Property controlled drivers not updating from python #74000

New Issue

Shay Gusin · 2020-02-19T10:43:00+01:00

Shay Gusin commented

2020-02-19 10:43:00 +01:00

System Information
Operating system: MacOS / Unbuntu 18.04
Graphics card: Mac / Nvidia 2080TI

Broken: 2.82.7
Worked: 2.79.7

I have custom property that controls a driver.
there are couple of meshes that change visibility depending on the property value.
When manually changing the custom property value everything works perfectly.
The problem happens when accessing the custom property from python code, and changing the value,
the value on the property changes but the visibility of the meshes controlled by the drivers does not change.
Also on the outliner there's no change in the visibility indication of the meshes.

Expected behaviour:
When changing the property from python code, one mesh becomes invisible and another becomes visible.

**System Information** Operating system: MacOS / Unbuntu 18.04 Graphics card: Mac / Nvidia 2080TI Broken: 2.82.7 Worked: 2.79.7 I have custom property that controls a driver. there are couple of meshes that change visibility depending on the property value. When manually changing the custom property value everything works perfectly. The problem happens when accessing the custom property from python code, and changing the value, the value on the property changes but the visibility of the meshes controlled by the drivers does not change. Also on the outliner there's no change in the visibility indication of the meshes. Expected behaviour: When changing the property from python code, one mesh becomes invisible and another becomes visible.

Shay Gusin commented

2020-02-19 10:43:00 +01:00

Added subscriber: @shayg

Demeter Dzadik commented

2020-02-19 11:28:30 +01:00

Added subscriber: @Mets

Demeter Dzadik commented

2020-02-19 11:28:30 +01:00

Probably same underlying issue as studio/blender-studio#73593?

Richard Antalik commented

2020-02-19 17:32:33 +01:00

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

Sybren A. Stüvel commented

2020-02-20 11:21:15 +01:00

Added subscriber: @dr.sybren

Sybren A. Stüvel commented

2020-02-20 11:21:15 +01:00

Changed status from 'Confirmed' to: 'Needs User Info'

Sybren A. Stüvel commented

2020-02-20 11:21:15 +01:00

@shayg please provide a minimal blend file that demonstrates the issue.

Shay Gusin commented

2020-02-24 12:45:44 +01:00

Food_Apple.blend

Attached is the file for which there's a problem.
Also this is the code to run:

import bpy
import bmesh

context = bpy.context

apple = bpy.context.scene.objects['controler']

apple['change_model'] = 5
context.scene.frame_set(0)

[Food_Apple.blend](https://archive.blender.org/developer/F8366252/Food_Apple.blend) Attached is the file for which there's a problem. Also this is the code to run: ``` import bpy import bmesh context = bpy.context apple = bpy.context.scene.objects['controler'] apple['change_model'] = 5 context.scene.frame_set(0) ```

Sybren A. Stüvel commented

2020-02-25 12:47:55 +01:00

Changed status from 'Needs User Info' to: 'Archived'

Sybren A. Stüvel closed this issue

2020-02-25 12:47:55 +01:00

Sybren A. Stüvel self-assigned this 2020-02-25 12:47:55 +01:00

Sybren A. Stüvel commented

2020-02-25 12:47:55 +01:00

That blend file (Food_Apple.blend) is set up incorrectly; the custom property is set on the Scene, but the driver is accessing it on the Object. I have corrected this in #74000-visibility-driver.blend.
The code also doesn't work with that blend file:

>>> apple = bpy.context.scene.objects['controler']

Traceback (most recent call last):
  File "<blender_console>", line 1, in <module>
KeyError: 'bpy_prop_collection[key]: key "controler" not found'

But I get the gist of your report.

The thing is that assignments to custom properties don't tag the object for updates in the dependency graph. Since tagging for update on an object is expensive (it recalculates the constraints, modifiers, and thus the geometry) this is not done automatically from Python assignments. This code works in the attached blend file in the Python console:

# The file is saved with ['hidden'] = 0 and the Cube as the active object.
C.object['hidden'] = 1
C.object.update_tag()
C.scene.frame_set(C.scene.frame_current+1)

Marking as 'invalid' as this is not a bug in Blender.

