The COMPUTE_MESH_NORMALS function computes normal vectors for a set of polygons described by the input array.
Result = COMPUTE_MESH_NORMALS( fVerts[, iConn] )
Returns a 3 x M array containing a unit normal for each vertex in the input array.
A 3 x M array of vertices.
A connectivity array (see the POLYGONS keyword to IDLgrPolygon::Init). If no iConn array is provided, it is assumed that the vertices in fVerts constitute a single polygon.