How to find points "clockwise" relative to origin?

[rachil0]

I gave it some more thought, and I think you can avoid the winding/overflow issues by minimizing the dot product over the pairs which have positive cross product. New pseudocode:

Number smallest_dot = 1.0;
Array[2] best_vertex_pair;
for (a = first vertex to last)
  for (b = first vertex to last)
     if (a != b && cross2D(a,b) > 0)
       {
       Number current_dot = dot2D( normalize(a), normalize(b) );
       if (current_dot < smallest_dot)
         { smallest_dot = current_dot; best_vertex_pair = [a,b]; }
       }