Ok, so I have 10 control points for a 3 order bezier triangle. It is arbitrary which points are which, I know who they are and how to use them, but there is no obvious relation to these points from the edges to tessellate. In my hull shader, I decide how much to tessellate each of the three edges, but how do I know which edge is edge zero, one, two etc?

For example, if cp[0], cp[1] and cp[2] are the control points to my bezier triangle corners, how do I decide how much to tessellate each edge based on the screen size of the edge?