/**
* Create a new edge (i.e. a segment)
*
* @param orig origin of the segment
* @param dest end of the segment
* @return the QuadEdge of the origin point
*/
public static QuadEdge makeEdge(Point orig, Point dest) {
QuadEdge q0 = new QuadEdge(null, null, orig);
QuadEdge q1 = new QuadEdge(null, null, null);
QuadEdge q2 = new QuadEdge(null, null, dest);
QuadEdge q3 = new QuadEdge(null, null, null);
// create the segment
q0.onext = q0;
q2.onext = q2; // lonely segment: no "next" quadedge
q1.onext = q3;
q3.onext = q1; // in the dual: 2 communicating facets
// dual switch
q0.rot = q1;
q1.rot = q2;
q2.rot = q3;
q3.rot = q0;
return q0;
}
/**
* attach/detach the two edges = combine/split the two rings in the dual space
*
* @param q1,q2 the 2 QuadEdge to attach/detach
*/
public static void splice(QuadEdge a, QuadEdge b) {
QuadEdge alpha = a.onext().rot();
QuadEdge beta = b.onext().rot();
QuadEdge t1 = b.onext();
QuadEdge t2 = a.onext();
QuadEdge t3 = beta.onext();
QuadEdge t4 = alpha.onext();
a.setOnext(t1);
b.setOnext(t2);
alpha.setOnext(t3);
beta.setOnext(t4);
}
/** @return the previous QuadEdge (pointing to this.orig) */
public QuadEdge oprev() {
return rot.onext().rot();
}