Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.77
Broken: version: 2.90.0, branch: master (modified), commit date: 2020-08-31 11:26, hash: rB0330d1af29c0
Worked: Probably never
Short description of error
I have not seen this in a list of known limitations therefore I am reporting this as a bug:
Extrude manifold tends to produce non manifold geometry if extrusion crosses an edge loop, which is in conflict of what the name of the tool suggest. One vertex connected to both closed and open edges in this way is not considered manifold geometry and also goes against common sense expectation of what kind of result this tool should provide.
Resulting geometry qualifies as non-manifold even according to Blender's own operator to select non-manifold geometry:
Exact steps for others to reproduce the error
- Create the geometry similar to the one one in the video (Cube with 2 subdivision)
- Select corner face on top of the cube and extrude it down past one or more edge loops, as seen in the video
Result: Resulting produced geometry is non-manifold:
Expected: The tool produces manifold geometry, as the name suggests.