Blender Foundation: Blender 2.x BF release: Detail: 21630 Smoke Sim's heat value changes by itself

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[#21630] Smoke Sim's heat value changes by itself

Date:
2010-03-16 04:03 Priority:
3

State:
Closed

Submitted by:
David Tilman (davidt) Assigned to:
Daniel Genrich (genscher)

Category:
Physics Status:
Fixed / Closed

Relates to: Duplicates:

Patches:

Summary:
Smoke Sim's heat value changes by itself

Detailed description

I have created smoke simulations where the heat difference is set so the smoke should not rise or lower. It is then moved in a horizontal direction by a wind effector. Eventually the smoke will start rising fairly quickly, but none of the smoke values are keyframed. It is as if the heat difference of the outflow is changing. I have seen it start to happen at about frame 1000 in one scene and around frame 2000 in another scene.

I have noticed it happen quicker (frame 1000) when the domain's x size was twice the y and z size (rectangular shape). The sample blend has even x, y, & z size and starts rising around frame 2000.

I have posted a video showing the problem. The video is from the sample file. The smoke should not rise from the emitter. The video is about 2 minutes long and the smoke starts to rise from the emitter about half way through. The video is at http://vimeo.com/10156657.

At least one other forum member says he has had the same problem.

I am running on Windows 7 64-bit with ATI 3870. I have tried different SVN versions, the latest being build 27449.

Followup

Message

Date: 2010-04-05 18:52
Sender: David Tilman
Miikah had responded on Blenderartists.org with the reason this was happening and a patch (http://blenderartists.org/forum/showthread.php?t=181649&page=2). From the thread:

I did some testing with this bug and it seems to be related to domain border behavior.

Currently domain "walls" are handled as obstacles but top and bottom sides as "outflows". This causes a strange effect when using wind effector. Fluid sort of stacks in the walls and forms a vortex pointing new smoke to go up instead.

I'm going to write a patch that allows you to select whether the walls are handled as obstacles or not. That should fix this issue.

--------------------------------

Ok, I just finished my patch.

You can download it here: http://www.miikah.org/smoke_collision_patch.patch
For Windows builds, check my site: http://www.miikahweb.com/indexen.php?p_id=blenderbuilds

If it seems to work fine, it may be added into trunk sooner or later.

Date: 2010-05-04 13:57
Sender: Joseph Eagar
danial: would be nice if you could look at this soon :)

Date: 2010-05-04 14:28
Sender: Daniel Genrich
Well, this patch is missing one detail :-)
setNeumannY / setNeumannX / setNeumannZ must be changed:
In every of that functions there is the part of "// fix, force top slab to only allow outwards flux".
This code part should only be called in case of "no border for this axis". No idea if we should seperate top/bottom here, too.

Date: 2010-12-15 12:25
Sender: Ton Roosendaal
David / Daniel: this report is unanswered too long now, can you update on the status for it?

Date: 2010-12-15 13:17
Sender: Ton Roosendaal
Has been added to svn in the mean time. closed!

Attached Files:

Name	Date	Download

SmokeTest04.blend	2010-03-16 04:03	Download

Changes:

Field	Old Value	Date	By

status_id	Open	2010-12-15 13:17	ton
close_date	None	2010-12-15 13:17	ton
Status	New	2010-12-15 13:17	ton
Status	None	2010-12-10 11:59	jesterking
assigned_to	none	2010-04-05 14:04	blendix
File Added	10357: SmokeTest04.blend	2010-03-16 04:03	davidt