Why can't I use Loop Cut on certain parts of my mesh?

Question

This is a recurrent issue for me and it's been bothering me for quite some time.

I can't seem to add vertices with Ctrl+R on some faces on my meshes, and it's always the faces which I have filled in with F.

Here's an example, in which I have extruded my mesh into four directions and then filled in the corners, making an octagon, but I cannot add vertices to the corners, or the faces that are "open":

I am using version 2.72b, on a Mac.

Related - http://blender.stackexchange.com/questions/17870/loop-cut-wont-go-all-the-way-around and http://blender.stackexchange.com/questions/15126/loop-cut-entirely-after-dissolving-an-edge. — Mr Zak, Jun 19 '16 at 20:23

Demons Fate · Answer 1 · 2016-06-20T07:14:01.763

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if you fill faces with not exactly 4 vertices, blender does not know where to place the loop cut (ctrl + r). you need to convert your ngons to normal quad faces if you want to use loop cuts.

edited Jun 20 '16 at 07:14

answered Jun 19 '16 at 17:53

Demons Fate

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score 5 · Answer 2 · answered Jun 20 '16 at 14:24

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One workflow that might work for you is to select all the edges that you want to cut and use the "subdivide" operator ( w ).

answered Jun 20 '16 at 14:24

Mutant Bob

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score 4 · Accepted Answer · edited Apr 13 '17 at 12:57

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You can only loop cut through quadrilateral faces in a line, like a row of rectangles. A loop cut through a triangle would divide one of the vertices, but that can't happen. N-gons also don't work well with it. See Anthony Forwood's comment:

Quads are ideal, tris when necessary, and ngons only when absolutely necessary.

It has nothing to do with the F function.

edited Apr 13 '17 at 12:57

Community

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answered Jun 19 '16 at 17:50

Shady Puck

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They don't have a triangle, they have an n-gon. – Ray Mairlot Jun 19 '16 at 18:05
@RayMairlot I'm sorry, but I don't understand what you mean. Can you clarify? – Shady Puck Jun 19 '16 at 18:10
An ngon has more than four sides, and Blender doesn't like them much. – Anthony Forwood Jun 19 '16 at 22:34
@AnthonyForwood Ah, that makes sense. Thank you very much for clarifying. I agree. – Shady Puck Jun 19 '16 at 23:00
Keep it in mind when working on meshes. Quads are ideal, tris when necessary, and ngons only when absolutely necessary. – Anthony Forwood Jun 20 '16 at 00:24
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It's not that blender "doesn't like" non-quads. It is just that a lot of cliches only work for quads and when you try to apply them to triangles and ngons, the rules do not apply. Edge Loop is one of those. – Mutant Bob Jun 20 '16 at 14:17

score 0 · Answer 4 · answered Mar 10 '19 at 01:00

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You can try editing the vertices, by creating Quads, select the vertices you need to join and select the vertice menu, then select connect vertice pairs, this should solve the problem

answered Mar 10 '19 at 01:00

Matthew E

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Why can't I use Loop Cut on certain parts of my mesh?

4 Answers4