Function orient2dVector

orient2dVector(a: VectorPoint, b: VectorPoint, c: VectorPoint): number
Check the orientation of c relative to the line through a and b
Parameters
- a: VectorPoint
  first point
- b: VectorPoint
  second point
- c: VectorPoint
  comparison point
Returns number
- a positive value if the points a, b, and c occur in counterclockwise order (c lies to the left of the directed line defined by points a and b).
- Returns a negative value if they occur in clockwise order (c lies to the right of the directed line ab).
- Returns zero if they are collinear.