Normal Flip

[seed93]

While unify_face_orientations can unify face orientations, it operates only within each connected component. As a result, an entire component may still have its normals flipped.

[JeffreyXiang]

This works as expected, since the function uses DSU to align all faces within a connected component to the triangle with the smallest index in that component.

To improve this, we could allow the function to be called with a reference direction, so that all faces in the component are aligned consistently with that direction rather than implicitly using the smallest-index triangle.