Simulation cache can not be saved for linked objects #36382

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Gatis Kurzemnieks · 2013-08-05T09:56:24+02:00

Gatis Kurzemnieks commented

2013-08-05 09:56:24 +02:00

%%%--- Operating System, Graphics card ---
Windows 8, 64 bit, GeForce 780gtx

- Blender version with error, and version that worked ---

All versions

- Short description of error ---

Simulation cache can not be saved for linked objects. I have character with soft body and cloth modifiers applied. When I link this character in other scene to animate - there is no way to save baked dynamics cache.

- Steps for others to reproduce the error (preferably based on attached .blend file) ---

make object with dynamics
link object in another scene
bake dynamics
try to save dynamics / reload scene - all is gone :(

%%%

%%%--- Operating System, Graphics card --- Windows 8, 64 bit, GeForce 780gtx - Blender version with error, and version that worked --- All versions - Short description of error --- Simulation cache can not be saved for linked objects. I have character with soft body and cloth modifiers applied. When I link this character in other scene to animate - there is no way to save baked dynamics cache. - Steps for others to reproduce the error (preferably based on attached .blend file) --- 1. make object with dynamics 2. link object in another scene 3. bake dynamics 4. try to save dynamics / reload scene - all is gone :( %%%

Gatis Kurzemnieks commented

2013-08-05 09:56:24 +02:00

Changed status to: 'Open'

Lukas Tönne commented

2013-08-05 14:30:42 +02:00

%%%This is a design limitation more than an actual bug: the baked cache data is part of the object data, which is always loaded from the original file when linked. The linked copy of such objects is usually made non-editable by disabling most operators and buttons, but internally it's just a copy of the data and can still be modified. The point cache baking also still "works" locally, but as you noticed the data gets discarded after reload.

Baking point cache data should happen in the original file where the actual object lives. Then the cache data will be loaded as part of the linked object. This solution, however, may not be ideal, since it's likely that the original file does not contain all the colliders and other objects that determine the simulation outcome.

Ideally one would separately store the actual linked object data and then create a local object in the scene that uses this linked data, while storing point cache locally. However, this would currently only work for particles with their separate ParticleSettings data block. Softbody and cloth otoh are just modifiers which store all the settings as part of the object itself, so it's impossible to disconnect from the object and link only the settings. I'm afraid this will have to wait until a physics/modifier redesign takes place ...%%%

%%%This is a design limitation more than an actual bug: the baked cache data is part of the object data, which is always loaded from the original file when linked. The linked copy of such objects is usually made non-editable by disabling most operators and buttons, but internally it's just a copy of the data and can still be modified. The point cache baking also still "works" locally, but as you noticed the data gets discarded after reload. Baking point cache data should happen in the original file where the actual object lives. Then the cache data will be loaded as part of the linked object. This solution, however, may not be ideal, since it's likely that the original file does not contain all the colliders and other objects that determine the simulation outcome. Ideally one would separately store the actual linked object data and then create a local object in the scene that uses this linked data, while storing point cache locally. However, this would currently only work for particles with their separate ParticleSettings data block. Softbody and cloth otoh are just modifiers which store all the settings as part of the object itself, so it's impossible to disconnect from the object and link only the settings. I'm afraid this will have to wait until a physics/modifier redesign takes place ...%%%

Brecht Van Lommel commented

2013-08-06 08:08:09 +02:00

%%%This is indeed a known limitation of the current physics and point cache system, so this report should be closed as a todo item.

There is a workaround to make local point caches for files with some python scripting, that was used for the Sintel open movie project. In each scene that you use the object, you can create a python script that runs on load and enables the disk cache setting on the point cache, and sets a unique file path to save it to. I don't have the Sintel DVD here but it had some scripts, maybe you can ask on blenderartists for that or see if there are other scripts online somewhere.%%%

%%%This is indeed a known limitation of the current physics and point cache system, so this report should be closed as a todo item. There is a workaround to make local point caches for files with some python scripting, that was used for the Sintel open movie project. In each scene that you use the object, you can create a python script that runs on load and enables the disk cache setting on the point cache, and sets a unique file path to save it to. I don't have the Sintel DVD here but it had some scripts, maybe you can ask on blenderartists for that or see if there are other scripts online somewhere.%%%

Brecht Van Lommel commented

2013-08-15 23:07:01 +02:00

%%%So it seems I was too quick, this apparently used to work until recently with the right configuration and is broken now (sometime since siggraph or around then according to Bassam). For objects in a group you could use pinning to show them in the properties editor, and then ensure you have library cache path enabled.

