Sampling Subframes not working 2.8 #61432

New Issue

Remi · 2019-02-11T23:48:15+01:00

Remi commented

2019-02-11 23:48:15 +01:00

System Information
Operating system: centos
Graphics card:1080 ti

Blender Version
Broken: 2.8 8b192e1a6a

Short description of error
the Sampling Subframes in the flow smoke object setting doent seems to have any effect

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).
c-reate a smoke domaine from a default cube

create a smoke flow object from a default cube
create 3 key frame in translation
bake different simulation in point cache with different Sampling Subframes does not change anything in the result

**System Information** Operating system: centos Graphics card:1080 ti **Blender Version** Broken: 2.8 8b192e1a6a5f **Short description of error** the Sampling Subframes in the flow smoke object setting doent seems to have any effect **Exact steps for others to reproduce the error** Based on the default startup or an attached .blend file (as simple as possible). c-reate a smoke domaine from a default cube - create a smoke flow object from a default cube - create 3 key frame in translation - bake different simulation in point cache with different Sampling Subframes does not change anything in the result ![Capture du 2019-02-11 17-43-38.png](https://archive.blender.org/developer/F6583318/Capture_du_2019-02-11_17-43-38.png)

Remi commented

2019-02-11 23:48:15 +01:00

Added subscriber: @rlarroque

blender-admin commented

2019-02-11 23:48:15 +01:00

#65840 was marked as duplicate of this issue

blender-admin commented

2019-02-11 23:48:15 +01:00

#64357 was marked as duplicate of this issue

blender-admin commented

2019-02-11 23:48:15 +01:00

#63420 was marked as duplicate of this issue

Jacques Lucke commented

2019-02-12 11:06:05 +01:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2019-02-12 11:06:05 +01:00

Please provide a simple .blend file that allows us to reproduce the bug more easily.

Remi commented

2019-02-12 15:07:20 +01:00

smooktest.blend here is a simpla example from an animated object in blender

[smooktest.blend](https://archive.blender.org/developer/F6590255/smooktest.blend) here is a simpla example from an animated object in blender

Brecht Van Lommel commented

2019-04-09 20:17:11 +02:00

Added subscriber: @SlyNine

Brecht Van Lommel commented

2019-05-09 11:20:42 +02:00

Added subscribers: @finnb, @StephenSwaney

Finn Bear commented

2019-05-09 23:08:12 +02:00

I need this unbroken now. My smoke flow, in an animation that is important to me, travels extremely fast and leaves completely disjointed smoke puffs in its path. Why did it get set to low priority? Did you think it will be difficult to fix?

Finn Bear commented

2019-05-09 23:52:24 +02:00

Looks like this isn't a bug. I found the following in /source/blender/blenkernel/intern/smoke.c line 3027 (after about an hour of searching)

/* Disable substeps for now, since it results in numerical instability */
totalSubsteps = 1.0f;

Does the comment still apply?

If so, how severe is it? Would it be better to cap substeps at a value like 5 or 10, rather than just 1? How long is "for now"?

Also, if you are disabling a feature, shouldn't you do it in the UI and not the kernel? That way, users wouldn't expect it to work.

@JacquesLucke

Looks like this isn't a bug. I found the following in /source/blender/blenkernel/intern/smoke.c line 3027 (after about an hour of searching) ``` ``` ``` /* Disable substeps for now, since it results in numerical instability */ totalSubsteps = 1.0f; ``` Does the comment still apply? If so, how severe is it? Would it be better to cap substeps at a value like 5 or 10, rather than just 1? How long is "for now"? Also, if you are disabling a feature, shouldn't you do it in the UI and not the kernel? That way, users wouldn't expect it to work. @JacquesLucke

Joao Morgado commented

2019-05-13 19:02:33 +02:00

Added subscriber: @MrJoMo

Joao Morgado commented

2019-05-13 19:03:42 +02:00

Any news on this? I'm also working on a simulation that requires subframe sampling and it would be great for this to work.

SlyNine commented

2019-05-14 01:45:22 +02:00

You can create a smoke sim in 2.79 and import it I believe. It's worth a try at least. The point data shouldn't care after it's already baked.

Joao Morgado commented

2019-05-14 01:53:32 +02:00

You are correct. It is possible to bring it from 2.79. That's what I'm doing now, but it's a much slower (and limited) workflow.

Finn Bear commented

2019-05-14 03:55:51 +02:00

For me, I can't use 2.79 because the smoke flow object was created and edited in 2.8 only. The workflow would be a mess. Wouldn't it be better to remove the "totalSubsteps = 1.0f;" and let people use substeps at their own risk?

