Mantaflow liquid sim mesh won't have speed vectors with OpenVDB as cache method #81202

New Issue

Juan Gea · 2020-09-26T11:45:45+02:00

Juan Gea commented

2020-09-26 11:45:45 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.38

Blender Version
Broken: version: 2.91.0 Alpha, branch: boneMaster291, commit date: 2020-09-22 14:52, hash: 081850b220

It's our own build, but it's basically the same as master as we have not touched a single thing related to all this.

Short description of error
That's the description, if we use OpenVDB as cache method for liquids the mesh won't have any speed vectors as a result, if we use UniCache it will have vectors information.

Exact steps for others to reproduce the error
1.- Open the example file
2.- Go to the Liquid Domain object, and there to the mantaflow settings tab
3.- Go to the cache section and ensure you have OpenVDB as cache format, and All as cache type, just for the shake of simplicity.
4.- Press bake
5.- in frame 18 press F12 to render
6.- the result won't have motion blur
7.- Repeat step 3, but now configure UniCache as cache format
8.- press bake
9.- in frame 18 press F12 to render
10.- you will see motion blur in the render

Here is also a video showing the problem:
manta_openvdb_vectors_bug.mp4

And here is the sample file:
test_speed_vectors.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.38 **Blender Version** Broken: version: 2.91.0 Alpha, branch: boneMaster291, commit date: 2020-09-22 14:52, hash: `081850b220` It's our own build, but it's basically the same as master as we have not touched a single thing related to all this. **Short description of error** That's the description, if we use OpenVDB as cache method for liquids the mesh won't have any speed vectors as a result, if we use UniCache it will have vectors information. **Exact steps for others to reproduce the error** 1.- Open the example file 2.- Go to the Liquid Domain object, and there to the mantaflow settings tab 3.- Go to the cache section and ensure you have OpenVDB as cache format, and All as cache type, just for the shake of simplicity. 4.- Press bake 5.- in frame 18 press F12 to render 6.- the result won't have motion blur 7.- Repeat step 3, but now configure UniCache as cache format 8.- press bake 9.- in frame 18 press F12 to render 10.- you will see motion blur in the render Here is also a video showing the problem: [manta_openvdb_vectors_bug.mp4](https://archive.blender.org/developer/F8924114/manta_openvdb_vectors_bug.mp4) And here is the sample file: [test_speed_vectors.blend](https://archive.blender.org/developer/F8924123/test_speed_vectors.blend)

Juan Gea commented

2020-09-26 11:45:45 +02:00

Added subscriber: @juang3d

Stefano Lazzaroni commented

2020-09-27 13:41:05 +02:00

Added subscribers: @sebbas, @Lazza

Stefano Lazzaroni commented

2020-09-27 13:41:05 +02:00

In #78442#982856, @sebbas wrote:
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.

Motion blur with OpenVDB isn't working because it is not implemented.

> In #78442#982856, @sebbas wrote: > 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. Motion blur with OpenVDB isn't working because it is not implemented.

Juan Gea commented

2020-09-27 15:30:31 +02:00

I thought that was for smoke, not for liquid.

However if that's the case, a warning should appear below the "calculate speed vectors" checkbox when openVDB is the cache method, because right now it's not obvious :)

I thought that was for smoke, not for liquid. However if that's the case, a warning should appear below the "calculate speed vectors" checkbox when openVDB is the cache method, because right now it's not obvious :)

Richard Antalik commented

2020-10-01 17:30:34 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-10-01 17:30:34 +02:00

I will merge this into #78442 because it is technically same issue.

Richard Antalik commented

2020-10-01 17:30:44 +02:00

Closed as duplicate of #78442

Richard Antalik closed this issue

2020-10-01 17:30:44 +02:00

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Mantaflow liquid sim mesh won't have speed vectors with OpenVDB as cache method #81202