Duplicate report here:
https://projects.blender.org/tracker/?func=detail&atid=498&aid=36418&group_id=9%%%

%%%So it seems I was too quick, this apparently used to work until recently with the right configuration and is broken now (sometime since siggraph or around then according to Bassam). For objects in a group you could use pinning to show them in the properties editor, and then ensure you have library cache path enabled. Duplicate report here: https://projects.blender.org/tracker/?func=detail&atid=498&aid=36418&group_id=9%%%

Brecht Van Lommel commented

2013-08-23 19:39:01 +02:00

%%%So, I tried the steps in the other bug report and that particular case does not seem to be something that recently broke, maybe it's some other point cache configuration that used to work but now doesn't anymore.

What seems to work ok for me is enable Disk Cache and disable Use Library Path in the original .blend. Then you can bake per scene .blend, that's actually not too complex, no scripting required.%%%

%%%So, I tried the steps in the other bug report and that particular case does not seem to be something that recently broke, maybe it's some other point cache configuration that used to work but now doesn't anymore. What seems to work ok for me is enable Disk Cache and disable Use Library Path in the original .blend. Then you can bake per scene .blend, that's actually not too complex, no scripting required.%%%

Brecht Van Lommel commented

2013-09-03 18:31:17 +02:00

%%%I've added a message now to the point cache panel for linked objects, modified the Use Lib Path tooltip to be more clear, and grayed out the bake buttons in case disk cache is disabled. As far as I can tell this is working as it should now.%%%

Brecht Van Lommel commented

2013-09-03 18:31:17 +02:00

Changed status from 'Open' to: 'Resolved'

Brecht Van Lommel closed this issue

2013-09-03 18:31:17 +02:00

Mikhail Schalk commented

2013-09-22 23:15:16 +02:00

%%%The bake buttons are now grayed out even when disc cache is enabled. It just shows the info message.

Also, is there any way to at least enable the frame range settings too for the local bakes? It's sort of pointless being able to bake but not having control of the frame range.

Was a single script used in Sintel for this (if so, which one was it.) or was it a new/modified one for each shot file? If I can get it working I'll try and document it in a blog or video tutorial. Thanks.%%%

%%%The bake buttons are now grayed out even when disc cache is enabled. It just shows the info message. Also, is there any way to at least enable the frame range settings too for the local bakes? It's sort of pointless being able to bake but not having control of the frame range. Was a single script used in Sintel for this (if so, which one was it.) or was it a new/modified one for each shot file? If I can get it working I'll try and document it in a blog or video tutorial. Thanks.%%%

Brecht Van Lommel commented

2013-09-23 14:19:03 +02:00

%%%Fixed the buttons being grayed out when they shouldn't be.

Making the frame range local is not possible in the current design of Blender datablock linking. I don't have the files with me here, but what I think we basically had script that runs on load and overrides variables, frame ranges but also stiffness and such in case it needs to be tweaked for a particular shot.

ob = bpy.data.objects["SomeObject"]
cache = ob.modifiers["Cloth"].point_cache
cache.frame_start = ...
cache.frame_end = ...%%%

%%%Fixed the buttons being grayed out when they shouldn't be. Making the frame range local is not possible in the current design of Blender datablock linking. I don't have the files with me here, but what I think we basically had script that runs on load and overrides variables, frame ranges but also stiffness and such in case it needs to be tweaked for a particular shot. ob = bpy.data.objects["SomeObject"] cache = ob.modifiers["Cloth"].point_cache cache.frame_start = ... cache.frame_end = ...%%%

Mikhail Schalk commented

2013-09-24 16:22:38 +02:00

%%%I found it. finals_config.py in the Sintel production directory pro->Scripts->Modules folder.

It looks like Campbell hardcoded 67 cloth presets for Sintel alone in this single file. That's not very user-friendly. So that's not really a workable solution outside of a few people who know Blender internally pretty well (I read Bassam was using it on Tube, or at least was.)

