Difficulty reading updated scene information in a script #1250

sqward · 2019-12-06T16:59:20Z

I have an export script which I execute in Blender 2.81 in headless mode (on commandline). It's meant to export and animation I've created using Animation Nodes. My script worked fine in 2.79. In 2.81 my object animation is not updated: for every scene.frame_set() position, rotatino etc. is the same.

Can you help me get to the bottom of the problem? I must be missing something that was introduced in Blender 2.8?

Regards

OmarEmaraDev · 2019-12-06T17:01:24Z

This seems like the issue reported in #1171, is this the issue you are having?

sqward · 2019-12-06T17:06:16Z

I've tried to render my animation and it seems to behave as expected.

OmarEmaraDev · 2019-12-06T17:08:14Z

So the issue only occur when you are rendering from the command line?

sqward · 2019-12-06T17:09:30Z

I'm not even rendering. My aim is to export animation data. So for every frame I captura object transform and store it. But I don't render anything.

OmarEmaraDev · 2019-12-06T17:12:24Z

So you have a node tree that sets the transformation of the object, and then you run a script that access the transformation of the object?

sqward · 2019-12-06T17:17:13Z

That's correct.

…

On Fri, 6 Dec 2019, 18:12 Omar Emara, ***@***.***> wrote: So you have a node tree that sets the transformation of the object, and then you run a script that access the transformation of the object? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1250?email_source=notifications&email_token=AAEZGV2HLSJWAG7EMACKEYTQXKBXRA5CNFSM4JW4ZYN2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEGEX3ZQ#issuecomment-562658790>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEZGVYZBLFWXQMKNOYKCKLQXKBXRANCNFSM4JW4ZYNQ> .

OmarEmaraDev · 2019-12-06T17:25:49Z

Can you share a minimal file that reproduces the issue?

sqward · 2019-12-06T17:27:01Z

I will prepare one. Thanks for prompt response.

…

On Fri, 6 Dec 2019, 18:25 Omar Emara, ***@***.***> wrote: Can you share a minimal file that reproduces the issue? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1250?email_source=notifications&email_token=AAEZGV7UMS7MLQINOX5XH5TQXKDJ5A5CNFSM4JW4ZYN2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEGEZCQI#issuecomment-562663745>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEZGVZEZXY6I7BMLMTIPO3QXKDJ5ANCNFSM4JW4ZYNQ> .

sqward · 2019-12-10T22:49:46Z

Hi and sorry for delay.

My toy export script looks like this:

import bpy

def printObjectPosition(obj):
    print(obj.name, obj.matrix_world.to_translation())

def convertAnimation(scene):
    objs = scene.objects
    scene.frame_set(scene.frame_start)
    printObjectPosition(objs["Plane"])   
    printObjectPosition(objs["Plane.001"])   
    scene.frame_set(scene.frame_start+100)
    printObjectPosition(objs["Plane"])   
    printObjectPosition(objs["Plane.001"])   
  
convertAnimation(bpy.data.scenes['Scene'])

and blender invocation looks like this:

$ ../sv2017/src/Tools/blender-2.81a-windows64/blender.exe -noaudio -y --background an_test.blend -P export_example.py
Blender 2.81 (sub 16) (hash f1aa4d18d49d built 2019-12-04 14:30:40)
Read prefs: C:\Users\sqward\AppData\Roaming\Blender Foundation\Blender\2.81\config\userpref.blend
found bundled python: C:\Work\devel\sv2017\src\Tools\blender-2.81a-windows64\2.81\python
Read blend: C:\Work\devel\animation_nodes_export\an_test.blend
Registered Animation Nodes
Plane <Vector (-0.5003, 1.7544, 0.0000)>
Plane.001 <Vector (4.2274, 0.1166, 0.0000)>
Plane <Vector (-0.5003, 1.7544, 0.0000)>
Plane.001 <Vector (0.5983, -0.7396, 0.0000)>

My attached blend file contains two objects: "Plane" which is driven by AN and "Plane.001" which moved via key frames.

Note how position of "Plane.001" changes between scene.frame_set(scene.frame_start) and scene.frame_set(scene.frame_start+100) but not for "Plane".

This worked fine in 2.7x. Am I missing a trick in 2.8x?

an_test.zip

OmarEmaraDev · 2019-12-11T09:36:25Z

Animation Nodes needs to execute when you change the current frame in order for the object location to be updated. Animation Nodes can only see such change in the current frame after the script finish execution, so Auto Execution is not an option. To fix this, you just need to execute the node tree yourself when needed. Your script should be something like:

import bpy

def printObjectPosition(obj):
    print(obj.name, obj.matrix_world.to_translation())

def convertAnimation(scene):
    objs = scene.objects
    scene.frame_set(scene.frame_start)
    printObjectPosition(objs["Plane"])   
    printObjectPosition(objs["Plane.001"])   
    scene.frame_set(scene.frame_start+100)
    bpy.data.node_groups['NodeTree'].execute() # Execute node tree after changing frame.
    printObjectPosition(objs["Plane"])   
    printObjectPosition(objs["Plane.001"])   
  
convertAnimation(bpy.data.scenes['Scene'])

Makes sense?

sqward · 2019-12-11T09:38:45Z

Yes. That makes perfect sense. I'm only curious why this wasn't necessary in 2.79? Regards.

