"Join Meshes" changes the material slot assigned to faces of the original mesh #85578

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opened 2021-02-12 10:10:37 +01:00 by Ilja Razinkov · 6 comments

Ilja Razinkov commented

2021-02-12 10:10:37 +01:00

System Information
Operating system: MacOs BigSur

Blender Version
Broken: 2.91.2

Short description of error
See video:
Screen Recording 2021-02-12 at 12.04.24.mov

Exact steps for others to reproduce the error

Create Mesh ONE with 2 material slots, with the same material, each slot assigned to different mesh island in mesh.
So faces on mesh islands have different material_indexes, although both use the same material (in different material slots)
Create Mesh TWO without any materials
Join Mesh TWO into Mesh ONE
Check material indexes in resulted mesh. They wil ALL point to first material slots.
Faces, that was linked to second material slot initially will be "relinked" to first slot, so theier material_index attributes are altered/messed

Expected behaviour:
Faces linked to second material slot initially should stay with the same material_index, join action has no reason to change them

**System Information** Operating system: MacOs BigSur **Blender Version** Broken: 2.91.2 **Short description of error** See video: [Screen Recording 2021-02-12 at 12.04.24.mov](https://archive.blender.org/developer/F9793793/Screen_Recording_2021-02-12_at_12.04.24.mov) **Exact steps for others to reproduce the error** 1) Create Mesh ONE with 2 material slots, with the same material, each slot assigned to different mesh island in mesh. So faces on mesh islands have different material_indexes, although both use the same material (in different material slots) 2) Create Mesh TWO without any materials 3) Join Mesh TWO into Mesh ONE 4) Check material indexes in resulted mesh. They wil ALL point to first material slots. Faces, that was linked to second material slot initially will be "relinked" to first slot, so theier material_index attributes are altered/messed **Expected behaviour:** Faces linked to second material slot initially should stay with the same material_index, join action has no reason to change them

Ilja Razinkov commented

2021-02-12 10:10:37 +01:00

Author

Added subscriber: @IPv6

Added subscriber: @IPv6

Germano Cavalcante changed title from ~~"Join Meshes" action messing up material indexes on resulted mesh~~ to "Join Meshes" changes the material slot assigned to faces of the original mesh

2021-02-16 16:00:09 +01:00

Germano Cavalcante commented

2021-02-16 16:00:09 +01:00

Member

Changed status from 'Needs Triage' to: 'Confirmed'

Changed status from 'Needs Triage' to: 'Confirmed'

Germano Cavalcante commented

2021-02-16 16:00:18 +01:00

Member

Added subscriber: @mano-wii

Added subscriber: @mano-wii

Philipp Oeser removed the

label 2023-02-09 15:28:42 +01:00

Germano Cavalcante referenced this issue

2023-10-16 17:35:19 +02:00

Volume-type geometries always seem to use the object material while mesh primitives are unpredictable #113712

Henrique Corrêa commented

2023-12-15 02:55:13 +01:00

I'm facing an issue that might be related to this (tested in 4.1 alpha). I'm working on a project that requires programmatically linking and unlinking materials from slots. When joining (Ctrl + J) a mesh with two materials into another with multiple unlinked slots, I noticed (unfortunately too late) that most of them got scrambled. Thankfully the issue doesn't seem to happen if all slots have materials assigned to them.

Is there any way this can get looked into? I don't know much about Blender's inner workings but this seems like a relatively simple bug to fix.

I'm facing an issue that might be related to this (tested in 4.1 alpha). I'm working on a project that requires programmatically linking and unlinking materials from slots. When joining (Ctrl + J) a mesh with two materials into another with multiple unlinked slots, I noticed (unfortunately too late) that most of them got scrambled. Thankfully the issue doesn't seem to happen if all slots have materials assigned to them. Is there any way this can get looked into? I don't know much about Blender's inner workings but this seems like a relatively simple bug to fix. <video src="/attachments/f16e599e-ed72-4b68-af3e-deaa76fab1c4" title="2023-12-14 22-36-54.mp4" controls></video>

4.5 KiB

2023-12-14 22-36-54.mp4

2.0 MiB

Iliya Katushenock commented

2023-12-15 09:08:22 +01:00

Member

This is not issue for geometry nodes, fix could be in replacing this operator by geometry nodes tool.

This is not issue for geometry nodes, fix could be in replacing this operator by geometry nodes tool.

Henrique Corrêa commented

2023-12-15 14:48:57 +01:00

GN is even worse. #106578 #91048 #99197

I had to give up on using it for my project because I ran into a lot of issues (which just like this one have been reported a long time ago and are still not fixed).

GN is even worse. #106578 #91048 #99197 I had to give up on using it for my project because I ran into a lot of issues (which just like this one have been reported a long time ago and are still not fixed).

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