I'm not at all familiar with python so I don't actually know what to do with that code you offered (sorry). It looks like just expressions that need to go into an actual script(?) Without being able to edit the settings also it's probably not going to be very useful so I'll probably just append the cloth objects this time, since my focus right now has to be on production. However if I can reverse engineer some of this code I'd like to try to write something that would be more generic and user-friendly. I assume it could be setup to, instead of having to hard-code each of the settings changes, create an actual UI panel (or use the existing cloth settings panel if that's possible?) to input the values. And of course make it non-object specific so the script can work for anything. Maybe develop it into an add-on in the medium term if there's interest.

It's not really a showstopper, but this would be nice to have for future productions as an add-on, at least until library linking gets rewritten in Blender.

Okay, thanks for indulging me. I started a BA thread, so I'll move this conversation there and off the bug tracker, for anyone interested in continuing the discussion: http://blenderartists.org/forum/showthread.php?309736-Library-Linking-Cloth-Simulation-Settings%%%

%%%I found it. finals_config.py in the Sintel production directory pro->Scripts->Modules folder. It looks like Campbell hardcoded 67 cloth presets for Sintel alone in this single file. That's not very user-friendly. So that's not really a workable solution outside of a few people who know Blender internally pretty well (I read Bassam was using it on Tube, or at least was.) I'm not at all familiar with python so I don't actually know what to do with that code you offered (sorry). It looks like just expressions that need to go into an actual script(?) Without being able to edit the settings also it's probably not going to be very useful so I'll probably just append the cloth objects this time, since my focus right now has to be on production. However if I can reverse engineer some of this code I'd like to try to write something that would be more generic and user-friendly. I assume it could be setup to, instead of having to hard-code each of the settings changes, create an actual UI panel (or use the existing cloth settings panel if that's possible?) to input the values. And of course make it non-object specific so the script can work for anything. Maybe develop it into an add-on in the medium term if there's interest. It's not really a showstopper, but this would be nice to have for future productions as an add-on, at least until library linking gets rewritten in Blender. Okay, thanks for indulging me. I started a BA thread, so I'll move this conversation there and off the bug tracker, for anyone interested in continuing the discussion: http://blenderartists.org/forum/showthread.php?309736-Library-Linking-Cloth-Simulation-Settings%%%

Gatis Kurzemnieks commented

2014-03-15 12:00:46 +01:00

In 2.7rc2 cache is still not saved. You can bake cache in scene with linked object and everything seems fine, but when you reload - all cache is lost. I tried all options - "use lib path" is not checked and "disk cache" is checked, but still no luck. Am I missing something?

Adam Priest commented

2014-03-28 21:22:36 +01:00

Added subscriber: @AdamTentacles

Adam Priest commented

2014-03-28 21:22:36 +01:00

I think I agree that this is an unfixed bug.

TEST CASE

Here is a .zip file:
http://tentacles.org.uk/temp/BakeLinkedDynamicsTest.zip

It contains two .blends.

One, "HairyBaseObject.blend", contains a single plane with a hair particle system with hair dynamics turned on. The hair system is tuned to have a disk-cache, without library paths. The single plane is in a group for export.

Two, "SceneWithLinks.blend", contains a linked group instance linking to HairyBaseObject.

Steps To Reproduce:

Load "SceneWithLinks.blend"
Un-Pin HairyBaseObject.
Re-Pin it.
Select "L HairyBaseObject" from objeect drop-menu
Click the cache's "Bake" button to bake the dynamics. Takes a few seconds.
Scrob the timeline slider back and forth, observe the hair falling under gravity.
Close blender
Re-open blender, loading "SceneWithLinks.blend"
Scrob the timeline slider backwards, observing the hair moving
Scrob the timeline slider forwards, observing the hair restoring to upright position due to the baked cache being deleted.

It seems Blender is invalidating the cache for all frame ahead of whatever frame you look at.

As a work-around I tried, after step 6, chmodding all the cache files to root, so blender couldn't delete them.

This seems to work in the simple test case here, though it's not helping on my crazy complicated work-in-progress scene unfortunately.

That's using 2.7 release version.

Hope the test case helps narrow it down, tried to write the kinda bug-report-update that I wish my testers would write.

