CheckOutwardNormals

Checks face/vertex list of closed triangulated objects to make sure all normals are outward facing.

Checks normals are outward facing and re-orders face if not.

Works with concave objects and with cavities. e.g. swiss cheese

Only works with triangular faces

Requirements: Function TriangleRayIntersection by Jarek Tuszynski

https://www.mathworks.com/matlabcentral/fileexchange/33073-triangle-ray-intersection

Input: faces, F (Nx3)

vertices, V (Nx3)

Output: corrected face list so all normals are outwards facing

list of any faces reordered

Assumptions: Normals are from clockwise orientation of faces. I.e. Right hand rule

Shape is closed and watertight.

No duplicate faces

Potential improvements: TriangleRayIntersection accepts multi-face, multi-ray input so should be able to speed up by removing the loop over the faces.