Triangulating a mesh with overlapping tri and quad faces can cause an assertion failure #93574

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Fen · 2021-12-02T15:28:23+01:00

Fen commented

2021-12-02 15:28:23 +01:00

System Information
Operating system: Windows-10-10.0.19042-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 472.12

Blender Version
Broken: version: 3.1.0 Alpha. Commit hash: 1620dcd208
Worked: Unsure

Short description of error
Triangulating a specific mesh in a specific object causes an assertion failure in the debug build.

Exact steps for others to reproduce the error
Without setup:

Open the triangulate-bug.blend file
Select Original and enter Edit Mode
Run the Triangulate Faces operator
Assert failure

Manual setup:

Open the triangulate-bug.blend file
Select DIY and enter Edit Mode
Add a plane, merge at center to get a single vertex
Duplicate three times to get four vertices
Select all of the vertices and fill, producing a quad
Select three of the vertices and fill, producing a tri
Select all of the vertices and run the Triangulate Faces operator
Assert failure

triangulate-bug.blend

Creating a brand-new object and following the same steps does not cause an assertion failure. However, using a copy of the object that caused the problem (even after deleting all of its vertices, which is how I made the DIY object) causes the assertion failure.

Just adding a plane to DIY in edit mode and adding a triangle face does not cause the assertion failure. However, if I delete the face (and only the face), then fill to create a quad, then fill to create a tri, the error happens.

I don't have any modifiers on the offending object, and I can't really tell if there's anything "special" about it. It has no constraints, vertex groups, materials, etc. etc.

This does not cause a crash in the release build.

BLI_assert failed: D:\blender-git\blender\source\blender\bmesh\intern\bmesh_mesh_normals.c:523, bm_mesh_loops_calc_normals_for_loop(), at '(bm->elem_index_dirty & (BM_FACE | BM_LOOP)) == 0'

Full error output: P2637

**System Information** Operating system: Windows-10-10.0.19042-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 472.12 **Blender Version** Broken: version: 3.1.0 Alpha. Commit hash: `1620dcd208` Worked: Unsure **Short description of error** Triangulating a specific mesh in a specific object causes an assertion failure in the debug build. **Exact steps for others to reproduce the error** Without setup: 1. Open the triangulate-bug.blend file 2. Select *Original* and enter Edit Mode 3. Run the *Triangulate Faces* operator 4. Assert failure Manual setup: 1. Open the triangulate-bug.blend file 2. Select *DIY* and enter Edit Mode 3. Add a plane, merge at center to get a single vertex 4. Duplicate three times to get four vertices 5. Select all of the vertices and fill, producing a quad 6. Select three of the vertices and fill, producing a tri 7. Select all of the vertices and run the *Triangulate Faces* operator 8. Assert failure ![image.png](https://archive.blender.org/developer/F12679799/image.png) [triangulate-bug.blend](https://archive.blender.org/developer/F12679771/triangulate-bug.blend) Creating a *brand-new object* and following the same steps does not cause an assertion failure. However, using a copy of the object that caused the problem (even after deleting *all of its vertices*, which is how I made the *DIY* object) causes the assertion failure. Just adding a plane to *DIY* in edit mode and adding a triangle face does not cause the assertion failure. However, if I delete the face (and only the face), then fill to create a quad, then fill to create a tri, the error happens. I don't have any modifiers on the offending object, and I can't really tell if there's anything "special" about it. It has no constraints, vertex groups, materials, etc. etc. This does not cause a crash in the release build. `BLI_assert failed: D:\blender-git\blender\source\blender\bmesh\intern\bmesh_mesh_normals.c:523, bm_mesh_loops_calc_normals_for_loop(), at '(bm->elem_index_dirty & (BM_FACE | BM_LOOP)) == 0'` Full error output: [P2637](https://archive.blender.org/developer/P2637.txt)

Fen commented

2021-12-02 15:28:23 +01:00

Added subscriber: @chemicalcrux