Mantaflow Liquid - Gravity not respecting Time Scale from domain. #76426

New Issue

Everton Schneider · 2020-05-05T02:36:34+02:00

Everton Schneider commented

2020-05-05 02:36:34 +02:00

System Information
Operating system: Linux-5.4.0-29-generic-x86_64-with-debian-bullseye-sid 64 Bits
Graphics card: GeForce RTX 2080 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.64

Blender Version
Broken: version: 2.90 (sub 0), branch: master, commit date: 2020-05-04 16:18, hash: 375a50dad9
Worked: (newest version of Blender that worked as expected)

Short description of error
It seems to me that gravity is not respecting the time scale setting from the liquid domain. The liquid is freezing but the gravity keeps acting over the fluid at the normal speed...

Exact steps for others to reproduce the error
Just playback the attached file and see what I mean. The time scale is animated from default 1.0 to 0.1.

Liquid_Gravity_TimeScale.blend

**System Information** Operating system: Linux-5.4.0-29-generic-x86_64-with-debian-bullseye-sid 64 Bits Graphics card: GeForce RTX 2080 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.64 **Blender Version** Broken: version: 2.90 (sub 0), branch: master, commit date: 2020-05-04 16:18, hash: `375a50dad9` Worked: (newest version of Blender that worked as expected) **Short description of error** It seems to me that gravity is not respecting the time scale setting from the liquid domain. The liquid is freezing but the gravity keeps acting over the fluid at the normal speed... ![ezgif.com-optimize.gif](https://archive.blender.org/developer/F8512910/ezgif.com-optimize.gif) **Exact steps for others to reproduce the error** Just playback the attached file and see what I mean. The time scale is animated from default 1.0 to 0.1. [Liquid_Gravity_TimeScale.blend](https://archive.blender.org/developer/F8512896/Liquid_Gravity_TimeScale.blend)

Everton Schneider commented

2020-05-05 02:36:34 +02:00

Added subscriber: @EvertonSchneider

Philipp Oeser commented

2020-05-05 10:58:44 +02:00

Added subscribers: @sebbas, @lichtwerk

Philipp Oeser commented

2020-05-05 10:58:44 +02:00

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

Philipp Oeser commented

2020-05-05 10:58:44 +02:00

Not sure how this is supposed to work (observed behavior seems unpredictable to me as well...)

@sebbas: mind checking? (will confirm for now...)

Not sure how this is supposed to work (observed behavior seems unpredictable to me as well...) @sebbas: mind checking? (will confirm for now...)

Everton Schneider commented

2020-05-06 05:06:07 +02:00

The expected behavior is the same as in the SPH Particles example here:

Note that the timestep starts with default value and is animated to a lower value, slowing down the particle simulation AND also takes into account the gravity and forces influences. Note that the velocity color of the particles doesn't change when the timestep is slowing down, the velocity remains the same but the timestep is slower...

The expected behavior is the same as in the SPH Particles example here: ![ezgif.com-optimize (1).gif](https://archive.blender.org/developer/F8515003/ezgif.com-optimize__1_.gif) Note that the timestep starts with default value and is animated to a lower value, slowing down the particle simulation AND also takes into account the gravity and forces influences. Note that the velocity color of the particles doesn't change when the timestep is slowing down, the velocity remains the same but the timestep is slower...

Everton Schneider commented

2020-05-06 05:12:18 +02:00

Force Fields are not working also...
Note in the attached file that right when the timestep is slowing down the liquid particles starts to go crazy, their velocity color goes red immediately...
The above mentioned SPH particles behavior takes into account the force fields and gravity as expected, keeping the motion of the particles and only slowing down the timestep.

Liquid_Gravity_TimeScale.blend

Force Fields are not working also... Note in the attached file that right when the timestep is slowing down the liquid particles starts to go crazy, their velocity color goes red immediately... The above mentioned SPH particles behavior takes into account the force fields and gravity as expected, keeping the motion of the particles and only slowing down the timestep. [Liquid_Gravity_TimeScale.blend](https://archive.blender.org/developer/F8515010/Liquid_Gravity_TimeScale.blend)

blender-admin commented

2020-05-07 17:15:15 +02:00

This issue was referenced by 6400f54b4c

This issue was referenced by 6400f54b4cc6d9cdb420ac4f62dd5eb0387aa7c0

Sebastián Barschkis commented

2020-05-07 17:35:09 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Sebastián Barschkis closed this issue

2020-05-07 17:35:09 +02:00

Sebastián Barschkis self-assigned this 2020-05-07 17:35:09 +02:00

Everton Schneider commented

2020-05-07 17:55:05 +02:00

Great work! Thank you SO MUCH! You are an awesome team! But special thanks to sebbas! Thank you! thank you! thank you!

Everton Schneider commented

2020-05-07 22:12:52 +02:00

Please, check the blend file attached in the comment that I said about Force Fields... after checking this problem with forcefields I see the same problem still happening...

Everton Schneider commented

2020-05-07 22:26:41 +02:00

Now there's an even stranger thing happening... see the attached file, please. Also, after checking the file please test the minimum timestep value of the domain, default is 1 change it to 4(same value as maximum) and the result seems to be slower with time scale 1...

Liquid_ForceFields_TimeScale.blend

Now there's an even stranger thing happening... see the attached file, please. Also, after checking the file please test the minimum timestep value of the domain, default is 1 change it to 4(same value as maximum) and the result seems to be slower with time scale 1... [Liquid_ForceFields_TimeScale.blend](https://archive.blender.org/developer/F8518892/Liquid_ForceFields_TimeScale.blend)

Everton Schneider commented

2020-05-08 16:31:04 +02:00

Thanks, @sebbas I just compiled blender now after your additional fix, and everything related to this report is working fine now! The slowdown in time scale is taking gravity and forcefields into account. THANK YOU!
There's something weird already with forcefields but I will open a separate report. The animated "Max Distance" under "Fallof" are affecting particles(SPH) and liquid(MANTAFLOW) even outside of radius scale, there's full influence inside the Max Distance radius but outside of the radius there's still a little of influence, it's not totally 0.

Thanks, @sebbas I just compiled blender now after your additional fix, and everything related to this report is working fine now! The slowdown in time scale is taking gravity and forcefields into account. THANK YOU! There's something weird already with forcefields but I will open a separate report. The animated "Max Distance" under "Fallof" are affecting particles(SPH) and liquid(MANTAFLOW) even outside of radius scale, there's full influence inside the Max Distance radius but outside of the radius there's still a little of influence, it's not totally 0.

Sebastián Barschkis commented

2020-05-08 17:48:14 +02:00

@EvertonSchneider Ok, great! Yes, a new report would appropriate for that!

john baker commented

2020-05-09 20:00:31 +02:00

Added subscriber: @jbaker8935

john baker commented

2020-05-09 20:00:31 +02:00

Is there a way to simulate the old behavior ? eg. divide gravity by the time scale? (edit: <= almost but not quite) to allow older blends to be edited in 2.9 without a complete rework.

e.g., this relied on the bug. https://www.youtube.com/watch?v=Rc5-R12XZFk

of course going forward i'll use the new behavior

Is there a way to simulate the old behavior ? eg. divide gravity by the time scale? (edit: <= almost but not quite) to allow older blends to be edited in 2.9 without a complete rework. e.g., this relied on the bug. https://www.youtube.com/watch?v=Rc5-R12XZFk of course going forward i'll use the new behavior

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Mantaflow Liquid - Gravity not respecting Time Scale from domain. #76426