fluid simulation: generate mesh bug #50887

New Issue

Pavel Blend · 2017-03-08T12:13:42+01:00

Pavel Blend commented

2017-03-08 12:13:42 +01:00

System Information
Windows 7 64 bit, CPU: AMD A8-5600K APU with Radeon HD Graphics, GPU: None, Ram: 8 GB.

Blender Version
Broken: 2.78c e92f235283

Short description of error
In fluid simulation, I found an error when generating a mesh. A mesh of liquid is not completely created, there are holes that are not filled with polygons. Because of this, the mesh is not a Non-Manifold geometry. Holes appear in random places. There is no regularity. Sometimes a mesh is generated as a whole. And it is difficult to reproduce this bug.

Here is an example error:
YouTube Vodeo

Exact steps for others to reproduce the error
Here is the scene with an error (the liquid is not baked):
fluid_generate_mesh_bug.zip

**System Information** Windows 7 64 bit, CPU: AMD A8-5600K APU with Radeon HD Graphics, GPU: None, Ram: 8 GB. **Blender Version** Broken: 2.78c e92f235283 **Short description of error** In fluid simulation, I found an error when generating a mesh. A mesh of liquid is not completely created, there are holes that are not filled with polygons. Because of this, the mesh is not a Non-Manifold geometry. Holes appear in random places. There is no regularity. Sometimes a mesh is generated as a whole. And it is difficult to reproduce this bug. Here is an example error: [YouTube Vodeo](https://www.youtube.com/watch?v=ZHJbjQ5xYTU&feature=youtu.be) **Exact steps for others to reproduce the error** Here is the scene with an error (the liquid is not baked): [fluid_generate_mesh_bug.zip](https://archive.blender.org/developer/F505406/fluid_generate_mesh_bug.zip)

Pavel Blend commented

2017-03-08 12:13:42 +01:00

Changed status to: 'Open'

Pavel Blend commented

2017-03-08 12:13:42 +01:00

Added subscriber: @Pavel_Blend

Krzysztof Rećko commented

2017-03-08 21:05:12 +01:00

Added subscriber: @chrisr

Krzysztof Rećko commented

2017-03-09 10:26:56 +01:00

Could this be an effect of "Remove air bubbles" option (under "Fluid boundary")?

EDIT: Did more tests, holes are still there with this option OFF... It's a dead end.

Could this be an effect of "Remove air bubbles" option (under "Fluid boundary")? EDIT: Did more tests, holes are still there with this option OFF... It's a dead end.

Krzysztof Rećko commented

2017-03-11 03:56:10 +01:00

OK. So. Managed to reproduce this. Does appear to be connected to Fluid boundary -> Surface -> Smoothing option, but only appears at higher resolutions which makes it a pain to debug.

Resolution	Smooth	Remove Air Bubbles	Holes?
200	3	No	No
100	1	No	No
100	3	Yes	No
250	0	No	No
250	0	Yes	No
160	0	No	No
250	3	Yes	Yes
250	3	No	Yes
250	1	Yes	Yes
250	1	No	Yes
160	1	No	Yes

Grabbing this for myself for now.

OK. So. Managed to reproduce this. Does appear to be connected to *Fluid boundary -> Surface -> Smoothing* option, but only appears at higher resolutions which makes it a pain to debug. ![hole2.PNG](https://archive.blender.org/developer/F506769/hole2.PNG) ![hole1.PNG](https://archive.blender.org/developer/F506768/hole1.PNG) | Resolution | Smooth | Remove Air Bubbles | Holes? | | ---- | ---- | ---- | ---- | | 200 | 3 | No | No | | 100 | 1 | No | No | | 100 | 3 | Yes | No | | 250 | 0 | No | No | | 250 | 0 | Yes | No | | 160 | 0 | No | No | | 250 | 3 | Yes | Yes | | 250 | 3 | No | Yes | | 250 | 1 | Yes | Yes | | 250 | 1 | No | Yes | | 160 | 1 | No | Yes | Grabbing this for myself for now.

