Loop Cuts

What is a Loop Cut in Blender for ?

A Loop Cut is defined as splitting a loop of adjacent faces down the middle. If that doesn’t make sense, let me demonstrate with our trusty cube. I have selected a closed-loop of faces – the left, top, right and bottom faces. The face at the back and the one nearest us are not selected. The other four that are selected are adjacent (sharing an edge) to one another and form a loop :

Cube-loop selected
Closed Loop of Faces Selected

Now start the Loop Cut tool by typing Ctrl KeyR Key. (It doesn’t matter whether the loop is selected or not)

Move the cursor close to a face, and a yellow ring will appear, indicating where the loop of faces will be cut in two. Move the cursor to the point shown, the new looped ring of edges will appear:

Cube-Single loop cut
Loop cut appears

Left-click Left-Click and nothing seems to happen until you move the mouse. With the mouse moving, you can now define where the new loop will appear by left-clicking Left-Click . If you want the Loop Cut to be precisely in the middle, press Esc key first and then left-click Left-Click to lock in its position and complete the operation:

Completed Loop Cut
Completed Loop Cut

If you try the procedure again you can put another loop cut either “behind” the first Loop Cut or “in front” of it:

Second Loop Cut
Second Loop Cut

For more info on Loop Cuts, here is a link to the Blender Manual

There’s always a Potential Problem!

Sometimes a Loop Cut appears not to work or only partially. Let’s bevel (click here to read about bevelling) the vertical edge of the cube nearest to us:

Add bevel
4-segment bevel added to vertical edge

Now let’s add a loop cut Ctrl KeyR Keyon the front half of the Cube:

One Edge only
Only one segment is possible

And we see that the loop refuses to run right around the cube. Blender can only give us a single edge when we click in the vicinity of the white cross. Why won’t it go around in a loop? This problem annoys many modellers, especially if they don’t understand what is going on. There is a basic rule with loop cuts. “A loop cut can only travel through quads”. The moment the loop cut tool encounters either an Ngon or a Triangular face, it stops. So look carefully at the cube here:

Ngon above and below
The selected Ngons stop the Loop Cut tool and so only one single edge is possible

So, if your Loop Cut doesn’t want to make a complete loop, look for an Ngon or a Tri blocking its path.

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