# Calculate surface area and outward normal of each face(non-planar) for a irregular hexahedron.

I am using the vector cross product to calculate each surface area and thus the outward normal. However, this approach fails when the surfaces are non-planar. So what is the best approach to calculate surface area and normal for a non-planar face of a hexahedron?

• BTW, if the edges are straight segments, then it's likely your hexahedron is in fact an irregular dodecahedron. Just turn the quadrangles into pairs of triangles.
– SF.
Dec 5 '18 at 16:58