Unify Windings (Ngon) problem

The polygon lines shows the same direction regardless the usage of Unify Windings or not.UNIFY_WINDINGS_problem.gh (5.9 KB)

What are you actually trying to do here?
Your mesh doesn’t have any ngons - just triangles.
The triangle boundary directions already look consistent - counterclockwise around each face.

I think NGON should work for triangles as well. (N=3)
Unify windings "unifies polygon edge order so that every neighbor edge is flipped, similar to half-edge data-structure " :

Yes, your mesh looks like it already has unified face normals (and vertices of each face consistently oriented) before doing anything to it.
Therefore nothing changes when you apply this further ‘unify’ operation.

I thought it is actually reversing the actual state. It is logical for me.

Unifying is different from flipping.

If you want to reverse all the face windings you can flip a mesh like this

flipmesh.gh (12.7 KB)

Unifying would be for if you had some of the faces ordered inconsistently with the others.

Here you have flipped the face normal didnt you? But as far as I know Unify Windings just changing the polygon edge order without doing anything with the face normals. Maybe I am wrong.

The face normals are affected by the vertex ordering, so if you reverse the order, and calculate the face normals you will see that they flip:

facevert_order.gh (11.3 KB)

You can have the flipped NGon winding without considering mesh normals, if you do not want to follow initial mesh face vertex order. Rhino NGon class method boundaryVertexList has no relation to initial mesh face winding, just stores vertex index list.

Order.gh (18 KB)

But as Daniel is saying I am not sure why you need this especially for triangle faces?