Attempting to modify UVs with bpy results in crash with EXCEPTION_ACCESS_VIOLATION #112342

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Jonko · 2023-09-13T18:24:50+02:00

Jonko commented

2023-09-13 18:24:50 +02:00

System Information
Operating system: Windows 11
Graphics card: Intel Iris Xe Graphics

Blender Version
Broken: 3.5.1, 3.6.2, 4.0.0-alpha+main.fca8df9415b1-windows.amd64-release
Worked: 3.4.1

Short description of error
I wrote a basic plugin for Blender 3.4 to import a custom model format from a game I'm working on (specifically, I export the model data to a JSON file and then import that JSON using bpy). The script worked perfectly in 3.4, but when running in 3.6 (and tested on the latest 4.0 alpha as well), the script causes blender to crash. The specific error is:

Error   : EXCEPTION_ACCESS_VIOLATION
Address : 0x00007FF9BBBB832A
Module  : tbbmalloc.dll
Thread  : 00001afc
Writing: C:\Users\jonko\AppData\Local\Temp\blender.crash.txt
Error loading symbols C:\Program Files\Blender Foundation\Blender 3.6\blender.pdb
        error:0xc0000005
        size = 110227456
        base=0x00007FF613890000

blender.crash.txt is empty.

You can see my original script here. By commenting out stuff and trying to run it, I have narrowed down the cause to line 79:

uvlayer.data[loop_idx].uv = uvcoords[vert_idx]

I read that the MeshUVLoopLayer class was modified in Blender 3.5, so I tried upgrading this line to what looks like the new format:

uvlayer.uv[loop_idx].vector = uvcoords[vert_idx]

However, the same crash persists.

I have verified that both uvlayer.uv[loop_idx.vector and uvcoords[vert_idx] can be printed to the console without issue. I will also attach a sample model JSON file.

Exact steps for others to reproduce the error

Download the python script and model JSON file linked above
Comment out lines 14-21 and 81-84 of the script (these lines import the textures for mats -- they don't affect the crash in my testing and this simplifies things)
From the command line, run blender --background -noaudio -P ./sge_import.py ./OB0065O.sge.json blend (substituting the correct paths to those files)
Observe crash

Note: I'm running the script headless because it's faster, but the same crash occurs when you attempt to use it as an Import/Export add-on.

**System Information** Operating system: Windows 11 Graphics card: Intel Iris Xe Graphics **Blender Version** Broken: 3.5.1, 3.6.2, 4.0.0-alpha+main.fca8df9415b1-windows.amd64-release Worked: 3.4.1 **Short description of error** I wrote a basic plugin for Blender 3.4 to import a custom model format from a game I'm working on (specifically, I export the model data to a JSON file and then import that JSON using bpy). The script worked perfectly in 3.4, but when running in 3.6 (and tested on the latest 4.0 alpha as well), the script causes blender to crash. The specific error is: ``` Error : EXCEPTION_ACCESS_VIOLATION Address : 0x00007FF9BBBB832A Module : tbbmalloc.dll Thread : 00001afc Writing: C:\Users\jonko\AppData\Local\Temp\blender.crash.txt Error loading symbols C:\Program Files\Blender Foundation\Blender 3.6\blender.pdb error:0xc0000005 size = 110227456 base=0x00007FF613890000 ``` blender.crash.txt is empty. You can see my original script [here](https://github.com/haroohie-club/HeiretsuTranslationUtility/blob/main/HaruhiHeiretsuLib/Blender/sge_import.py). By commenting out stuff and trying to run it, I have narrowed down the cause to line 79: ```py uvlayer.data[loop_idx].uv = uvcoords[vert_idx] ``` I read that the MeshUVLoopLayer class was [modified in Blender 3.5](https://docs.blender.org/api/3.5/change_log.html#bpy-types-meshuvlooplayer), so I tried upgrading this line to what looks like the new format: ```py uvlayer.uv[loop_idx].vector = uvcoords[vert_idx] ``` However, the same crash persists. I have verified that both `uvlayer.uv[loop_idx.vector` and `uvcoords[vert_idx]` can be printed to the console without issue. I will also attach a sample model JSON file. **Exact steps for others to reproduce the error** 1. Download the python script and model JSON file linked above 2. Comment out lines 14-21 and 81-84 of the script (these lines import the textures for mats -- they don't affect the crash in my testing and this simplifies things) 3. From the command line, run `blender --background -noaudio -P ./sge_import.py ./OB0065O.sge.json blend` (substituting the correct paths to those files) 4. Observe crash Note: I'm running the script headless because it's faster, but the same crash occurs when you attempt to use it as an Import/Export add-on.