I think I agree that this is an unfixed bug. TEST CASE ----------------------- Here is a .zip file: http://tentacles.org.uk/temp/BakeLinkedDynamicsTest.zip It contains two .blends. One, "HairyBaseObject.blend", contains a single plane with a hair particle system with hair dynamics turned on. The hair system is tuned to have a disk-cache, without library paths. The single plane is in a group for export. Two, "SceneWithLinks.blend", contains a linked group instance linking to HairyBaseObject. Steps To Reproduce: 1) Load "SceneWithLinks.blend" 2) Un-Pin HairyBaseObject. 3) Re-Pin it. 4) Select "L HairyBaseObject" from objeect drop-menu 5) Click the cache's "Bake" button to bake the dynamics. Takes a few seconds. 6) Scrob the timeline slider back and forth, observe the hair falling under gravity. 7) Close blender 8) Re-open blender, loading "SceneWithLinks.blend" 9) Scrob the timeline slider backwards, observing the hair moving 10) Scrob the timeline slider forwards, observing the hair restoring to upright position due to the baked cache being deleted. It seems Blender is invalidating the cache for all frame ahead of whatever frame you look at. As a work-around I tried, after step 6, chmodding all the cache files to root, so blender couldn't delete them. This seems to work in the simple test case here, though it's not helping on my crazy complicated work-in-progress scene unfortunately. That's using 2.7 release version. Hope the test case helps narrow it down, tried to write the kinda bug-report-update that I wish my testers would write.

Adam Priest commented

2014-03-31 21:41:05 +02:00

Ahha, okay. I can in fact make it work as I think it ought. Subtle little thing.

Presumably the linked object has some sort of "this object has a baked cache" flag.

When you link to that object, that flag is copied from the source object into the scene.

So if the scene containing the original object isn't baked, then when you link that object into another scene it treats the baked physics as a cache instead of a bake. Becasue the flag in the original object says it's not baked.

So to make things work properly, in this example test above, you need to open HairyBaseObject.blend and bake it, even if only one frame, then save the HairyBaseObject.blend file with a baked physics.

Then, when the SceneWithLinks is loaded it links to a BaseObject with a 'is baked' flag, and so doesn't delete the physics frames.

So. Bug is right to be closed, though the featuers/area certainly needs work. Hopefully that's the kinda thing that'll be worked on during Gooseberry I guess, linking and whatnot.

Hope that helps someone.

Ahha, okay. I can in fact make it work as I think it ought. Subtle little thing. Presumably the linked object has some sort of "this object has a baked cache" flag. When you link to that object, that flag is copied from the source object into the scene. So if the scene containing the original object isn't baked, then when you link that object into another scene it treats the baked physics as a cache instead of a bake. Becasue the flag in the original object says it's not baked. So to make things work properly, in this example test above, you need to open HairyBaseObject.blend and bake it, even if only one frame, then save the HairyBaseObject.blend file with a baked physics. Then, when the SceneWithLinks is loaded it links to a BaseObject with a 'is baked' flag, and so doesn't delete the physics frames. So. Bug is right to be closed, though the featuers/area certainly needs work. Hopefully that's the kinda thing that'll be worked on during Gooseberry I guess, linking and whatnot. Hope that helps someone.

Stephen Hamacek commented

2014-09-02 09:24:49 +02:00

Added subscriber: @StephenHamacek

Stephen Hamacek commented

2014-09-02 09:24:49 +02:00

@AdamTentacles thanks for posting, Glad there is a workaround—been trying to figure this out too.

Stephen Hamacek commented

2014-10-06 17:56:22 +02:00

Just a followup to confirm your experience @pre.

After baking a frame or two in the library file (I'm using lib path unchecked to keep bake in scene directory), I can then load my scene, hit 'free bake' to allow baking, then 'bake all dynamics' and the dummy frames stay put and the new bake goes in my scene directory without deleting on save.

@brecht This is still a bit messy I guess, but maybe we could have a kind of 'fake bake' checkbox to achieve this trick somehow. Might solve a lot of hassle till the system gets a rejig.

Cheers.

Just a followup to confirm your experience @pre. After baking a frame or two in the library file (I'm using lib path unchecked to keep bake in scene directory), I can then load my scene, hit 'free bake' to allow baking, then 'bake all dynamics' and the dummy frames stay put and the new bake goes in my scene directory without deleting on save. @brecht This is still a bit messy I guess, but maybe we could have a kind of 'fake bake' checkbox to achieve this trick somehow. Might solve a lot of hassle till the system gets a rejig. Cheers.

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Simulation cache can not be saved for linked objects #36382

TEST CASE