This example shows how sharp lighting edges can be created through the
duplication of vertices.  Two cubes are drawn side by side, lit by the same
single point light (represented by a 3D plus sign icon in the scene).  The
cube on the left uses only 8 vertices, sharing them across each coincident
face.  As a result, while the geometry clearly approximates a cube, the smooth
lighting edges and shared normals cause the lighting to more closely represent
a poorly-tesselated sphere.  The cube on the right uses sharp geometric edges
and per-facet, per-vertex normals.  While this requires significantly more
vertices to create the cube, the effect of a sharp-edged cube is more 
convincing.

The key commands are:

i, k - translate light in x
j, l - translate light in y
Space - reset transforms
