PolyStrips: Crash when creating corner while merging into existing geometry

[jlampel]

Blender can fully crash if you draw a strip with a corner onto another strip. Here are some examples, one in Blender 4.3 and one in Blender 4.4:

RFCore.register
RFCore_Operator.__init__
CACHING BVHS FOR ALL SOURCE OBJECTS
  0.00secs
RFCore_Operator executing
Activating <class 'bl_ext.vscode_development.retopoflow.retopoflow.rfoverlays.quadstrip_selection_overlay.RFOperator_PolyStrips_Selection_Overlay'>
<bpy_struct, Area at 0x00000282EFEE6880> <bpy_struct, Region at 0x00000282EFEEBC20>
RFOperator_PolyStrips_Insert.execute: Caught Exception division by zero
____________________________________________________________________________________________________
Exception Info
- Time: 2025-04-01 19:56:25.895832
- Count: 1
- Hash: 96d54cf4e057eb721689d9195ab845e8
- Info:
  - EXCEPTION (<class 'ZeroDivisionError'>): division by zero
  -     C:\Users\Jonathan\AppData\Roaming\Blender Foundation\Blender\4.3\extensions\vscode_development\retopoflow\retopoflow\rftool_polystrips\polystrips_logic.py
  - 000 0341:<listcomp>() find_point_at(stroke3D_local, self.is_cycle, (i / (nsamples - 1)))
  - 001 0340:create() samples = [
  -     C:\Users\Jonathan\AppData\Roaming\Blender Foundation\Blender\4.3\extensions\vscode_development\retopoflow\retopoflow\rftool_polystrips\polystrips.py
  - 002 0227:execute() logic.create(context)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error   : EXCEPTION_ACCESS_VIOLATION
Address : 0x00007FF7AFFE960F
Module  : blender.exe
Thread  : 000259f0
Writing: C:\Users\Jonathan\AppData\Local\Temp\blender.crash.txt

[vxlcoder]

should work now!

[jlampel]

This is much better! There are no longer issues with the above stroke shapes. I can still get a crash, but it is in an extremely specific scenario. It happens when you make this exact shape, where the stroke connects to one quad but ends on the one next to it:

If you end the stroke on any other quad, it does not occur. It's a nonsense shape that I don't think anyone would make on purpose, but it could still happen.

[jlampel]

This appears to be fixed now! I think in 1f9dbe8

[jlampel]

Whoops, sorry, that was a little premature. I didn't trigger it after several attempts, saw a PS change, and figured it was good. But I can still cause the crash after enough tries.