For most Streaming Motion, you can use ElementID to determine where you are within a point set. ElementID 5 = Point 5. Element ID will match the point you provided. Streaming Motion using RSIMotionTypeBESSEL, RSIMotionTypeBSPLINE, and RSIMotionTypeBSPLINE2 involved carrying forward 1 point (Bessel, Bspline2) or 2 points (Bspline). It needs to do this for motion calculations.