proj_p1 = POINT_TO_PLANE(p1,p2,p3,p4) projects marker p1 into a plane defined by p2, p3, p4 ARGUMENTS p1 : n x 3 array Point to be projected onto a plane p2, p3, p4 : n x 3 arrays defining a plane RETURNS proj_p : p1 projected orthogonally onto the plane of p2, p3, and p4