# Extruding, other side does not have face

As you see in the picture, after extruding the bottom face, it seems to simply move up. There really is no bottom face now. Sorry if it's hard to understand. I need it to have two faces instead of one. One on the very bottom, and one where it's extruded. I know you can extrude the bottom edges and then merge them, but is there any easier way? I don't want the bottom face when I extrude it to be one-sided. I think Maya actually creates a new face.

Thanks!

• Could you add the steps? I can't reproduce the result everything works as expected. – stacker Jan 14 '14 at 21:21
• 1. Make a cube 2. Edge loop in half and take out a side. 3. Select bottom face and extrude upwards. I want a bottom face after extruding covering the very bottom. – Mustang37 Jan 14 '14 at 21:27
• May I ask, what is it that you are making? I can't understand your workflow clearly. – ikel Jan 14 '14 at 21:53

If you extrude a face connected to other faces, the extrusion will leave a hole.

But if you extrude a disconnected face, you will have a solid shape. If you press Y to disconnect the shape before extruding it, you will make it solid and have that bottom face.

EDIT: But, beware, if you do this, you will get weird geometry. Things might not be connected the way you want. I feel a little dirty, doing it. :)

• Could you clarify "I feel a little dirty, doing it."? It is because such practice is commonly shunned in the 3D community? – ikel Jan 14 '14 at 21:50
• It's not so much that the practice is shunned, as much as it is usually the wrong way to solve the problem, or it's accidental. Basically "if you press y...you will make it solid" is not exactly the way to make this shape solid, which is why it feels wrong. It also feels wrong because there are now 3 faces connected to the same edge (which is almost always a bad idea) and there is a section of geometry that's totally enclosed, therefore invisible, but still has to be rendered. – Matt Jan 14 '14 at 22:19
• @Gunslinger would you like some soap? – A Wild RolandiXor Feb 11 '15 at 22:44

If I understand what you are asking, the quickest way to do this is to select the face you want to extrude and duplicate it with ShiftD, next, don't deselect or select anything else but rather press E to extrude that face and adjust accordingly, finally, select the entire mesh with A run a W > Remove Doubles operation.

This is how extrude tool works.

From the wiki:

One tool of paramount importance for working with meshes is the Extrude tool. It allows you to create parallelepipeds from rectangles and cylinders from circles, as well as easily create such things as tree limbs. Extrude is one of the most frequently used modeling tools in Blender. It’s simple, straightforward, and easy to use, yet very powerful.

The selection is extruded along the common normal of selected faces. In every other case the extrusion can be limited to a single axis by specifying an axis (e.g. X to limit to the X axis or ⇧ ShiftX to the YZ plane. When extruding along the face normal, limiting movement to the global Z axis requires pressing Z twice, once to disable the face normal Z axis limit, and once to enable the global Z axis limit.

Although the process is quite intuitive, the principles behind Extrude are fairly elaborate as discussed below:

1. First, the algorithm determines the outside edge-loop of the extrude; that is, which among the selected edges will be changed into faces. By default (see below), the algorithm considers edges belonging to two or more selected faces as internal, and hence not part of the loop.
2. The edges in the edge-loop are then changed into faces.
3. If the edges in the edge-loop belong to only one face in the complete mesh, then all of the selected faces are duplicated and linked to the newly created faces. For example, rectangles will result in parallelepipeds during this stage.
4. In other cases, the selected faces are linked to the newly created faces but not duplicated. This prevents undesired faces from being retained “inside” the resulting mesh. This distinction is extremely important since it ensures the construction of consistently coherent, closed volumes at all times when using Extrude.
5. When extruding completely closed volumes (like e.g. a cube with all its six faces), extrusion results merely in a duplication, as the volume is duplicated, without any link to the original one.
6. Edges not belonging to selected faces, which form an “open” edge-loop, are duplicated and a new face is created between the new edge and the original one.
7. Single selected vertices which do not belong to selected edges are duplicated and a new edge is created between the two.

For a mesh to be able to exist in the real world, everything must have thickness. Generally speaking, it is a good idea to make your meshes work this way.

For example (using a cube), if you extrude the bottom face downwards, you can see it only creates four new faces around the edges:

The reason it does not create a new face for the bottom and leave the original bottom face is because you would then have a non-manifold mesh (not normally what you want):

To test a mesh you could use CtrlAltShiftM to select non-manifold geometry.

To get the shape I think you want you could inset (I) the one of the middle faces and then extrude it back. This will result in a manifold mesh:

• Nice read but I don't really see how this answers the question. – iKlsR Jan 14 '14 at 23:49
• @iKlsR Better now? – gandalf3 Jan 15 '14 at 0:21
• @iKlsR I believe it answers the question as for why it leaves hole underneath. Besides, gandalf3 mentioned about having thickness, which is crucial in extrusion without hole. – ikel Jan 15 '14 at 1:15

Probably the best way to make the shape you're going for is to:

• make a cube
• loop cut the middle (like you are already doing)
• loop cut again, but below the first cut
• delete one side face
• select the four interior vertices and make them a face (using f)
• I don't think OP is asking how to make a shape but rather how to have a persistent face after extruding. – iKlsR Jan 14 '14 at 22:29
• That's possible, but I was keying off this: "I need it to have two faces instead of one. One on the very bottom, and one where it's extruded. I know you can extrude the bottom edges and then merge them, but is there any easier way?" – Matt Jan 14 '14 at 22:54

There must be some subtle detail within the steps you described in your comment, lead to:

Add a cube, loop cut (horizontally) and a take a face out leads to:

Extruding the bottom face selected constrained to z-axis

Looks as expected:

If you have moved the bottom face upwards (z-axis) the overlapping face would have been painted a bit brighter, but only as long you don't continue editing.

• ...then move that face up on the z-axis. – Matt Jan 14 '14 at 22:23
• @Matt then you would stil have the white border and a visual feedback (brighter faces) that something is wrong. – stacker Jan 14 '14 at 22:26
• Quite right. Your next-to-last image is almost right. Your answer began by trying to recreate the OP's original shape, which you have now done. The OP apparently wants faces both where you placed that last one, and covering the bottom as well. – Matt Jan 14 '14 at 22:40
• @Matt Hmm, maybe, never needed it this way then you answer would match. However he should provide more details. – stacker Jan 14 '14 at 22:49
• Apologize if I didn't add more details. Gunslingers answer was perfect. Well, actually all of your answers were awesome! Thanks! – Mustang37 Jan 15 '14 at 2:29