BMesh Operator "connect_vert_pairs" bug in special cases #112772

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Peng Yan · 2023-09-23T13:55:48+02:00

Peng Yan commented

2023-09-23 13:55:48 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.99

Blender Version
Broken: version: 4.0.0 Alpha, branch: dev_connect_vert (modified), commit date: 2023-09-22 16:42, hash: 9e6b6f31b8c0
Worked: (newest version of Blender that worked as expected)

Short description of error
When the connection line between vertex pairs passes through a concave vertex of a polygon, it may produce undesirable results, see the screenshots below.

Exact steps for others to reproduce the error

Create a mesh that contain a concave polygon.
Select the start point and end point, see fig1.

note that the concave vertex must exactly fall on the connection line between two input points (with distance less than 0.0001m).

perform Vertex/Connect Vertex Path or Vertex/Connect Vertex Pairs will generate unsatisfying results, for case1 see fig2:
Undo the connection, just move the concave point in x axis by 0.0001m (the CONNECT_EPS defined in bmo_connect_pair.cc), another awkward result (case2) will be produced by performing connection again. The path is not even continuous, see fig3:
in another similar example below, I move another point on the direction of connection line, this time, Blender gives the error message “Could not connect vertices”. This is case3, see fig4:

I also provide the .blend file here to reproduce these results.
I have written code to fix this bug, I'll make a pull request later.

For more detailed discussion of the cause and fix ideas, see this topic on Dev forum:
https://devtalk.blender.org/t/bug-report-and-proposed-fix-for-bmesh-operator-connect-vert-pairs-in-special-cases/31249?u=sayaka

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.99 **Blender Version** Broken: version: 4.0.0 Alpha, branch: dev_connect_vert (modified), commit date: 2023-09-22 16:42, hash: `9e6b6f31b8c0` Worked: (newest version of Blender that worked as expected) **Short description of error** When the connection line between vertex pairs passes through a concave vertex of a polygon, it may produce undesirable results, see the screenshots below. **Exact steps for others to reproduce the error** 1. Create a mesh that contain a concave polygon. 2. Select the start point and end point, see fig1. note that the concave vertex must exactly fall on the connection line between two input points (with distance less than 0.0001m). 3. perform Vertex/Connect Vertex Path or Vertex/Connect Vertex Pairs will generate unsatisfying results, for case1 see fig2: 4. Undo the connection, just move the concave point in x axis by 0.0001m (the CONNECT_EPS defined in bmo_connect_pair.cc), another awkward result (case2) will be produced by performing connection again. The path is not even continuous, see fig3: 5. in another similar example below, I move another point on the direction of connection line, this time, Blender gives the error message “Could not connect vertices”. This is case3, see fig4: I also provide the .blend file here to reproduce these results. I have written code to fix this bug, I'll make a pull request later. For more detailed discussion of the cause and fix ideas, see this topic on Dev forum: [https://devtalk.blender.org/t/bug-report-and-proposed-fix-for-bmesh-operator-connect-vert-pairs-in-special-cases/31249?u=sayaka](url)

fig1.png

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fig3.png

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test_connect_pair_3-5.blend

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fig2.png

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fig4.png

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