* ditch has 3 sides high and one low
* point has 1 side high and three low

This adds to the two versions already present:

* slope has 2 sides high and 2 sides low
* cube is just a cube (4 sides high)

* The planes and cube are from first priciples so probably don't follow
  best practice with regards to ordering
* Renderer includes some matrixes for testing (spin objects, fixed prespective)
* Model renderer uses backface culling (to check winding order of
  polygons