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Maniphest T100472

Copy Modifiers sets Data Transfer mapping incorrectly
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Description

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3060 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.15

Blender Version
Broken: version: 3.4.0 Alpha, branch: master, commit date: 2022-07-31 21:46, hash: rBca172677b1a7
Worked: Probably never?

Short description of error
Link / Transfer Data (Ctrl L) -> Copy Modifiers seems to be using layers indices (instead of names) to set Data Transfer layer mapping (specifically layers_vcol_loop_select_dst).
As the result, if target (selected) objects use different layer indices, the mapping in created modifiers won't match.

Exact steps for others to reproduce the error

copy_modifier_layers_mapping_bug.blend734 KBDownload

  1. Open the attached .blend, there are 2 cubes, both having layers with the same name, just with flipped indices.
  2. Copy the modifier by extending the selection to Cube1 (make active), Ctrl L -> Copy Modifiers.
  3. Check the Data Transfer created on Cube2 and it's colors layers mapping - you can see the destination layer is different from the one in Cube1 Data Transfer

Related Objects

Event Timeline

Jan Kadeřábek (jendabek) created this task.Aug 17 2022, 11:49 PM
Jan Kadeřábek (jendabek) updated the task description. (Show Details)Aug 17 2022, 11:52 PM
Jan Kadeřábek (jendabek) updated the task description. (Show Details)
Jan Kadeřábek (jendabek) updated the task description. (Show Details)
Pratik Borhade (PratikPB2123) closed this task as Archived.Aug 18 2022, 6:23 AM
Pratik Borhade (PratikPB2123) added a subscriber: Pratik Borhade (PratikPB2123).
In T84152#1086544, @mont29 wrote:

DataTransfer stores its operating layers as indices, there is nothing to be done here, and not a bug in any case

Hi, thanks for the report. As said in the above comment and in your report description, modifier uses indices and not the name
This is not a bug so closing your report. Feel free to comment if there is misunderstanding. I'll reopen the report in that case

Jan Kadeřábek (jendabek) added a comment.EditedAug 18 2022, 12:44 PM

Hi,
from the user standpoint I still consider this as a bug, as the result is not what user expects (it took some hours to even advanced user like me, to find out why my script which uses Link -> Copy Modifiers doesn't set mapping correctly).
Users work with layer names, not indices - I believe most users even don't know something like layer index exists, and even if they do, they can't manage them anyway.

If some action (like Copy Modifiers) gives unexpected results only because different layers order (which isn't even manageable), it should be considered as a bug in my opinion, despite it makes sense technically.
Even in Python you set dst and src layers by name.

Pratik Borhade (PratikPB2123) reopened this task as Needs Triage.Aug 18 2022, 12:49 PM
Richard Antalik (ISS) closed this task as Archived.Aug 18 2022, 1:44 PM
Richard Antalik (ISS) added a subscriber: Richard Antalik (ISS).

Unfortunately due to number of existing bugs we use strict definition of what bug is. I appreciate the report and would agree, that it could work better, But this is a request for improved behavior and not a bug in current behavior. This bug tracker is only for bugs and errors.

For user requests and feedback, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests
For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

Jan Kadeřábek (jendabek) added a comment.Aug 18 2022, 2:34 PM

We have a narrow view of what is considered a bug, typically this is limited to something that doesn't work as intended.
Is it intended that Copy Modifiers creates modifiers with different settings?
But I understand there are more important issues to fix.
Thanks for your time anyway.