why KarmaCPU / KarmaXPU (only using CPU) shows no artifacts with vblur error but KarmaXPU (using GPUs) shows artifacts with vblur error?
cgfrankie Still not sure why KarmaCPU / KarmaXPU (only using CPU) shows no artifacts with vblur error but KarmaXPU (using GPUs) shows artifacts with vblur error?
most likely an Optix/Driver/GPU issue.
cgfrankie Bug also occurs on a 3090, but not on 2080Ti and 3060
With the EmbreeCPU device disabled using the environment variable KARMA_XPU_DISABLE_EMBREE_DEVICE=1
Are you then able to reproduce the issue on all types of GPUs? (I ask this because we have had issues with motionblur on different types of GPUs)
Issue persists using KARMA_XPU_DISABLE_EMBREE_DEVICE=1 with only GPUs running unfortunately:
Why is the Pack causing the vblur, because if that is fixed the whole problem is fixed, as disabling the Pack fixes the issue.
There is a small workaround for the vblur Pack issue it seems which is unpacking then re-caulating the velocity at the end of the node chain, but means can't properly instance things so also isn't a fix.
cgfrankie Issue persists using KARMA_XPU_DISABLE_EMBREE_DEVICE=1 with only GPUs running unfortunately
Is this with multiple GPUs running at the same time? Or were you able to test each gpu individually?
cgfrankie Why is the Pack causing the vblur, because if that is fixed the whole problem is fixed, as disabling the Pack fixes the issue.
There is a small workaround for the vblur Pack issue it seems which is unpacking then re-caulating the velocity at the end of the node chain, but means can't properly instance things so also isn't a fix.
Thanks for the info. Will investigate in the next day or two.
