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Alembic not importing motion blur
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System Information
Linux Mint

Blender Version
Broken: 2.77 7dc328e
Worked: (optional)

Short description of error

Imported animated alembic mesh not render motion blur with Cycles, even with correct "motion blur / Deformation flag" on and steps set to 12 (for example)

Exact steps for others to reproduce the error
Just Import alembic mesh to see not working motion blur with animated mesh


To Do

Event Timeline

Rod Tebisx ( triaged this task as Confirmed, High priority.
Brecht Van Lommel (brecht) lowered the priority of this task from Confirmed, High to Normal.Sep 2 2016, 11:53 PM

Thanks guys for reviewing this! :)

@Rod Tebisx ( for the motion blur case, are you referring to meshes with varying number of vertices (like fluids) or any kind of meshes? For the first case this is a known to-do with a patch in the works (D2388).

For the case teste, the vertex number is constant, so is it possible to calculate proper motion blur.
Anyway, as an additional step, please check if possible to import "v" vector attribute on points (v is velocity vector attribute coming from Houdini alembic) and use as motion vector to make Cycles 2.5D motion blur.

+1 on the motionblur! Also an option to scale the velocity would be nice, and maybe an option to choose the channelname that provides the velocity as it might be different depending on the app that creates the alembic. Thanks!

Just wanted to check the status on the import-of-animated-camera-focal-length issue:

@Philipp Oeser (lichtwerk) it looks interesting, but too big a feature to put into master for 2.80.

@Sybren A. Stüvel (sybren): yep, not for 2.80, but this is the way to go, right? [having a cache-fcurve-modifier]
Or is there another possibility [from the design point of view]?

I think the approach is pretty nice, as it'll give us a way forward to animate other properties as well.

I am not working on this anymore, although I could resume work. This approach was suggested to me by Campbell as a general way to import custom keyframes from alembic archives. The patch was uploaded for review a few years ago: D2324.

As for the motion blur patch (D2388), it needs some custom parameters to scale the "velocity" vectors with, as most software export the acceleration (dV / dt) and not the velocity (dP / dt).

@Kévin Dietrich (kevindietrich) : thx for getting back! will read those...
Also note that T54050 is the same thing...

Also I am having problems with sequences again:

@Kévin Dietrich (kevindietrich) Glad you came back! Could you please update your patch D2388 for the current code, so we could review and make it to the master finally, cause it's very important for fluid rendering.
If there's something I can assist with, let me know. I'm not a coder anymore, but maybe a can help.

I would also be interested in D2324 to get some love, @Sybren A. Stüvel (sybren): have you checked that?

@Sybren A. Stüvel (sybren), sorry for the late response but I am not actively working on anything Blender related at the moment.

@Kévin Dietrich (kevindietrich) I suspected as much. Thanks for confirming ;-)

Sybren A. Stüvel (sybren) changed Type from Bug to To Do.Thu, Aug 22, 4:59 PM
Sybren A. Stüvel (sybren) renamed this task from Alembic Import issues to Alembic not importing camera focal length or motion blur.

Changing the classification from 'Bug' to 'To Do', as this is a known limitation.

Sybren A. Stüvel (sybren) updated the task description. (Show Details)
Sybren A. Stüvel (sybren) renamed this task from Alembic not importing camera focal length or motion blur to Alembic not importing motion blur.

I have removed the camera focal length from the task description, as that is already covered by T54050.
Now this task has only a single topic: importing data required for computing motion blur (probably vertex velocities is enough).