Krzysztof Rećko self-assigned this 2017-03-11 03:57:21 +01:00

Acorn Bits commented

2017-06-24 21:36:14 +02:00

Added subscriber: @AcornBits

Acorn Bits commented

2017-06-24 21:58:38 +02:00

It is happening for us all the time, in more than 10 frames out of 180 of a simulation (resolution 550, smoothing 1, remove air bubbles Yes, speed 0.8).

However, there is something else which makes this bug even more troublesome: Cycles does not render properly the mesh if there is a hole. Only one "half" of the mesh is rendered; while the other "half" on the other side of the hole is completely discarded (i.e. as if it was not there to begin with). It only happens, however, if the hole it visible to the camera/scene: if you make the hole out of sight from the camera, both sides are rendered just fine. So it would seem to be not a problem with the entire mesh, but rather something that is only triggered depending on whether the hole actually can be seen in the frame. We point this out because, as far as we know, Cycles can render non-manifold meshes. Seeing the related change in D2556, is it maybe related to the fact that some numbers/areas are infinite/NaN and Cycles in that case stops handling the mesh properly?

Since modifiers can be applied to the cached fluid mesh, one "workaround" we found (for the Cycles issue) is, for instance, using the Remesh modifier with high depth. Maybe it helps somebody out there.

Thank you for taking time looking into this.

It is happening for us all the time, in more than 10 frames out of 180 of a simulation (resolution 550, smoothing 1, remove air bubbles Yes, speed 0.8). However, there is something else which makes this bug even more troublesome: Cycles does not render properly the mesh if there is a hole. Only one "half" of the mesh is rendered; while the other "half" on the other side of the hole is completely discarded (i.e. as if it was not there to begin with). It only happens, however, if the hole it visible to the camera/scene: if you make the hole out of sight from the camera, both sides are rendered just fine. So it would seem to be not a problem with the entire mesh, but rather something that is only triggered depending on whether the hole actually can be seen in the frame. We point this out because, as far as we know, Cycles can render non-manifold meshes. Seeing the related change in [D2556](https://archive.blender.org/developer/D2556), is it maybe related to the fact that some numbers/areas are infinite/NaN and Cycles in that case stops handling the mesh properly? Since modifiers can be applied to the cached fluid mesh, one "workaround" we found (for the Cycles issue) is, for instance, using the Remesh modifier with high depth. Maybe it helps somebody out there. Thank you for taking time looking into this.

blender-admin commented

2017-06-30 03:30:15 +02:00

This issue was referenced by 9c2bbfb6ce

This issue was referenced by 9c2bbfb6ce90007a11f0fc4b2a1afa7d2eab5039

Campbell Barton commented

2017-06-30 03:41:38 +02:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2017-06-30 03:41:38 +02:00

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Resolution	Smooth	Remove Air Bubbles	Holes?
200	3	No	No
100	1	No	No
100	3	Yes	No
250	0	No	No
250	0	Yes	No
160	0	No	No
250	3	Yes	Yes
250	3	No	Yes
250	1	Yes	Yes
250	1	No	Yes
160	1	No	Yes

Resolution	Smooth	Remove Air Bubbles	Holes?
200	3	No	No
100	1	No	No
100	3	Yes	No
250	0	No	No
250	0	Yes	No
160	0	No	No
250	3	Yes	Yes
250	3	No	Yes
250	1	Yes	Yes
250	1	No	Yes
160	1	No	Yes

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fluid simulation: generate mesh bug #50887

Resolution	Smooth	Remove Air Bubbles	Holes?
200	3	No	No
100	1	No	No
100	3	Yes	No
250	0	No	No
250	0	Yes	No
160	0	No	No
250	3	Yes	Yes
250	3	No	Yes
250	1	Yes	Yes
250	1	No	Yes
160	1	No	Yes