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Bridge Edge Loops operation has inconsistent results
Confirmed, NormalPublicBUG

Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GT 730/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.50

Blender Version
Broken: version: 2.83 (sub 11), branch: master, commit date: 2020-03-28 20:40, hash: rBa24f52c51cff
Worked: N/A

Short description of error
Bridge Edge Loops operation result is different when mesh is duplicated in Edit Mode vs. duplicated in Object Mode and joined into one object.

Exact steps for others to reproduce the error

Works in default startup file.

  1. Add plane through Add > Mesh > Plane
  2. In Edit Mode duplicate it and move the duplicate a bit sideways (along X or Y axis)
  3. Select All vertices and go Edge > Bridge Edge Loops to connect them with an arch. Set Number of cuts to 2+.
  4. The resulting arch is weirdly 'cut' in the middle, introduces non-manifold faces and flipped normals.

No such issues occur when the original plane is duplicated in Object Mode and joined into one object. Only direct duplicating in Edit Mode causes this behavior.

Duplicated in Edit Mode. Gives weird results.

Duplicated in Object mode and joined. Creates a nice arch.

Thanks a lot for looking into this problem.

Event Timeline

The Bridge Edge Loop operator does not consider the average Normal of Faces. It just reads the edges loops.
So it makes no difference whether the edge loop has a face in it or if the normal is pointed to one side or the other of the face.
This is something that could improve, but it is not so simple to implement.

Thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as 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

@Germano Cavalcante (mano-wii) Thanks for you reply, but perhaps I didn't explain it well enough :).

Those flipped normals aren't the main issue, they're just one of the consequent problems.
The main issue is deformed geometry, and that happens no matter if the loops has a face or not, or if the normal is pointed up/down.

Please consider reopening the task, this doesn't look like intended behavior.

Germano Cavalcante (mano-wii) reopened this task as Needs Triage.Wed, May 13, 3:49 PM
Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Wed, May 13, 4:25 PM
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

It is indeed a bug.
A similar problem has been reported before and rB304501193be6 was supposed to have fixed it.