--- tetrahedron2 :: Face -> Tetrahedron
--- tetrahedron2 f =
--- Tetrahedron c v0' v1' v2' v3'
--- where
--- c = cube f
--- v0' = v2 f
--- v1' = v3 f
--- v2' = center f
--- v3' = center c
-
-
--- tetrahedron3 :: Face -> Tetrahedron
--- tetrahedron3 f =
--- Tetrahedron c v0' v1' v2' v3'
--- where
--- c = cube f
--- v0' = v3 f
--- v1' = v0 f
--- v2' = center f
--- v3' = center c
-
--- tetrahedrons :: Cube -> [Tetrahedron]
--- tetrahedrons c =
--- concat [
--- [tetrahedron0 f0, tetrahedron1 f0, tetrahedron2 f0, tetrahedron3 f0],
--- [tetrahedron0 f1, tetrahedron1 f1, tetrahedron2 f1, tetrahedron3 f2],
--- [tetrahedron0 f2, tetrahedron1 f2, tetrahedron2 f2, tetrahedron3 f2],
--- [tetrahedron0 f3, tetrahedron1 f3, tetrahedron2 f3, tetrahedron3 f3],
--- [tetrahedron0 f4, tetrahedron1 f4, tetrahedron2 f4, tetrahedron3 f4],
--- [tetrahedron0 f5, tetrahedron1 f5, tetrahedron2 f5, tetrahedron3 f5] ]
--- where
--- f0 = face0 c
--- f1 = face1 c
--- f2 = face2 c
--- f3 = face3 c
--- f4 = face4 c
--- f5 = face5 c
+ -- | It's possible to implement this, but it hasn't been done
+ -- yet. A face will contain a point if the point lies in the same
+ -- plane as the vertices of the face, and if it falls on the
+ -- correct side of the four sides of the face.
+ contains_point _ _ = False