Driver script which executes bpy.context.scene.update() crashes Blender #43385

New Issue

No One · 2015-01-22T21:27:12+01:00

No One commented

2015-01-22 21:27:12 +01:00

Blender 2.73, b4d8fb5
Win7 x64

Driver script immediately crashes blender

When opening the attached file DriverCrash.blend, running the python script in the Text Editor via Ctrl-P, then pressing "Update Dependencies" in the Graph Editor, Blender will crash immediately.

When commenting out "bpy.context.scene.update()" Blender will not crash.

Here's the code for the driver:

import bpy
from math import *

def xzAngle(x,y,z):
    bpy.data.objects["Text"].location[1] = y
    bpy.data.curves["Text"].body = "%.2f" % degrees(atan2(z,x))
    bpy.context.scene.update()  # comment this out and it will not crash
    return atan2(z,x)
 
bpy.app.driver_namespace['xzAngle'] = xzAngle{F138847}

My intention was that the text is automatically updated (showing the angle of the vector in realtime)

Blender 2.73, b4d8fb5 Win7 x64 Driver script immediately crashes blender When opening the attached file [DriverCrash.blend](https://archive.blender.org/developer/F138848/DriverCrash.blend), running the python script in the Text Editor via Ctrl-P, then pressing "Update Dependencies" in the Graph Editor, Blender will crash immediately. When commenting out "bpy.context.scene.update()" Blender will not crash. Here's the code for the driver: import bpy from math import * ``` def xzAngle(x,y,z): bpy.data.objects["Text"].location[1] = y bpy.data.curves["Text"].body = "%.2f" % degrees(atan2(z,x)) bpy.context.scene.update() # comment this out and it will not crash return atan2(z,x) bpy.app.driver_namespace['xzAngle'] = xzAngle{F138847} ``` My intention was that the text is automatically updated (showing the angle of the vector in realtime)

No One commented

2015-01-22 21:27:12 +01:00

Changed status to: 'Open'

No One commented

2015-01-22 21:27:12 +01:00

Added subscriber: @noone

Bastien Montagne commented

2015-01-22 21:43:26 +01:00

Changed status from 'Open' to: 'Archived'

Bastien Montagne closed this issue

2015-01-22 21:43:26 +01:00

Bastien Montagne self-assigned this 2015-01-22 21:43:26 +01:00

Bastien Montagne commented

2015-01-22 21:43:26 +01:00

Thanks for the report, but no bug here, this is not, has never been and will never be intended to work. Modifying anything from within a driver expression is already a very bad idea, but calling scene.update() in that context is pure suicide!

As a rule of thumb, drivers shall only read data, never write anything.

Thanks for the report, but no bug here, this is not, has never been and will never be intended to work. Modifying anything from within a driver expression is already a very bad idea, but calling scene.update() in that context is pure suicide! As a rule of thumb, drivers shall only **read** data, never **write** anything.

Bastien Montagne commented

2015-01-22 21:46:17 +01:00

PS: to update a text, you could rather add a callback to e.g. scene_update handlers (http://www.blender.org/api/blender_python_api_2_73_2/bpy.app.handlers.html).

No One commented

2015-01-22 21:55:36 +01:00

Probably I should not assign the y location like this: bpy.data.objects["Text"].location- [x] = y and have the driver manipulate the same coordinate.

Still, Blender should not crash.

Probably I should not assign the y location like this: bpy.data.objects["Text"].location- [x] = y and have the driver manipulate the same coordinate. Still, Blender should not crash.

No One commented

2015-01-22 21:58:29 +01:00

Sorry, I had not seen,that you already answered. Thanks for the information. I agree that I should not write a driver like this, but Blender shouldn't crash either... :)

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Driver script which executes bpy.context.scene.update() crashes Blender #43385