Finn Bear commented

2019-05-15 06:09:55 +02:00

Actually, you were right SlyNine. I was able to append the the smoke objects from the 2.8 blend file, bake the simulation in 2.79, and import it back. Still, is this bug/kludge ever going to get fixed?

Sebastian Parborg commented

2019-06-20 15:48:28 +02:00

Added subscriber: @stuntman7545

Joao Morgado commented

2019-07-05 19:05:00 +02:00

Added subscribers: @dfelinto, @brecht, @Ton

Joao Morgado commented

2019-07-05 19:05:00 +02:00

Hi @brecht and @JacquesLucke

I know the dev team is busy getting 2.8 ready for launch and I don't mean to nag you guys about this. But I'm a little worried this might have been forgotten. With the release candidate around the corner I would like to see this bug being addressed. As it is, it makes it pretty hard to use the smoke simulator in production with any kind of fast moving objects.

I know you are probably looking to replace the whole smoke simulator with the Mantaflow branch, but if that is not going to happen before the 2.8 release, then this should probably get at least back to how it worked in 2.79.

Would it help to bring this up to @dfelinto or @Ton attention? Do you need any more test files?
I'm not a developer, so I can't help much with the code, but I'm happy to help with anything else I can. Just let me know.

Hi @brecht and @JacquesLucke I know the dev team is busy getting 2.8 ready for launch and I don't mean to nag you guys about this. But I'm a little worried this might have been forgotten. With the release candidate around the corner I would like to see this bug being addressed. As it is, it makes it pretty hard to use the smoke simulator in production with any kind of fast moving objects. I know you are probably looking to replace the whole smoke simulator with the Mantaflow branch, but if that is not going to happen before the 2.8 release, then this should probably get at least back to how it worked in 2.79. Would it help to bring this up to @dfelinto or @Ton attention? Do you need any more test files? I'm not a developer, so I can't help much with the code, but I'm happy to help with anything else I can. Just let me know.

Brecht Van Lommel commented

2019-07-05 19:06:20 +02:00

This is not going to be fixed for 2.80, sorry, there is no time for it.

Joao Morgado commented

2019-07-05 19:56:17 +02:00

Thanks for the quick reply @brecht.

I understand we're so close to launch that it's too late to fix.
Would re-enabling the line @finnb mentioned be that unstable? (/source/blender/blenkernel/intern/smoke.c line 3027). It seemed to work in 2.79.

If not, I suggest the control being removed. As it is, we have a control in the flow options that doesn't do anything.

Thanks again for the all the great work on 2.8 and I look forward to seeing this bug fixed after the release so I can leave 2.79 behind.

Thanks for the quick reply @brecht. I understand we're so close to launch that it's too late to fix. Would re-enabling the line @finnb mentioned be that unstable? (/source/blender/blenkernel/intern/smoke.c line 3027). It seemed to work in 2.79. If not, I suggest the control being removed. As it is, we have a control in the flow options that doesn't do anything. Thanks again for the all the great work on 2.8 and I look forward to seeing this bug fixed after the release so I can leave 2.79 behind.

Joao Morgado commented

2019-07-20 15:25:06 +02:00

Any plans for this to be fixed before the final since the launch has been delayed with RC2?

Stephen Hamacek commented

2019-08-12 04:11:52 +02:00

Added subscriber: @StephenHamacek

Stephen Hamacek commented

2019-08-12 04:11:52 +02:00

Glad to find this report, Having this issue on Mac OS 2.80, and also keen for a fix. Keep up the fine work!

Alexander Kosenkov commented

2019-09-25 14:12:54 +02:00

Added subscriber: @alexkoskos

Alexander Kosenkov commented

2019-09-25 14:12:54 +02:00

Subframes still not working

Blender 2.80.75

Subframes still not working Blender 2.80.75

Johan Walles commented

2019-09-30 11:09:53 +02:00

Added subscriber: @Walles

Johan Walles commented

2019-09-30 14:47:16 +02:00

From https://www.blendernation.com/2019/09/24/developer-meeting-notes-september-23-2019/:

Mantaflow is being worked on with 2.82 in mind

And Blender 2.82 is scheduled for February 13 2020 .

So FWIW February 13 would be the timeline for Mantaflow to come to the rescue here.

And I'm not suggesting either waiting or fixing, I just wanted to add this datapoint since Mantaflow was mentioned.

