EXCEPTION_ACCESS_VIOLATION crash using python API - accessing vertex colors / assigning uv #112432

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Andrej · 2023-09-16T08:22:00+02:00

Andrej commented

2023-09-16 08:22:00 +02:00

Blender 3.6.2, Windows 11
I've met some crash running code from Python API and managed to narrow it down to the snippet below.

Way to reproduce:

Open blender default scene, select cube
Run the snippet below from text editor. Might need to run it multiple times (sometimes I get it from the first run, sometimes it crashes after 5-10 times)
Try to comment one of the lines vertex_colors = or uv_layer[i].uv = and crash will disappear.

import bpy
from mathutils import Vector

def updateMesh(context):
    mesh = context.object.data
    uv_layer = mesh.uv_layers.active.data
    
    # try to comment this line
    vertex_colors = mesh.vertex_colors.new().data
    
    for i in range(len(mesh.loops)):
        pass
        # or try to comment this line
        uv_layer[i].uv = Vector((1,1)).xy

updateMesh(bpy.context)

Blender 3.6.2, Windows 11 I've met some crash running code from Python API and managed to narrow it down to the snippet below. Way to reproduce: 1) Open blender default scene, select cube 2) Run the snippet below from text editor. Might need to run it multiple times (sometimes I get it from the first run, sometimes it crashes after 5-10 times) 3) Try to comment one of the lines `vertex_colors = ` or `uv_layer[i].uv = ` and crash will disappear. ```python import bpy from mathutils import Vector def updateMesh(context): mesh = context.object.data uv_layer = mesh.uv_layers.active.data # try to comment this line vertex_colors = mesh.vertex_colors.new().data for i in range(len(mesh.loops)): pass # or try to comment this line uv_layer[i].uv = Vector((1,1)).xy updateMesh(bpy.context) ```

Andrej added the

labels 2023-09-16 08:22:01 +02:00

Andrej changed title from ~~EXCEPTION_ACCESS_VIOLATION crash using python API - accessing vertex colors / assigning ui~~ to EXCEPTION_ACCESS_VIOLATION crash using python API - accessing vertex colors / assigning uv

2023-09-16 08:22:10 +02:00

Jesse Yurkovich commented

2023-09-16 08:40:02 +02:00

This is actually the same as #107500. Adding new vertex_colors will cause existing references to uv_layers (or similar) to become invalidated. Feel free to subscribe to the other task for updates. However, in general, it sounds like the best course of action is to reference the particular data layers each time it needs to be used and not cache them.

Jesse Yurkovich closed this issue

2023-09-16 08:40:04 +02:00

Blender Bot added

and removed

labels 2023-09-16 08:40:06 +02:00

Jesse Yurkovich added

and removed

labels 2023-09-16 08:40:14 +02:00

Andrej commented

2023-09-16 10:23:44 +02:00

Can confirm that creating vertex color first and only then accessing uv layer helped.

import bpy
from mathutils import Vector

def updateMesh(context):
    mesh = context.object.data
    
    vertex_colors = mesh.vertex_colors.new().data
    uv_layer = mesh.uv_layers.active.data
    
    for i in range(len(mesh.loops)):
        uv_layer[i].uv = Vector((1,1)).xy

updateMesh(bpy.context)

Can confirm that creating vertex color first and only then accessing uv layer helped. ```python import bpy from mathutils import Vector def updateMesh(context): mesh = context.object.data vertex_colors = mesh.vertex_colors.new().data uv_layer = mesh.uv_layers.active.data for i in range(len(mesh.loops)): uv_layer[i].uv = Vector((1,1)).xy updateMesh(bpy.context) ```

Andrej referenced this issue

2023-09-16 10:37:53 +02:00

Python API: Mesh editing: Editing uvs after normals with a previously assigned variable doesn't work #107500

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EXCEPTION_ACCESS_VIOLATION crash using python API - accessing vertex colors / assigning uv #112432