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Edge extrusion error MacOs
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System Information
Operating system: Darwin-17.4.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon RX 580 OpenGL Engine ATI Technologies Inc. 4.1 ATI-1.60.26

Blender Version
Broken: version: 2.80 (sub 74), branch: blender2.7, commit date: 2019-06-08 13:24, hash: rB81b68f7279cd
Worked: (optional)

Short description of error
edge extrusion from a pane or a Ngon creates an extra face within extruded region.

Exact steps for others to reproduce the error
Add a plane, go to edit mode, go to edge select, select edges, extrude out.

Add circle fill type ngon. go to edit mode, select edges, extrude out.

Attached file has a circle Ngon filled and a plain ready for extrusion as well as an example of an extruded plane and circle. Also note that the problem does not occur when the fill type for a circle is set to triangle fan.



Event Timeline

tom k (tomjk) added a subscriber: tom k (tomjk).EditedJun 9 2019, 12:34 PM

This is because selecting all edges around a face also selects that face, so the face is also extruded.
You can get the behaviour you want by hitting Alt+E (or go to 3d view header -> Mesh menu -> Extrude submenu) and choosing Extrude Edges.

Whether selecting all edges around a face in edge select mode should select the face is a question of design (and a good question too), but not a bug.

Yes I see what you mean, I had forgotten all about the extrude edge option. However, if I am extruding away from four selected lines, as in the case of a plain or multiple lines as in the case of an Ngon, why am I getting an extra face in between them. I should be getting a new face out ward from the direction of extrusion not a fill in between them as well. Also, why is this not happening if the original fill type of the circle is an triangle fan? In essence I am getting an extrusion and also filling a "new face" that I do not want. Does this happen in other design software? I only know blender, so I really have no idea if this is normal.

Sorry, but I think its a bug and not a feature. Maybe its just a really deep paper cut.

Blender doesn't know how to differentiate between extruding perpendicular to the surface and extruding in the plane of the surface. If it did, and automatically toggled the extra fill face, it would potentially break workflow for those who extrude then transform in two seperate steps. Blender can't foresee your intent, so you have to let it know by choosing a particular extrusion mode.

The reason why you don't have this problems with triangle fans comes from the rule about how selecting all edges around a face also selects the face. When you select the outer edge of the tri-fan circle, you only have 1 out of 3 of the edges of any face selected, so they remain unselected.

I don't know about other software, sorry :)

I see, that makes sense. Maybe then its not a bug? See what the judges say.
All, in all, you learn something new every day!