OB0065O.sge.json

916 KiB

Jonko added the

labels 2023-09-13 18:24:51 +02:00

Thomas Barlow commented

2023-09-13 18:59:21 +02:00

I think this might be duplicate of #107500 because the linked script creates the new uvlayer and the new color_layer and then tries to use the uvlayer variable that may no longer be valid because another layer (color_layer) was added afterwards.

    uvlayer = mesh.uv_layers.new()
    color_layer = mesh.vertex_colors.new()
    for face in mesh.polygons:
        for vert_idx, loop_idx in zip(face.vertices, face.loop_indices):
            color_layer.data[vert_idx].color = (colors[vert_idx]['R'], colors[vert_idx]['G'], colors[vert_idx]['B'], colors[vert_idx]['A'])
            uvlayer.data[loop_idx].uv = uvcoords[vert_idx]

For a potential workaround, I would suggest:

    uvlayer = mesh.uv_layers.new()
    uvlayer_name = uvlayer.name
    color_layer = mesh.vertex_colors.new()
    # Creating the color layer has invalidated the reference to the uv layer, so get it again.
    uvlayer = mesh.uv_layers[uvlayer_name]
    for face in mesh.polygons:
        for vert_idx, loop_idx in zip(face.vertices, face.loop_indices):
            color_layer.data[vert_idx].color = (colors[vert_idx]['R'], colors[vert_idx]['G'], colors[vert_idx]['B'], colors[vert_idx]['A'])
            uvlayer.data[loop_idx].uv = uvcoords[vert_idx]

Re-ordering the creation of the layers so that color_layer is created first would probably also work, but I wouldn't recommend it since its relying on the internal ordering of the layers.

I think this might be duplicate of https://projects.blender.org/blender/blender/issues/107500 because the linked script creates the new `uvlayer` and the new `color_layer` and then tries to use the `uvlayer` variable that may no longer be valid because another layer (`color_layer`) was added afterwards. ```py uvlayer = mesh.uv_layers.new() color_layer = mesh.vertex_colors.new() for face in mesh.polygons: for vert_idx, loop_idx in zip(face.vertices, face.loop_indices): color_layer.data[vert_idx].color = (colors[vert_idx]['R'], colors[vert_idx]['G'], colors[vert_idx]['B'], colors[vert_idx]['A']) uvlayer.data[loop_idx].uv = uvcoords[vert_idx] ``` For a potential workaround, I would suggest: ```py uvlayer = mesh.uv_layers.new() uvlayer_name = uvlayer.name color_layer = mesh.vertex_colors.new() # Creating the color layer has invalidated the reference to the uv layer, so get it again. uvlayer = mesh.uv_layers[uvlayer_name] for face in mesh.polygons: for vert_idx, loop_idx in zip(face.vertices, face.loop_indices): color_layer.data[vert_idx].color = (colors[vert_idx]['R'], colors[vert_idx]['G'], colors[vert_idx]['B'], colors[vert_idx]['A']) uvlayer.data[loop_idx].uv = uvcoords[vert_idx] ``` Re-ordering the creation of the layers so that `color_layer` is created first would probably also work, but I wouldn't recommend it since its relying on the internal ordering of the layers.

Jonko commented

2023-09-13 19:38:08 +02:00

It looks like it is a dupe of that bug because your solution fixed it! I'm going to close in favor of it. As long as this behavior is documented, I don't think it's a huge issue. Ideally, if you could add it to the 3.5 changenotes as well, that would have helped in discoverability.

Jonko closed this issue

2023-09-13 19:38:10 +02:00

Blender Bot added

and removed

labels 2023-09-13 19:38:12 +02:00

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