   How do I rotate a cube about one of its edges?
  I'm trying to rotate a cube about one of its edges -- specifically, an edge that is parallel to the x axis.  The cube should be rolling as if downhill, edge over edge over edge.The only way I can picture doing this is to do a standard x-axis rotation while the cube is centered at the origin, and then somehow calculate where the edge should lie when translating it back to its world position.Is there an easier way?  If not, how can I find that translation to get the edge where it needs to be?   
  Wow, I just realized how easy this is.  I feel dumb.Translate edge to x-axis.  Rotate.  Translate back by same amount.   