Divide a cube only on front & back?


I’ve had this problem quite a few times now.

I’d like to create a 3d-rectangle and divide the front and back faces but not the sides, or at least no more than necessary. At the moment i can tell Blender to sub-divide a cube and it does that very well, problem is the program also creates little sub-divisions along the sides of the rectangle.

I’m sure i’m just being stupid. There must be a way you can do that, but at the moment i have to manage without it because i can’t find it.

Anybody help?

If you select edges only (switch to edge selection with Control Tab), you’ll get what you want. Only select the ones that you want subdivided (make sure you do all of them at the same time, or you’ll get funky triangles). Blender subdivides all of them when you are in vertex select mode because it also selects all the edges that the vertices you selected define.

Hopefully this makes sense, if not I can post a screenshot of which ones to select.

Well… Blender doesn’t allow N-gons. So what you want to do would crate a lot of 5, or 6, sided faces. And blender just won’t do that.

Now if you want to cut only a certain face, just select that and hit the K Key, then use Knife Exact. Then start above the cube, click, MMB while going down to enable the z axis (or hit the Z key) then drag till you are far below the cube. Hit ok and it will cut only the selected faces. But that will make triangles cause it can’t make N-gons.

The only say to make sure there aren’t any N-gons is to make two separate objects that are seamless but aren’t connected. It isn’t the best idea but if it isn’t moving and it is simple enough it might work. Hope that was clear :slight_smile:

Create a cube.
In edit mode, select a side face and extrude 2 units.
In object mode, scale Y and Z axes by 2.

Dudebot’s right. But, he didn’t mention that Blender has a near imitation of N-gons: F-gons. Or at least I heard it was a near imitation, I’ve never worked with N-gons, but it’ll fit your needs. Just select two or more faces and hit F, then select make F-gon and see what happens. :slight_smile:

Or you could just model it.

Delete the four faces that make the body of the mesh.
Subdivide the two ends to your desired level.
Select four vertices that make up an empty face you deleted.
Press F to make a face.
Repeat this for all the faces that make up the body.
It’s called Modeling.


Thanks for your help guys. It’s handy to know these techniques. I found Egan’s technique of selecting the edges-only with CTRL-TAB and then extruding those food for thought, as was as was ManOfSteel’s suggestion of selecting a side and extruding 2-units – the same maybe? i’m still working this out, a beginner to be sure…

I think definitely Egan’s will work, not sure what ManOfSteel means by ‘extruding 2 units’ though, but i feel Egan’s selecting an edge and extruding it could be something.

I also found that it’s easier to just forget about Cube and make a plane which you subdivide how you want, and then SHIFT-D duplicate and then manually make faces between them seemed to do the job. Hard to tell whether Egan’s or this technique would be quicker, maybe it depends on whether you like making faces of extruding better?

Maybe i’ll give Egan’s a go sometime and see.

Thanks guys,

Cubes in Blender have a side length (or edge) of 2 Blender Units by default.
By extruding 2 units (i.e. press E, then 2), you’re in fact creating the second half of your final cube. Then when you scale by 2 units too, you get a perfect cube with all sides equal to 4.

Hi ManOfSteel,

To be honest, I never realised there were anything like ‘Blender Units’, that’s why i didn’t know what you meant by ‘select the side of a face and extrude 2 units’. Obviously if a side of a cube is exactly 2 then you would want to do this, assuming Blender always creates the same size cube each time, which sounds like it does. Thanks a lot for your help mate, you’ve been useful and i’m grateful to you. Pablo.

Errrr, that method will result in a mesh with gaps in it. If you subsurf it you will notice very ugly deformations. Or if you use softbodies your mesh will fall apart in a weird way!

Yes, It will.
For straight line modeling it suffices.
Using this tech.I can easily cut a door or window.
For Organics, sure, this does not work.