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Maniphest T87863

Mesh bisect can make face disappear
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Description

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: Quadro RTX 3000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 452.69

Blender Version
Broken: version: 2.93.0 Beta, branch: master, commit date: 2021-04-26 22:01, hash: rB14b26fc97659
Worked: None ? Same problem in various versions (2.83, 2.92)

Short description of error
When applying a bisect, it sometimes fail to cut a face crossed by the plane - the face disappears from the mesh.
Changing the Axis Threshold seem to change this behaviour.

Exact steps for others to reproduce the error

  • Open the attached blend file.
  • Select Mesh / Bisect operation
  • Draw some vectical line to start the operation
  • Then change the input values with :
    • Plane Point : 0.15m, 0, 0
    • Plane Normal : -1, 0, 0
    • Clear outer : enabled
  • The face disappears
  • Change the Axis Threshold value to 0.0 to have the face re-appear

bisect_bug3.blend592 KBDownload

Edit: added more complex test with mirror + bisect

bisect_bug3_complex.blend654 KBDownload

Revisions and Commits

rB Blender
rB0b61b7515126 Fix T87863: Bisect fails when edges of an N-gon lie on the plane
rBd31d5523d53f Fix T87863: Bisect fails when edges of an N-gon lie on the plane

Related Objects

Event Timeline

Nicolas Lelong (rotoglup) created this task.Apr 27 2021, 5:13 PM
Himanshi Kalra (calra) changed the task status from Needs Triage to Confirmed.Apr 27 2021, 9:24 PM
Himanshi Kalra (calra) added a project: Modeling.
Himanshi Kalra (calra) changed the subtype of this task from "Report" to "Bug".
Himanshi Kalra (calra) added a subscriber: Himanshi Kalra (calra).

I can confirm this on Windows 10.
Thanks for the report.

It looks like a floating point error with threshold.
Default threshold value is 0.0001, manually retyping it to 0.0 fixes the issue as told by OP

Pratik Borhade (PratikPB2123) added a subscriber: Pratik Borhade (PratikPB2123).Apr 28 2021, 3:23 AM

Can reproduce with attached file but not able to reproduce even with a simple cube mesh

Campbell Barton (campbellbarton) updated the task description. (Show Details)Apr 29 2021, 8:03 AM
Campbell Barton (campbellbarton) closed this task as Resolved by committing rBd31d5523d53f: Fix T87863: Bisect fails when edges of an N-gon lie on the plane.Apr 29 2021, 8:16 AM
Campbell Barton (campbellbarton) claimed this task.
Campbell Barton (campbellbarton) added a commit: rBd31d5523d53f: Fix T87863: Bisect fails when edges of an N-gon lie on the plane.
Himanshi Kalra (calra) mentioned this in T84999: Add Operator tests.Apr 29 2021, 9:19 AM
Jeroen Bakker (jbakker) mentioned this in T77348: Blender LTS: Maintenance Task 2.83.May 7 2021, 7:55 AM
Jeroen Bakker (jbakker) added a commit: rB0b61b7515126: Fix T87863: Bisect fails when edges of an N-gon lie on the plane.May 7 2021, 7:58 AM