How to remove interior faces while keeping exterior faces untouched?

This solution worked fine for my problem to remove interior faces

1. Switch to Vertex select.
2. Select all.
3. Vertex> Merge Vertices> By Distance (Remove doubles).
4. Select> Select all by Trait> Non Manifold (only check Vertices).
5. Switch to Face select.
6. Delete faces.

I think things have improved now or there is a better way.

Select -> Select Non Manifold (ctrl-shift-alt-m), then Select -> Select Inverse

Here are the steps that worked for me, at least in the simple case.

WARNING This does not technically remove "interior faces," it removes duplicate faces that exist in the same place, on meshes with poor initial topology.

Here's my mesh in solid view, to show the overall topology:

Inside we can see all the cube faces are made up of triangles that point in different directions, but still there's lots of interior faces I don't want:

1. Merge duplicate vertices

You may not have to do this, but the way my mesh is constructed of cubes, I have to.

• Go into edit mode > Vertices
• Press Ctrl+v d to delete duplicate vertices. Or Use this menu:

If this worked, you will see something like at the top of the screen.

2. Clean up faces with "Limited Dissolve"

• Go into Face mode
• Select all faces by pressing a
• Run limited disolve (there is no keyboard shortcut for this). It's found under Mesh > Clean Up > Limited Dissolve

The new topology uses quads now instead of triangles:

3. Remove interior faces

Only after completing the above steps did "select interior faces" work for me.

• Deselect all faces by pressing a
• Select interior faces (there is no keyboard shortcut for this) with Select > Select All by Trait > Interior Faces

Now your overlapping faces are selected, and you can delete them!

See also this answer to my other question about how to do this automatically in a script, which improves on this answer using raytracing.

A faster way to create minecraft models is to use the Remesh modifier with 'blocks' type.

It may not be the super fast method, but in case of huge objects it could be useful.

1. Delete interior faces (Select--> Interior Faces).
2. Select the whole object and choose (Mesh--> Clean up--> Fill Holes)
3. Select the whole mesh, unwrap it using 'Smart UV Project' and click the 'sync button'. Now select the parts which are the ngons.
4. Press Shift+H to see only selected parts in 3d view. Fill the gaps extruding edges with snap tool enabled. Use Shift+ R to fasten the process.

Update, this is working in Blender 2.81 (see: T68401)

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Use the following steps:

• Enter Editmode
• Set the Selection type to Faces
• Select all
• Vertices -> Merge -> By Distance
• Deselect all
• Select -> Select All by Trait -> Interior Faces
• Delete

You say Select -> Select All by Trait -> Interior Faces didn't work; I expect it's because you didn't remove doubles first.

Tip

After this, try Limited Dissolve, it gets rid of redundant geometry which can be useful in examples like this (if you don't have UV's or per-face materials set differently on each face).

This is actually quite simple, switch to Face select, select everything and then using MMB and making sure Limit Selection to Visible is ticked (this prevents any face not being from being selected), orbit around the model and deselect all outer faces, then use X to delete the inner faces.

Limit selection to visible.
Use circle or border select to select all the faces you can see.
Rotate the mesh and do the circle or border select again.
Repeat until all exterior faces are selected.
Invert selection.
Delete faces.