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Alembic not importing motion blur
Confirmed, NormalPublicTO DO

Description

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

Event Timeline

Rod Tebisx (rod.vfx.td) lowered the priority of this task from 90 to High.Sep 2 2016, 10:59 PM
Rod Tebisx (rod.vfx.td) updated the task description. (Show Details)
Brecht Van Lommel (brecht) lowered the priority of this task from High to Normal.Sep 2 2016, 11:53 PM

Thanks guys for reviewing this! :)

@Rod Tebisx (rod.vfx.td) 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: https://developer.blender.org/T51820

@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) renamed this task from Alembic Import issues to Alembic not importing camera focal length or motion blur.Aug 22 2019, 4:59 PM
Sybren A. Stüvel (sybren) edited a custom field.

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

Sybren A. Stüvel (sybren) renamed this task from Alembic not importing camera focal length or motion blur to Alembic not importing motion blur.Aug 22 2019, 5:57 PM
Sybren A. Stüvel (sybren) updated the task description. (Show Details)

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).

For those who haven't noticed, I updated and fixed the patch D2388, please try it if you can!

I have some blurriness, but it doesn't seem to look right. (see Images)
This is a particle system that I exported and then reimported to reverse the movement. And the plane is a dupliobject on the vertices of the ABC.
I would not expect to see a clear outline of the plane in the image with motion blur. Also, the position of the blur is set to Center. But this seems more like Start. And the shutter duration also has no effect.

I also attached a simplified blendfile (+ cache) which has the same issues.
Let me know if I did sth. wrong.

I updated to the latest daily build half an hour ago before testing.

You have to apply the patch and compile Blender to test the feature, it is not in the daily builds. Also your file does not have velocity information (the array size is 0). So without the patch and without custom velocities, Cycles is just using an interpolation between the previous, current, and next frames.

You have to apply the patch and compile Blender to test the feature, it is not in the daily builds. Also your file does not have velocity information (the array size is 0). So without the patch and without custom velocities, Cycles is just using an interpolation between the previous, current, and next frames.

Ah ok. Sorry then. I applied the patch but can't get Blender to build right now, or it crashes on startup. If I manage to build it, I'll test again. Thank you!

I managed to run a few tests and it works!