That blend file (Food_Apple.blend) is set up incorrectly; the custom property is set on the Scene, but the driver is accessing it on the Object. I have corrected this in [#74000-visibility-driver.blend](https://archive.blender.org/developer/F8369224/T74000-visibility-driver.blend). The code also doesn't work with that blend file: ``` >>> apple = bpy.context.scene.objects['controler'] Traceback (most recent call last): File "<blender_console>", line 1, in <module> KeyError: 'bpy_prop_collection[key]: key "controler" not found' ``` But I get the gist of your report. The thing is that assignments to custom properties don't tag the object for updates in the dependency graph. Since tagging for update on an object is expensive (it recalculates the constraints, modifiers, and thus the geometry) this is not done automatically from Python assignments. This code works in the attached blend file in the Python console: ``` # The file is saved with ['hidden'] = 0 and the Cube as the active object. C.object['hidden'] = 1 C.object.update_tag() C.scene.frame_set(C.scene.frame_current+1) ``` Marking as 'invalid' as this is not a bug in Blender.

Shay Gusin commented

2020-02-25 13:32:59 +01:00

Hi @dr.sybren, thanks for the update.

Is there a reason to move to the next frame?
As I understand the setting the current frame will also trigger an update.
Also the actual file is more complex, drivers control more than one object so when performing what you suggest some objects that supposed to appear remain hidden and others.
So if I want to control the top of the apple when I switch the property, sometimes the apple appears without the top at all.

Hi @dr.sybren, thanks for the update. Is there a reason to move to the next frame? As I understand the setting the current frame will also trigger an update. Also the actual file is more complex, drivers control more than one object so when performing what you suggest some objects that supposed to appear remain hidden and others. So if I want to control the top of the apple when I switch the property, sometimes the apple appears without the top at all.

Sybren A. Stüvel commented

2020-02-25 13:42:14 +01:00

In #74000#879987, @shayg wrote:
Is there a reason to move to the next frame?
As I understand the setting the current frame will also trigger an update.

I didn't test with the current frame.

Also the actual file is more complex, drivers control more than one object so when performing what you suggest some objects that supposed to appear remain hidden and others.
So if I want to control the top of the apple when I switch the property, sometimes the apple appears without the top at all.

The object to tag for update is the object that contains the custom property. Drivers that depend on that property value should all be automatically updated.

> In #74000#879987, @shayg wrote: > Is there a reason to move to the next frame? > As I understand the setting the current frame will also trigger an update. I didn't test with the current frame. > Also the actual file is more complex, drivers control more than one object so when performing what you suggest some objects that supposed to appear remain hidden and others. > So if I want to control the top of the apple when I switch the property, sometimes the apple appears without the top at all. The object to tag for update is the object that contains the custom property. Drivers that depend on that property value should all be automatically updated.

Élie Michel commented

2020-07-23 15:15:55 +02:00

Added subscriber: @elie

Élie Michel commented

2020-07-23 15:15:55 +02:00

I am experiencing similar issue with object drivers targetting scene properties. Unfortunately calling scene.update_tag() does not trigger the update of object's driven attributes.

edit: my issue was that the 3D view was not redrawn, so I added:

for area in bpy.context.screen.areas:
    if area.type == 'VIEW_3D':
        area.tag_redraw()

I am experiencing similar issue with object drivers targetting scene properties. Unfortunately calling `scene.update_tag()` does not trigger the update of object's driven attributes. edit: my issue was that the 3D view was not redrawn, so I added: ``` for area in bpy.context.screen.areas: if area.type == 'VIEW_3D': area.tag_redraw() ```

Bay Raitt commented

2022-03-20 10:32:15 +01:00

Added subscriber: @spiraloid-3

Bay Raitt commented

2022-03-20 10:32:16 +01:00

here's a hacky catchall I used to force an update when all the other solutions failed me.

  for obj in bpy.context.scene.objects:
      obj.hide_render = obj.hide_render

here's a hacky catchall I used to force an update when all the other solutions failed me. ``` for obj in bpy.context.scene.objects: obj.hide_render = obj.hide_render

Harry McKenzie commented

2022-12-29 06:01:50 +01:00

Added subscriber: @Harry-Kunz

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Property controlled drivers not updating from python #74000