/** @return the previous QuadEdge (pointing to this.orig) */
public QuadEdge oprev() {
return rot.onext().rot();
}
/** @return the symetric (reverse) QuadEdge */
public QuadEdge sym() {
return rot.rot();
}
/** @return the symetric dual QuadEdge */
public QuadEdge rotSym() {
return rot.sym();
}
/**
* Test if the Point p is on the line porting the edge
*
* @param e QuadEdge
* @param p Point to test
* @return true/false
*/
public static boolean isOnLine(QuadEdge e, Point p) {
// test if the vector product is zero
if ((p.x - e.orig().x) * (p.y - e.dest().y) == (p.y - e.orig().y) * (p.x - e.dest().x))
return true;
return false;
}
/**
* Test if the Point p is at the right of the QuadEdge q.
*
* @param QuadEdge reference
* @param p Point to test
* @return true/false
*/
public static boolean isAtRightOf(QuadEdge q, Point p) {
return isCounterClockwise(p, q.dest(), q.orig());
}
/**
* Delete a QuadEdge
*
* @param q the QuadEdge to delete
*/
public static void deleteEdge(QuadEdge q) {
splice(q, q.oprev());
splice(q.sym(), q.sym().oprev());
}
public static void swapEdge(QuadEdge e) {
QuadEdge a = e.oprev();
QuadEdge b = e.sym().oprev();
splice(e, a);
splice(e.sym(), b);
splice(e, a.lnext());
splice(e.sym(), b.lnext());
e.orig = a.dest();
e.sym().orig = b.dest();
}
/**
* Create a new QuadEdge by connecting 2 QuadEdges
*
* @param e1,e2 the 2 QuadEdges to connect
* @return the new QuadEdge
*/
public static QuadEdge connect(QuadEdge e1, QuadEdge e2) {
QuadEdge q = makeEdge(e1.dest(), e2.orig());
splice(q, e1.lnext());
splice(q.sym(), e2);
return q;
}
/**
* 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);
}
/**
* 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;
}