Mantaflow: Effect of forces increases over time. #73837

New Issue

Iago Mota · 2020-02-15T14:36:07+01:00

Iago Mota commented

2020-02-15 14:36:07 +01:00

System Information
Operating system: Windows 10
Graphics card: Nvidia GeForce GTX 650 Ti
Processor: Intel® Core™ i7-3770

Blender Version
Broken: 2.82, master. (this is a general problem with Mantaflow; previous versions of Blender with Mantaflow implementation also possess this problem)
Worked: (previous gas simulation framework)

Short description of error
The effects of external forces on smoke (vorticity, force-fields, etc.) seem to increase in strength over time, despite not being animated. I am not sure if this is intended behavior; however, it certainly hinders the use of Mantaflow and I believe it should be minimized.

Demo with vorticity. (I am using a very medium strength for vorticity. This problem becomes much more dramatic, when using greater values, such as 1.0)
C-Increasing Force Strength - Demo1.mp4
Demo with a "Force" force-field.
C-Increasing Force Strength - Demo2.mp4

Exact steps for others to reproduce the error

Add a mesh.
Press F3, type in and select "Quick Smoke"
In domain settings, set vorticity to a medium value (ie: 0.3; 0.5; etc.)
Bake the simulation.

Here are two .blend files, one with just the vorticity changes and one with a force field:
BugReport_01_increasing_force_strength.blend

BugReport_01_increasing_force_strength_2.blend

**System Information** Operating system: Windows 10 Graphics card: Nvidia GeForce GTX 650 Ti Processor: Intel® Core™ i7-3770 **Blender Version** Broken: 2.82, master. (this is a general problem with Mantaflow; previous versions of Blender with Mantaflow implementation also possess this problem) Worked: (previous gas simulation framework) **Short description of error** The effects of external forces on smoke (vorticity, force-fields, etc.) seem to increase in strength over time, despite not being animated. I am not sure if this is intended behavior; however, it certainly hinders the use of Mantaflow and I believe it should be minimized. Demo with vorticity. (I am using a very medium strength for vorticity. This problem becomes much more dramatic, when using greater values, such as 1.0) [C-Increasing Force Strength - Demo1.mp4](https://archive.blender.org/developer/F8341209/C-Increasing_Force_Strength_-_Demo1.mp4) Demo with a "Force" force-field. [C-Increasing Force Strength - Demo2.mp4](https://archive.blender.org/developer/F8341208/C-Increasing_Force_Strength_-_Demo2.mp4) **Exact steps for others to reproduce the error** 1. Add a mesh. 2. Press F3, type in and select "Quick Smoke" 3. In domain settings, set vorticity to a medium value (ie: 0.3; 0.5; etc.) 4. Bake the simulation. Here are two .blend files, one with just the vorticity changes and one with a force field: [BugReport_01_increasing_force_strength.blend](https://archive.blender.org/developer/F8341215/BugReport_01_increasing_force_strength.blend) [BugReport_01_increasing_force_strength_2.blend](https://archive.blender.org/developer/F8341214/BugReport_01_increasing_force_strength_2.blend)

Iago Mota commented

2020-02-15 14:36:07 +01:00

Added subscriber: @Iago-Diogo-de-Vasconcelos-Mota

Evan Wilson commented

2020-02-15 16:24:47 +01:00

Added subscriber: @EAW

Evan Wilson commented

2020-02-15 16:24:47 +01:00

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

Evan Wilson commented

2020-02-15 16:24:47 +01:00

Confirmed using 2.82 release

Silas Opel commented

2020-02-15 17:21:05 +01:00

Added subscriber: @DarkKnight

Sebastián Barschkis was assigned by Bastien Montagne

2020-02-17 15:25:37 +01:00

Seth commented

2020-02-19 17:51:30 +01:00

Added subscriber: @VirtusH

Everton Schneider commented

2020-05-13 16:43:02 +02:00

Added subscriber: @EvertonSchneider

Everton Schneider commented

2020-05-13 16:43:02 +02:00

This bug seem to be squashed to me.. I tested the attached files and they are working fine to me. Can you confirm this @Iago-Diogo-de-Vasconcelos-Mota ?

Iago Mota commented

2020-05-13 18:19:35 +02:00

@EvertonSchneider That's strange. I just tested in 2.83 50ef801a79, the issues still persist there.

@EvertonSchneider That's strange. I just tested in 2.83 50ef801a79b5, the issues still persist there.

Everton Schneider commented

2020-05-14 15:20:41 +02:00

@Iago-Diogo-de-Vasconcelos-Mota I'm testing here with current Master (2.90 alpha) didn't test with 2.83.
With 2.90 alpha the only thing that still happens is the vorticity spreading the smoke, but I'm not sure if this is the correct behavior, maybe this is the way it works and we need to keep really low values, I think it is very exaggerated with 0.3 but not sure...
2020-05-14 10-13-00.mp4
The force field example is working fine to me. The smoke is immediately influenced by the force.
2020-05-14 10-14-52.mp4

@Iago-Diogo-de-Vasconcelos-Mota I'm testing here with current Master (2.90 alpha) didn't test with 2.83. With 2.90 alpha the only thing that still happens is the vorticity spreading the smoke, but I'm not sure if this is the correct behavior, maybe this is the way it works and we need to keep really low values, I think it is very exaggerated with 0.3 but not sure... [2020-05-14 10-13-00.mp4](https://archive.blender.org/developer/F8535274/2020-05-14_10-13-00.mp4) The force field example is working fine to me. The smoke is immediately influenced by the force. [2020-05-14 10-14-52.mp4](https://archive.blender.org/developer/F8535280/2020-05-14_10-14-52.mp4)

Iago Mota commented

2020-05-16 05:16:42 +02:00

@EvertonSchneider You're right, 2.90 alpha seems to have the issue fixed with force fields. If smoke/flame Vorticity are the only properties influenced by this bug, it's probably not significant anymore, in my opinion. So, I'm glad to see this pretty much resolved!

Jacques Lucke commented

2020-06-03 16:31:48 +02:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2020-06-03 16:31:48 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Jacques Lucke closed this issue

2020-06-03 16:31:48 +02:00

Jacques Lucke commented

2020-06-03 16:31:48 +02:00

Looks like this has been solved in 21485e94aa.
The vorticity thing seems to be a separate issue, I'm not sure if it is a bug. If you think it is, please create a new report just for that. Reusing the same report for two bugs makes things hard to follow.

Looks like this has been solved in 21485e94aa. The vorticity thing seems to be a separate issue, I'm not sure if it is a bug. If you think it is, please create a new report just for that. Reusing the same report for two bugs makes things hard to follow.

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Mantaflow: Effect of forces increases over time. #73837