From https://www.blendernation.com/2019/09/24/developer-meeting-notes-september-23-2019/: > Mantaflow is being worked on with 2.82 in mind And Blender 2.82 is [scheduled for February 13 2020 ](https://developer.blender.org/project/view/89/). So FWIW February 13 would be the timeline for Mantaflow to come to the rescue here. And I'm not suggesting either waiting or fixing, I just wanted to add this datapoint since Mantaflow was mentioned.

Johan Walles commented

2019-09-30 15:38:22 +02:00

Note also @finnb that the "Disable substeps for now" comment seems to be a red herring; it was in 2.79 as well...
https://developer.blender.org/rB1e13168183361e65e01c7613f094407780d0967e

... and @MrJoMo says above that 2.79 works.

Note also @finnb that the "Disable substeps for now" comment seems to be a red herring; it was in 2.79 as well... https://developer.blender.org/rB1e13168183361e65e01c7613f094407780d0967e ... and @MrJoMo says above that 2.79 works.

Johan Walles commented

2019-09-30 22:04:10 +02:00

One workaround that I was able to use with vanilla 2.8 was to:

Up the global Frame Rate in the Output section from 24fps to 100fps.
Multiply smoke Dissolve Time by 4 (I don't have "Slow" checked, not sure how Slow would affect this).
Multiply the Smoke Cache End frame by 4.
Render image 73 rather than image 19 (I tried 19*4=76 first, but 73 just happened to look better than 76)

In my case I'm not after an animation, but just a still of the smoke after it has developed.

Not sure how this would work for somebody who wants an animation of the smoke as it moves.

One workaround that I was able to use with vanilla 2.8 was to: * Up the global Frame Rate in the Output section from 24fps to 100fps. * Multiply smoke Dissolve Time by 4 (I don't have "Slow" checked, not sure how Slow would affect this). * Multiply the Smoke Cache End frame by 4. * Render image 73 rather than image 19 (I tried 19*4=76 first, but 73 just happened to look better than 76) In my case I'm not after an animation, but just a still of the smoke after it has developed. Not sure how this would work for somebody who wants an animation of the smoke as it moves.

Joao Morgado commented

2019-09-30 22:09:43 +02:00

Question for the devs. Is there a reason why we can't revert back to 2.79's behaviour. I understand that there are some bugs in it, but for the most part it was working in 2.79. Now there's features we can't even use.
Can we just bring back the old behaviour, even with the bugs, until we get MantaFlow? Maybe it's set as an "experimental feature" .

Question for the devs. Is there a reason why we can't revert back to 2.79's behaviour. I understand that there are some bugs in it, but for the most part it was working in 2.79. Now there's features we can't even use. Can we just bring back the old behaviour, even with the bugs, until we get MantaFlow? Maybe it's set as an "experimental feature" .

Andrew Price commented

2019-10-09 05:45:14 +02:00

Added subscriber: @AndrewPrice

Andrew Price commented

2019-10-09 05:45:14 +02:00

Is there really no faster timeline for this?

Subframes are crucial for smoke simulations, which make them basically unusable until this is fixed.

Feb 2020 is a long time, and MantaFlow is such a complex project it could be delayed even further. There's no faster fix?

Is there really no faster timeline for this? Subframes are crucial for smoke simulations, which make them basically unusable until this is fixed. Feb 2020 is a long time, and MantaFlow is such a complex project it could be delayed even further. There's no faster fix?

Sebastian Villanueva commented

2019-10-09 07:02:34 +02:00

Added subscriber: @vr_sebas

blender-admin commented

2019-10-09 15:00:25 +02:00

This issue was referenced by 6c9178b183

This issue was referenced by 6c9178b183f5267e07a6c55497b6d496e468a709

Sebastián Barschkis commented

2019-10-09 15:02:14 +02:00

Added subscriber: @sebbas

Sebastián Barschkis commented

2019-10-09 15:02:14 +02:00

Hi everyone! Dalai just showed me this task and I gave it a try. Found the problem and here is how it looks now:

The subframes had simply been disabled in the code. I am just going to push this to master since there's no way to make it worse.

Hi everyone! Dalai just showed me this task and I gave it a try. Found the problem and here is how it looks now: ![#61432.png](https://archive.blender.org/developer/F7798785/T61432.png) The subframes had simply been disabled in the code. I am just going to push this to master since there's no way to make it worse.

