/** Inserts point p in face c. Face c is split into 3 triangles. */
public TriangulationDSVertex_2<X> insertInTriangle(X p, TriangulationDSFace_2<X> t) {
if (t == null) throw new Error("Trying to star a null cell");
TriangulationDSFace_2<X> f1 = t.neighbor(1);
TriangulationDSFace_2<X> f2 = t.neighbor(2);
TriangulationDSFace_2<X> f0 = t.neighbor(0);
TriangulationDSVertex_2<X> v0 = t.vertex(0);
TriangulationDSVertex_2<X> v1 = t.vertex(1);
TriangulationDSVertex_2<X> v2 = t.vertex(2);
// create new vertex
TriangulationDSVertex_2<X> v = new TriangulationDSVertex_2<X>(p);
vertices.add(v);
// create and set two new faces
TriangulationDSFace_2<X> newFace2 = createFace(v0, v1, v, t, null, f2);
TriangulationDSFace_2<X> newFace1 = createFace(v0, v, v2, t, f1, newFace2);
newFace2.setNeighbor(1, newFace1);
// set new vertex and neighbors of old triangle
t.setVertex(0, v);
t.setNeighbor(1, newFace1);
t.setNeighbor(2, newFace2);
// set the faces incident to v and v0
v.setFace(t);
v0.setFace(newFace1);
// restore the marks of the initial triangle edges
for (int i = 0; i < 3; i++) t.unmark(i);
if (t.neighbor(0) != null) {
HalfedgeHandle<X> e = new HalfedgeHandle<X>(t, 0);
e.setMark(e.getOpposite().isMarked());
}
if (newFace1.neighbor(1) != null) {
HalfedgeHandle<X> e = new HalfedgeHandle<X>(newFace1, 1);
e.setMark(e.getOpposite().isMarked());
}
if (newFace2.neighbor(2) != null) {
HalfedgeHandle<X> e = new HalfedgeHandle<X>(newFace2, 2);
e.setMark(e.getOpposite().isMarked());
}
// return the new vertex
return v;
}
/**
* checks whether an edge is shared by two faces f1 and f2: the function check whether the
* corresponding vertices appear both in f1 and f2, in the correct order. LCA: a' tester
*/
public boolean areEqual(
TriangulationDSFace_2<X> face1, int i1, TriangulationDSFace_2<X> face2, int i2) {
HalfedgeHandle<X> edge1 = new HalfedgeHandle<X>(face1, i1);
HalfedgeHandle<X> edge2 = new HalfedgeHandle<X>(face2, i2);
TriangulationDSVertex_2<X> v1 = edge1.getVertex(0); // first vertex of edge1
TriangulationDSVertex_2<X> v2 = edge1.getVertex(1); // second vertex of edge1
boolean contained = edge2.hasVertex(v1);
if (contained == false) return false;
contained = edge2.hasVertex(v2);
if (contained == false) return false;
if (v1.equals(edge2.getVertex(0))) return false;
return true;
}
/** flips an edge in the triangulation and returns the new edge */
public HalfedgeHandle<X> flipEdge(HalfedgeHandle<X> e) {
TriangulationDSFace_2<X> f1 = e.getFace();
TriangulationDSFace_2<X> f2 = e.getOpposite().getFace();
// retrieve vertices of quadrangle
ArrayList<TriangulationDSVertex_2<X>> vert = new ArrayList<TriangulationDSVertex_2<X>>();
vert.add(f1.vertex(e.index()));
vert.add(f1.vertex((e.index() + 1) % 3));
vert.add(f2.vertex(e.getOpposite().index()));
vert.add(f1.vertex((e.index() + 2) % 3));
// retrieve neighboring faces of quadrangle
ArrayList<TriangulationDSFace_2<X>> neighb = new ArrayList<TriangulationDSFace_2<X>>();
neighb.add(f1.neighbor((e.index() + 2) % 3));
neighb.add(f2.neighbor((e.getOpposite().index() + 1) % 3));
neighb.add(f2.neighbor((e.getOpposite().index() + 2) % 3));
neighb.add(f1.neighbor((e.index() + 1) % 3));
// reset the vertices of the 2 quadrangle faces
f1.setVertex(0, vert.get(0));
f1.setVertex(1, vert.get(1));
f1.setVertex(2, vert.get(2));
f2.setVertex(0, vert.get(0));
f2.setVertex(1, vert.get(2));
f2.setVertex(2, vert.get(3));
// reset the incident faces of the quandrangle vertices
vert.get(0).setFace(f1);
vert.get(1).setFace(f1);
vert.get(2).setFace(f2);
vert.get(3).setFace(f2);
// reset the neighbors of the 2 quadrangle faces
f1.setNeighbor(0, neighb.get(1));
f1.setNeighbor(1, f2);
f1.setNeighbor(2, neighb.get(0));
f2.setNeighbor(0, neighb.get(2));
f2.setNeighbor(1, neighb.get(3));
f2.setNeighbor(2, f1);
// reset the neighbors of the quadrangle neighbors (only modify what needs to be modified)
if (neighb.get(1) != null) neighb.get(1).setNeighbor(neighb.get(1).index(f2), f1);
if (neighb.get(3) != null) neighb.get(3).setNeighbor(neighb.get(3).index(f1), f2);
// reset the marks of the edges of the two faces
for (int i = 0; i < 3; i++) {
f1.unmark(i);
f2.unmark(i);
}
// restore the marks of the quadrangle edges (or rather their inner halfedges)
for (int i = 0; i < 3; i++) {
e = new HalfedgeHandle<X>(f1, i);
if (f1.neighbor(i) != null) e.setMark(e.getOpposite().isMarked());
e = new HalfedgeHandle<X>(f2, i);
if (f2.neighbor(i) != null) e.setMark(e.getOpposite().isMarked());
}
// return the new diagonal edge
return new HalfedgeHandle<X>(f1, 1);
}