(open,open)[HOU-4238,HOU-4239]Motion blur issues with groom

[luan_simonin]

Hi, I'm having issues rendering a sequence with motion blur. When I turn motion blur on in the ROP it works for everything just fine, except for the groom which doesnt seem to stick to the surface its supposed to be following (hair on a character's head). It is affected by the motion blur, but simply not the same way as the rest of the geo. Is there something that I'm missing, like an option that needs to be ticked? The groom is imported as alembic and we put a few subframes while simulating it, exactly to avoid this issue.

Best regards,
Luan

[bdancer]

Any chance to share issue reproduction setup with us?

[luan_simonin]

Hi bdancer , yes sure! I've simplified the scene and packed it, where do you want me to upload it?

[bdancer]

luan_simonin wherever is more convenient for you. There is an email in my forum signature so you could just send the link there.

[luan_simonin]

bdancer Sent, thank you very much.

[chakarov]

Hi luan_simonin , I've checked your scene and found two main issues. First one is with character hair. Looks like wrong time samples are exported for alembics when motionblur duration is less than 1 frame. You can workaround this by simply unpack the hair. Other issue is with messed body mesh caused by subdivision for some reason. To avoid it you could bake velocity attribute using the trail SOP and enable velocity blur in Geo Node > Render > Geometry Velocity Blur.

[luan_simonin]

Hi chakarov , thanks for the answer! Unpacking does wonders, thanks a ton! About baking the velocity tho, do I just need to plug the trail node at the end of my graph and switch the result type to compute velocity (and then go in geo node, render, etc.)? Because doing so changes my lighting for some reasons, it makes the geo very dark.