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VDB motion blur

Posted: Thu Mar 31, 2022 11:03 pm
by jessestormer
I'm having an issue with VDB motion blur...
I have a moving object with a camera chasing it -- it seems to not account for the fact that the camera is keeping up with the VDB at the same speed and should have far less motion blur
Same thing occurs if the camera is attached to the moving object, it only seems to account of the object speed when calculating motion blur and not compensating for the camera speed

I also apparently can't turn off motion blur for just that object using the octane object buffer tag...

Any help you can provide is appreciated!

VDB motion blur.jpg
thruster motion blur.jpg

Re: VDB motion blur

Posted: Thu Mar 31, 2022 11:29 pm
by jayroth2020
VDB assets require separate velocity motion blur channels for each axis, which are generated by the source simulation. If you do not have those channels in the VDB file, it will not motion blur properly.

Read more about it here: https://docs.otoy.com/cinema4d/VDBLoader.html

Re: VDB motion blur

Posted: Fri Apr 01, 2022 12:15 am
by aoktar
Also I don't think that will support the transform based motion blur. And using tag you can't disable motion blur. This option is just defining the object will or will not have keyframes on export.

Re: VDB motion blur

Posted: Fri Apr 01, 2022 4:39 am
by jessestormer
aoktar wrote:Also I don't think that will support the transform based motion blur. And using tag you can't disable motion blur. This option is just defining the object will or will not have keyframes on export.
Thanks for the info/ help!

The crazy thing is ... it does seem to be TRYING to use the transform motion blur, and even doing it well -- but not accounting for the difference of the camera movement.
ie: with a static camera it does seem to be using transform motion blur

Re: VDB motion blur

Posted: Fri Apr 01, 2022 4:39 am
by jessestormer
aoktar wrote:Also I don't think that will support the transform based motion blur. And using tag you can't disable motion blur. This option is just defining the object will or will not have keyframes on export.
Thanks for the info/ help!

The crazy thing is ... it does seem to be TRYING to use the transform motion blur, and even doing it well -- but not accounting for the difference of the camera movement.
ie: with a static camera it does seem to be using transform motion blur

in this use-case I do kind of wish it just weren't providing motion blur at all

Re: VDB motion blur

Posted: Fri Apr 01, 2022 11:22 am
by aoktar
jessestormer wrote:
aoktar wrote:Also I don't think that will support the transform based motion blur. And using tag you can't disable motion blur. This option is just defining the object will or will not have keyframes on export.
Thanks for the info/ help!

The crazy thing is ... it does seem to be TRYING to use the transform motion blur, and even doing it well -- but not accounting for the difference of the camera movement.
ie: with a static camera it does seem to be using transform motion blur

in this use-case I do kind of wish it just weren't providing motion blur at all
I think you are in a wrong impression about object motion blur. Probably due to habits from other renderers and title of parameter. It will be better if we call it like "Object motion export data". Because it doesn't do anything itself. You letting you exporting animation frames accordingly to option. Animation calculation is done by engine and depends to camera settings.
1-"Disable" means there's not any keyframes exported."
2-"Transform" means that only transform keyframes will be exported.
3-"Transform/vertex" means that transform+vertex keyframes will be exported.

So if you select "disable", object will be like non-moving mesh. Anyway you'll see motion blur effect if your camera moving because of relative matrix delta.

At the end, VDB(volume) objects are not supporting transform motion blur. What you see it that Volume is considered static and motion effect is coming from camera vs. object position delta.