Calculate what points are on the right side of a line and on the left side of the same line

[Thomas_Mahon]

You could try something like this. The last post in the thread has an example graph of this solution:

What side of a curve point is on

Project each point into the curve (nearest/tangent) and store the vector of the projection. Get the tangent on the curve at the projected point. Compute the cross product of the two vectors. Now compute the dot of this vector against the global Z axis. The scalars which are positive will identify all the points on the right side of the curve, negative are the ones on the left side.