Sebastián Barschkis commented

2019-10-09 15:04:23 +02:00

Changed status from 'Open' to: 'Resolved'

Sebastián Barschkis closed this issue

2019-10-09 15:04:23 +02:00

Sebastián Barschkis self-assigned this 2019-10-09 15:04:23 +02:00

Joao Morgado commented

2019-10-09 15:11:29 +02:00

Thanks Sebastián. This is great! There's probably still some problems, but at least this makes the smoke simulator usable again until MantaFlow comes out.

Johan Walles commented

2019-10-09 15:31:35 +02:00

@sebbas, will this change be in 2.81?

Johan Walles commented

2019-10-09 15:35:06 +02:00

And for context, here's where it was disabled: https://developer.blender.org/rB4494be513ac455b106b2cb9be119136a58212cd1

Comment says:

Fix smoke to render in Cycles again.

Viewport caching seems still broken, though baking works.

Note that the disabling change contained a lot more changes than just the subframes disabling, so that comment may or may not be relevant in here.

And for context, here's where it was disabled: https://developer.blender.org/rB4494be513ac455b106b2cb9be119136a58212cd1 Comment says: > Fix smoke to render in Cycles again. > > Viewport caching seems still broken, though baking works. Note that the disabling change contained a lot more changes than just the subframes disabling, so that comment may or may not be relevant in here.

Sebastián Barschkis commented

2019-10-09 15:50:10 +02:00

@Walles I would say so as today is still part of bcon2 (on master)

Johan Walles commented

2019-10-10 09:26:09 +02:00

Awesome timing @sebbas :)

Sebastian Villanueva commented

2019-10-10 21:50:21 +02:00

This is great! ? Thanks @sebbas

Alexander Kosenkov commented

2019-10-10 22:04:11 +02:00

Now works great in 2.81, but not working when using particles for emitting smoke :(

Joseph Hamilton commented

2019-10-22 06:12:03 +02:00

In #61432#793623, @alexkoskos wrote:
Now works great in 2.81, but not working when using particles for emitting smoke :(

Yes unfortunately the subframe sampling is still not working for particle systems emitting smoke. Still unusable as of right now.

Sucks because even the render preview of smoke and fire in Blender 2.8 looks so much better but this one issue makes me go back to 2.79 for simulation :(

> In #61432#793623, @alexkoskos wrote: > Now works great in 2.81, but not working when using particles for emitting smoke :( Yes unfortunately the subframe sampling is still not working for particle systems emitting smoke. Still unusable as of right now. Sucks because even the render preview of smoke and fire in Blender 2.8 looks so much better but this one issue makes me go back to 2.79 for simulation :(

Andrew Price commented

2019-10-22 08:16:47 +02:00

Thanks for the quick fix on the smoke @sebbas.

But as others have said, the particle subframe sampling is still broken. Is this an easy fix?

Thanks for the quick fix on the smoke @sebbas. But as others have said, the particle subframe sampling is still broken. Is this an easy fix? ![blender_2019-10-22_16-15-26.png](https://archive.blender.org/developer/F7846316/blender_2019-10-22_16-15-26.png)

Sebastián Barschkis commented

2019-11-07 21:51:55 +01:00

@AndrewPrice Yes, it was a fairly small fix. Just committed it and so it will be part of 2.81.

Luja Rajbhandari commented

2020-02-13 15:00:40 +01:00

Added subscriber: @LujaRajbhandari

Luja Rajbhandari commented

2020-02-13 15:00:40 +01:00

Particle subframe sampling is still broken in 2.81 when the emitter is parented to a moving object with the child of constraint. I guess its the constraint problem. Nonetheless, it should be fixed.

Loïc DAUTRY commented

2020-04-14 16:11:02 +02:00

Added subscriber: @L0Lock

Loïc DAUTRY commented

2020-04-14 16:11:02 +02:00

Broken on modifiers as of today. On 2.82 stable, even simple parents couldn't do it. I've tried to get it working with 2.83 daily builds for weeks, in which more situations do work, but it fails with modifiers, the most important one in my eyes being the armature modifier :

substeps_broken.blend

Broken on modifiers as of today. On 2.82 stable, even simple parents couldn't do it. I've tried to get it working with 2.83 daily builds for weeks, in which more situations do work, but it fails with modifiers, the most important one in my eyes being the armature modifier : ![image.png](https://archive.blender.org/developer/F8471349/image.png) [substeps_broken.blend](https://archive.blender.org/developer/F8471353/substeps_broken.blend)

Brecht Van Lommel commented

2020-04-14 16:15:50 +02:00

Please make a new bug report, we don't reopen old reports.

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Sampling Subframes not working 2.8 #61432