# Finding faces that are twisted wrong-side out relative to their neighbors?

How do I find faces that are twisted relative to their neighbors such that they face in while their neighbors face out?

I'm not talking about situations that can be resolved with Mesh / Normals / Recalculate Outside. I mean situations where e.g. faces are folded over one another such that it's simply not possible to resolve their orientation manually (see example below).

This object actually has lots of such faces. With Face Orientation it's easy to spot a lot of them but many of them are very small and so difficult to find visually.

Here, I've taken a bit of the object with two problem areas:

If you look closely, there's a red face up and to the right of the center and one down and to the left of the center (the second is much more obvious if looking from the other side).

If we look at the top-right one close-up we see the geometry is a complete mess:

I don't want to go too into it, as it's not the focus of my question, but we've got a large triangle T1 (v1, v2 and v3), it joins to T2 (v2, v3 and v4) along edge e1. T2 is folded back over T1 (hence the red color) and v4 is slightly raised off the surface of T1. T2 is joined to T3 (v2, v4 and v5) along e2. T3 folds back underneath T2 (so it's blue again). Finally, T3 is joined to T4 (v3, v4 and v5) along e3.

So how do I spot such pathological cases on a surface where almost all the faces are facing the right way? I.e. how do I spot tiny points of red on a surface that's almost completely blue?

Perhaps it's another question - but any heuristics for how to resolve such situations would also be appreciated.

The .blend file for the full object above is rather large but I've cut out the subsection shown above and you can find it here.