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I am trying to extrude some face inwards (the opposite of extruding outwards). In this screenshot you can see that I have selected the faces:

enter image description here

In the next screenshot can you see that I was actually able to intrude the faces, but the outer vertices stay where they are: enter image description here

Does anybody know why this happens and how to avoid it? Thank you!

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Yes, it does.

Extruding in 3D modeling means something like:

to shift a selection in space while creating all the geometry that is needed to keep all the non-selected parts in place

You can have more detailed information about how tha algorithm works in the official manual page.


Let's consider a UV sphere:

enter image description here enter image description here

Notice how in the example above the non selected faces keep their positions (and so their edges and vertices). Is something different from grabbing, as involves the creation of new geometry.

enter image description here enter image description here

By extruding, for example, along the normal axis, you may see from the pictures above how the operation does the same thing. In both cases (positive and negative normal axis extrusion) the surrounding vertices of the initial selection geometry keep their position.


One way to achieve the result you want is to extrude inward and than dissolve the starting geometry.

enter image description here enter image description here

After inward extrusion, assign the selected faces to a vertex group, than extend the selection with Ctrl++. Than that go to Vertex groups and remove previuosly assinged vertex group from the selection.

enter image description here

Press X to open the "Delete" menue and choose "Dissolve edges".

enter image description here

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I think you want to combine an extrusion (or intrusion) on 1 side and a simple grab on the other side. I think you can solve this using an edge loop and grab.
Start adding an edge loop with Ctrl+R then left click and move it (with mouse) left until it sticks the other edge loop.
enter image description here
enter image description here

Now go in face selection mode (1) and select "normal" as transform orientation (2)
enter image description here

Now you can select the faces and grab them with G,Z,Z. This allows you to move faces along their normal Z axis (as a simple extrusion does).
enter image description here

You also have to clean your mesh before doing this, you have already created empty faces that will make your life harder :
enter image description here
Select all with A, hit W and click "remove doubles" to clean your empty faces (probably resulting of previous extrusion attempts)

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  • $\begingroup$ Bithur, red text on grey background can be difficult to read, especially with the level of artifacts introduced in your image, can you redo them? $\endgroup$ – zeffii Aug 4 '15 at 19:51

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