…

On Wed, 11 Dec 2019, 09:36 Omar Emara, ***@***.***> wrote: Animation Nodes needs to execute when you change the current frame in order for the object location to be updated. Animation Nodes can only see such change in the current frame after the script finish execution, so Auto Execution is not an option. To fix this, you just need to execute the node tree yourself when needed. Your script should be something like: import bpy def printObjectPosition(obj): print(obj.name, obj.matrix_world.to_translation()) def convertAnimation(scene): objs = scene.objects scene.frame_set(scene.frame_start) printObjectPosition(objs["Plane"]) printObjectPosition(objs["Plane.001"]) scene.frame_set(scene.frame_start+100) bpy.data.node_groups['NodeTree'].execute() # Execute node tree after change frame. printObjectPosition(objs["Plane"]) printObjectPosition(objs["Plane.001"]) convertAnimation(bpy.data.scenes['Scene']) Makes sense? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1250?email_source=notifications&email_token=AAEZGV5JJKADRL6K6BA77GTQYCYBVA5CNFSM4JW4ZYN2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEGSPF2Y#issuecomment-564458219>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEZGV6S7K4W225ALJTVNELQYCYBVANCNFSM4JW4ZYNQ> .

OmarEmaraDev · 2019-12-11T10:36:22Z

Blender 2.8 removed the ALWAYS event handler we used in 2.7x to implement Auto Execution, so now we use an infinite timer. I don't know exactly why this happens, but that must be the cause of this.

sqward · 2019-12-11T11:35:30Z

Thanks. But if my node uses "frame changed" handler then shouldn't that work? I never use ALWAYS for updates as this drains the CPU a lot.

…

On Wed, 11 Dec 2019 at 10:36, Omar Emara ***@***.***> wrote: Blender 2.8 removed the ALWAYS event handler we used in 2.7x to implement Auto Execution, so now we use an infinite timer. I don't know exactly why this happens, but that must be the cause of this. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1250?email_source=notifications&email_token=AAEZGV2ERT7GTXDJALDQKGTQYC7CPA5CNFSM4JW4ZYN2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEGSU3OQ#issuecomment-564481466>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEZGVZHHWEZ4P3CO6KGNHTQYC7CPANCNFSM4JW4ZYNQ> .

OmarEmaraDev · 2019-12-11T11:46:09Z

If you enable Auto Execution, Animation Nodes is always executing as many times as possible, even if the Always option is disabled. Animation Nodes does not use a proper trigger system for auto execution. For instance, when you enable Frame Changed, in the background, the frame value is retrieved and stored as a string, then it is compared to the previously stored value, if Animation Nodes notices that the value changed, it then executes the node tree.

To summarize, if you disable the Always option, Animation Nodes is still always executing an internal trigger mechanism.

sqward · 2019-12-11T11:49:58Z

Ok, thanks. I'll try your solution when I'll get back home. Regards.

…

On Wed, 11 Dec 2019 at 11:46, Omar Emara ***@***.***> wrote: If you enable Auto Execution, Animation Nodes is always executing as many times as possible, even if the *Always* option is disabled. Animation Nodes does not use a proper trigger system for auto execution. For instance, when you enable *Frame Changed*, in the background, the frame value is retrieved and stored as a string, then it is compared to the previously stored value, if Animation Nodes notices that the value changed, it then executes the node tree. To summarize, if you disable the *Always* option, Animation Nodes is still always executing an internal trigger mechanism. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1250?email_source=notifications&email_token=AAEZGV2Q6IOMWJ4BHFL3CCTQYDHIFA5CNFSM4JW4ZYN2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEGS2RSQ#issuecomment-564504778>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAEZGV2SR26NDXGWK2RNPEDQYDHIFANCNFSM4JW4ZYNQ> .

sqward · 2019-12-11T19:34:15Z

bpy.data.node_groups['NodeTree'].execute() doesn't seem to help. Position of "Plane" object is not updated. Did it work for you? Regards

OmarEmaraDev · 2019-12-11T21:52:06Z

Yes, it works with the blend file you sent.

sqward · 2019-12-11T21:56:20Z

Position of "Plane" stays the same after calling execute. Could that be platform difference?

