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Linking Materials causes Regular Materials to be used in Grease Pencil
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Windows 64 bit
Graphics card: Nvidia GTX 750 Ti

Blender Version
Broken: 2.91 release, 2.92.0 alpha 9b17e71c23a9
Worked: ?

Short description of error
Using the Make Links > Materials operation, a regular material can be set on a Grease Pencil object.
This can cause crashes, for example on drawing with such a materials selected.

Instead, linking a regular material to a Grease Pencil object should not be possible.

Exact steps for others to reproduce the error

  1. Press Ctrl + L, select Materials
  2. Select the Grease Pencil object. The first material slot will display an empty line. Selecting it shows the Principled Shader.

Event Timeline

Falk David (filedescriptor) changed the task status from Needs Triage to Confirmed.Jan 6 2021, 11:11 AM
Falk David (filedescriptor) changed the subtype of this task from "Report" to "Bug".

I can reproduce this. The material does get linked. Drawing with that material or changing the settings in the material seems to override it with a GP material. On the cube, this causes a python error

location: <unknown location>:-1
Python: Traceback (most recent call last):
  File "/.../blender-git/build_linux/bin/2.92/scripts/startup/bl_ui/properties_grease_pencil_common.py", line 602, in draw
    if ob.data.use_stroke_edit_mode:
AttributeError: 'Mesh' object has no attribute 'use_stroke_edit_mode'

I would consider this to be a bug.