* Note that though presentation above is equilateral triangles, this
* is not the case. It's actually a square lattice with half of the
* diagonals added. We can't straighten it out because at the join
* the diagonals point the other way!
*
* Note that though presentation above is equilateral triangles, this
* is not the case. It's actually a square lattice with half of the
* diagonals added. We can't straighten it out because at the join
* the diagonals point the other way!
*