Mantaflow: motion blur does not work on liquids cached with OpenVDB format #78442

New Issue

Steffen Dünner · 2020-06-29T19:34:05+02:00

Steffen Dünner commented

2020-06-29 19:34:05 +02:00

System Information
Operating system: Linux-5.4.45-050445-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.36.06

Blender Version
Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-29 16:20, hash: 5d31ef0820
Worked: 2.83.1

Short description of error
A FLIP fluid mesh no renders with motion blur in Cycles (despite the "Use Speed Vectors" option is checked) when OpenVDB cache is used.

Exact steps for others to reproduce the error

Open the attached blend file or create a super simple scene yourself by:

- add a cube as a fluid domain,
- add another cube inside it as inflow.
- Set both to be of fluid type.
- Under the "Mesh" options check "Use Speed Vectors"
- Activate motion blur in Cycles.
- Set cache type to OpenVDB

Go to frame 20 (where the falling liquid should show motion blur) and press F12
No motion blur
This exact workflow rendered with motion blur in 2.83.1 official
Eevee also doesn't show motion blur
If I open the cached VDB sequence in Houdini I can see a velocity field and vdb particles containing motion blur vectors.

Mantaflow_MB_Bug_v01.blend

**System Information** Operating system: Linux-5.4.45-050445-generic-x86_64-with-debian-buster-sid 64 Bits Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.36.06 **Blender Version** Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-29 16:20, hash: `5d31ef0820` Worked: 2.83.1 **Short description of error** A FLIP fluid mesh no renders with motion blur in Cycles (despite the "Use Speed Vectors" option is checked) when OpenVDB cache is used. ![image.png](https://archive.blender.org/developer/F8653966/image.png) **Exact steps for others to reproduce the error** - Open the attached blend file or create a super simple scene yourself by: ``` - add a cube as a fluid domain, - add another cube inside it as inflow. - Set both to be of fluid type. - Under the "Mesh" options check "Use Speed Vectors" - Activate motion blur in Cycles. - Set cache type to OpenVDB ``` - Go to frame 20 (where the falling liquid should show motion blur) and press F12 No motion blur This exact workflow rendered with motion blur in 2.83.1 official Eevee also doesn't show motion blur If I open the cached VDB sequence in Houdini I can see a velocity field and vdb particles containing motion blur vectors. [Mantaflow_MB_Bug_v01.blend](https://archive.blender.org/developer/F8653968/Mantaflow_MB_Bug_v01.blend)

Steffen Dünner commented

2020-06-29 19:34:05 +02:00

Added subscriber: @SteffenD

blender-admin commented

2020-06-29 19:34:05 +02:00

#91365 was marked as duplicate of this issue

blender-admin commented

2020-06-29 19:34:05 +02:00

#81654 was marked as duplicate of this issue

blender-admin commented

2020-06-29 19:34:05 +02:00

#81202 was marked as duplicate of this issue

Germano Cavalcante commented

2020-06-30 16:07:16 +02:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-06-30 16:07:16 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Germano Cavalcante commented

2020-06-30 16:07:17 +02:00

I cannot reproduce this with the current development versions of Blender: https://builder.blender.org/download/

See the blur at the bottom of the fluid:

In the file I had to choose a cache format, otherwise the simulation was not baked.

Go to File → Defaults → Load Factory Settings and then load your file to see if you still can reproduce this issue.

I cannot reproduce this with the current development versions of Blender: https://builder.blender.org/download/ See the blur at the bottom of the fluid: ![fluid_sim_result.png](https://archive.blender.org/developer/F8655313/fluid_sim_result.png) In the file I had to choose a cache format, otherwise the simulation was not baked. Go to File → Defaults → Load Factory Settings and then load your file to see if you still can reproduce this issue.

Steffen Dünner commented

2020-06-30 16:27:41 +02:00

Thanks for investigating.

I can reproduce the problem with both, my own compile of master and the very latest buildbot build (both on Linux).
Loading factory defaults doesn't help, caching to VDBs doesn't help as well BUT caching to "Uni Cache" works, even when setting the mode to "Replay" to use the "live" version.
So it looks like a problem (Linux only?) that likely started to appear when Sebbas changed the VDB caching to cache multiple fields / grids?

Thanks for investigating. I can reproduce the problem with both, my own compile of master and the very latest buildbot build (both on Linux). Loading factory defaults doesn't help, caching to VDBs doesn't help as well BUT caching to "Uni Cache" works, even when setting the mode to "Replay" to use the "live" version. So it looks like a problem (Linux only?) that likely started to appear when Sebbas changed the VDB caching to cache multiple fields / grids?

Germano Cavalcante commented

2020-06-30 16:34:34 +02:00

Changed status from 'Needs User Info' to: 'Needs Triage'

Germano Cavalcante commented

2020-06-30 16:45:18 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Germano Cavalcante commented

2020-06-30 16:45:19 +02:00

I can confirm with OpenVDB.

Steffen Dünner commented

2020-06-30 16:48:40 +02:00

Nice! Good to hear that I'm not the only one ;)

Sebastián Barschkis commented

2020-07-21 15:42:25 +02:00

Added subscriber: @sebbas

Sebastián Barschkis commented

2020-07-21 15:42:25 +02:00

Small update: Since 6b6e2e742f motion blur works again when using "Uni" as the format for volumes. Motion blur support with OpenVDB remains to do.

EDIT: Motion blur with "Uni" caching seemed to work before too - in that case this was more of a clean up, e.g. the mesh file were written twice per frame under different names before.

Small update: Since 6b6e2e742ff4 motion blur works again when using "Uni" as the format for volumes. Motion blur support with OpenVDB remains to do. EDIT: Motion blur with "Uni" caching seemed to work before too - in that case this was more of a clean up, e.g. the mesh file were written twice per frame under different names before.

mantissa commented

2020-08-17 00:26:30 +02:00

Added subscriber: @Mantissa

Richard Antalik commented

2020-10-01 17:30:46 +02:00

Added subscribers: @juang3d, @iss, @Lazza

Germano Cavalcante changed title from ~~Mantaflow no longer renders motion blur~~ to Mantaflow: motion blur does not work on liquids cached with OpenVDB format

2020-10-13 23:15:17 +02:00

Germano Cavalcante commented

2020-10-13 23:23:17 +02:00

Added subscriber: @koko_ze

Jesse Yurkovich commented

2021-09-13 07:38:11 +02:00

Added subscribers: @Yerus_Ovelha, @deadpin

zebus3d commented

2021-12-07 23:50:20 +01:00

Added subscriber: @zebus3dream

Rowan Ibbeken commented

2022-04-03 10:27:34 +02:00

Added subscriber: @Rowan-Ibbeken

Rowan Ibbeken commented

2022-04-03 10:28:26 +02:00

Has there been any progress on enabling motion blur for Open VDB volumes/liquids?

Dalai Felinto commented

2022-05-09 11:02:08 +02:00

Mantaflow (fluid simulator) has no active developer at the moment. Moving those bugs as known issues so at least other users can find their issues already reported.

Rombout Versluijs commented

2022-05-27 18:54:06 +02:00

Added subscriber: @RomboutVersluijs

Rombout Versluijs commented

2022-05-27 18:54:06 +02:00

Aside from this, importing this ovb data results in nothing. I only see speed vectory and particles when i import the data.

Philipp Oeser removed the

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Mantaflow: motion blur does not work on liquids cached with OpenVDB format #78442