Grease Pencil materials can be assigned to non-Grease Pencil object types with Python #108672

New Issue

Ray Mairlot · 2023-06-06T18:02:10+02:00

Ray Mairlot commented

2023-06-06 18:02:10 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 516.59

Blender Version
Broken: version: 4.0.0 Alpha, branch: main, commit date: 2023-06-06 00:30, hash: bdd189f593ac
Worked: -

Short description of error
It is possible to assign a Grease Pencil material to a non-Grease Pencil object with Python. I don't know if this in itself is a bug, but several bugs happen after doing it, which makes me think you're not meant to be able to do this:

The following error appears in the console:

Traceback (most recent call last):
  File "C:\Blender Versions\Blender Launcher\daily\blender-4.0.0-alpha+daily.bdd189f593ac\4.0\scripts\startup\bl_ui\properties_grease_pencil_common.py", line 555, in draw
    if not is_grease_pencil_version3 and ob.data.use_stroke_edit_mode:
AttributeError: 'Mesh' object has no attribute 'use_stroke_edit_mode'

The material list on the object is drawn twice (see 'Double material list.png').

Exact steps for others to reproduce the error

Open the attached blend file.
Run the following script (which is included in the blend file):

import bpy

material = bpy.data.materials['Black']

bpy.data.objects['Cube'].material_slots[0].material = material

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 516.59 **Blender Version** Broken: version: 4.0.0 Alpha, branch: main, commit date: 2023-06-06 00:30, hash: `bdd189f593ac` Worked: - **Short description of error** It is possible to assign a Grease Pencil material to a non-Grease Pencil object with Python. I don't know if this in itself is a bug, but several bugs happen after doing it, which makes me think you're not meant to be able to do this: 1. The following error appears in the console: ``` Traceback (most recent call last): File "C:\Blender Versions\Blender Launcher\daily\blender-4.0.0-alpha+daily.bdd189f593ac\4.0\scripts\startup\bl_ui\properties_grease_pencil_common.py", line 555, in draw if not is_grease_pencil_version3 and ob.data.use_stroke_edit_mode: AttributeError: 'Mesh' object has no attribute 'use_stroke_edit_mode' ``` 2. The material list on the object is drawn twice (see 'Double material list.png'). **Exact steps for others to reproduce the error** 1. Open the attached blend file. 2. Run the following script (which is included in the blend file): ``` import bpy material = bpy.data.materials['Black'] bpy.data.objects['Cube'].material_slots[0].material = material ```

Assign Grease Material to Object bug.blend

1.3 MiB

Double material list.png

25 KiB

Ray Mairlot added the

labels 2023-06-06 18:02:10 +02:00

Richard Antalik commented

2023-06-06 21:08:29 +02:00

This is also possible by remapping users. In general it is possible to cause undesirable behavior with python, which may not be considered as a bug. There is no rule for this really so will confirm and let module decide.

Richard Antalik added

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Grease Pencil materials can be assigned to non-Grease Pencil object types with Python #108672