How to remove interior faces while keeping exterior faces untouched? I built something Minecraft style model by cubes. Now I met a problem: when I'm trying to remove all interior faces, it appears that some exterior faces are influenced inevitably. I wonder if there is some better way to do it better.



P.S.: There are three things I've tried:


Non-manifold checking (Ctrl Shift Alt M)
Select Interior Faces (Select -> Interior Faces)
3D Print Toolbox (Addon)


I didn't work it out so far, which leaves me no choice but manually deselect those faces I didn't want to remove, which takes quite a bit time for other cases.



There are answers like this Merge touching faces on model. But I don't think it works exactly in my case.





EDIT: Is there any faster way than enabling Limited Selection to Visible then manually deselect them from different views? (it will not work effectively in complex cases that require similar need)
Update, this is working in Blender 2.81 (see: T68401)



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).