$ ../sv2017/src/Tools/blender-2.81a-windows64/blender.exe -noaudio -y --background an_test.blend -P export_example.py
Blender 2.81 (sub 16) (hash f1aa4d18d49d built 2019-12-04 14:30:40)
Read prefs: C:\Users\sqward\AppData\Roaming\Blender Foundation\Blender\2.81\config\userpref.blend
found bundled python: C:\Work\devel\sv2017\src\Tools\blender-2.81a-windows64\2.81\python
Read blend: C:\Work\devel\animation_nodes_export\an_test.blend
Registered Animation Nodes
Plane <Vector (0.3774, 1.7612, 0.0000)>
Plane.001 <Vector (4.2274, 0.1166, 0.0000)>
Plane <Vector (0.3774, 1.7612, 0.0000)>
Plane.001 <Vector (0.5983, -0.7396, 0.0000)>

sqward · 2019-12-11T22:48:36Z

It doesn't work for me from within Blender either:

OmarEmaraDev · 2019-12-12T08:30:09Z

Please note that Blender doesn't update matrices by default when they are changed, so you have to update them yourself. You can use the Update Matrices node for that.

But preferably, you should update them before reading them in the script.

sqward · 2019-12-12T20:14:28Z

It seems to work for me now from within Blender, but not when executed from the commandline.
Any idea?

OmarEmaraDev · 2019-12-12T20:32:28Z

hmmmm, no. Can you update the matrices from the script itself. See:
https://stackoverflow.com/questions/13840418/force-matrix-world-to-be-recalculated-in-blender

Otherwise, I would consider this a bug as in #1171.

sqward · 2019-12-12T20:35:00Z

I see my object.location doesn't change so world_matrix would be the same.

OmarEmaraDev · 2019-12-13T08:42:35Z

In this case, I would need to investigate this further. Might take some time, sorry.

OmarEmaraDev · 2020-02-17T18:04:06Z

Fixed in #1294 and b1ac938.

sqward · 2020-02-17T20:28:40Z

Thanks! I tried to find a relevant build but had no luck. Is that available?

OmarEmaraDev · 2020-02-17T20:31:33Z

Should be available in https://animation-nodes.com/

sqward · 2020-02-17T20:36:58Z

Thanks. In that case the might be something wrong with the build:

OmarEmaraDev · 2020-02-17T20:47:55Z

See #1240.

sqward · 2020-02-17T22:01:39Z

Thanks. I can run it now.

Sadly, the above toy script still doesn't work. I've tried all your earlier suggestions (except bpy.data.node_groups['NodeTree'].execute() which doesn't seem to work at all).

OmarEmaraDev · 2020-02-18T08:14:02Z

hmm, let me test this again.

OmarEmaraDev · 2020-02-18T09:53:43Z

It seems to be working fine for me:

┌─[omar]──[~/Desktop]
└─╼ blender -noaudio -y --background an_test.blend -P export_example.py
Blender 2.83 (sub 4) (hash dcb905a58f59 built 2020-02-17 14:36:20)
Read prefs: /home/omar/.config/blender/2.83/config/userpref.blend
/run/user/1000/gvfs/ non-existent directory
Registered Animation Nodes
Read blend: /home/omar/Desktop/an_test.blend
Plane <Vector (0.3774, 1.7612, 0.0000)>
Plane.001 <Vector (4.2274, 0.1166, 0.0000)>
Plane <Vector (-2.3628, -1.3816, 0.0000)>
Plane.001 <Vector (0.5983, -0.7396, 0.0000)>

Blender quit

This was using your original toy script:

import bpy

def printObjectPosition(obj):
    print(obj.name, obj.matrix_world.to_translation())

def convertAnimation(scene):
    objs = scene.objects
    scene.frame_set(scene.frame_start)
    printObjectPosition(objs["Plane"])   
    printObjectPosition(objs["Plane.001"])   
    scene.frame_set(scene.frame_start+100)
    printObjectPosition(objs["Plane"])   
    printObjectPosition(objs["Plane.001"])   
  
convertAnimation(bpy.data.scenes['Scene'])

We now execute automatically on frame_set, so you don't have to execute manually.

Can you test with 2.83? Just so that we have the same setup and can debug this better.

sqward · 2020-02-18T19:59:00Z

Ok, it seem to work on 2.83... But I had to remove the "Update Object Matrices" node. Is this what you'd expect? Regards

OmarEmaraDev · 2020-02-18T20:01:48Z

Not exactly. Does it fail with the Update Object Matrices node there?

sqward · 2020-02-18T20:02:18Z

Yes, It fails to update the positions.

OmarEmaraDev · 2020-02-18T20:09:36Z

I am not entirely sure why this is the case. It could be that the depsgraph at this point is not up to date. But look at the bright side, it works. 😀

sqward · 2020-02-18T20:13:59Z

Indeed. Thanks! :)

sqward closed this as completed Dec 11, 2019

sqward reopened this Dec 11, 2019

OmarEmaraDev closed this as completed Feb 17, 2020

Difficulty reading updated scene information in a script #1250

Difficulty reading updated scene information in a script #1250

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