public static Face makeCcw(Face f, Edge e, Vertex p) {
int i;
Face invisibleFace;
if (e.getAdjface(1) == null) {
invisibleFace = e.getAdjface(0);
} else {
if (!e.getAdjface(0).visible) {
invisibleFace = e.getAdjface(0);
} else {
invisibleFace = e.getAdjface(1);
}
}
for (i = 0; invisibleFace.getVertex(i) != e.getEndpt(1); i++) {}
if (invisibleFace.getVertex((i + 1) % 3) != e.getEndpt(0)) {
f.setVertex(0, e.getEndpt(1));
f.setVertex(1, e.getEndpt(0));
} else {
f.setVertex(0, e.getEndpt(0));
f.setVertex(1, e.getEndpt(1));
swap(f.getEdge(1), f.getEdge(2));
}
f.setVertex(2, p);
return f;
}
public static void buildTetrahedron() {
QueueElement<Vertex> v0;
QueueElement<Vertex> v3;
int volume;
// find 3 noncollinear points
v0 = ConvexHull.vertices.getFirst();
while (collinear(v0.getElem(), v0.getNext().getElem(), v0.getNext().getNext().getElem())) {
v0 = v0.getNext();
if (v0.getNext() == ConvexHull.vertices.getFirst()) {
System.err.println("All points are collinear");
System.exit(0);
}
}
// mark vertices as processed
v0.getElem().setMark(true);
v0.getNext().getElem().setMark(true);
v0.getNext().getNext().getElem().setMark(true);
Edge e0 = Edge.makeEdge(v0.getElem(), v0.getNext().getElem());
Edge e1 = Edge.makeEdge(v0.getNext().getElem(), v0.getNext().getNext().getElem());
Edge e2 = Edge.makeEdge(v0.getNext().getNext().getElem(), v0.getElem());
Face f = Face.makeFace(e0, e1, e2);
f.setVertices(v0.getElem(), v0.getNext().getElem(), v0.getNext().getNext().getElem());
e0.setAdjface(0, f);
e1.setAdjface(0, f);
e1.setAdjface(0, f);
// try to find another noncollinear vertex
v3 = v0.getNext().getNext().getNext();
volume = volume(f, v3.getElem());
while (volume == 0) {
v3 = v3.getNext();
if (v3 == ConvexHull.vertices.getFirst()) {
System.err.println("All points are coplanar");
System.exit(0);
}
volume = volume(f, v3.getElem());
}
v3.getElem().setMark(true);
// store vertices in ccw order
if (volume < 0) {
swap(f.getVertex(1), f.getVertex(2));
swap(f.getEdge(1), f.getEdge(2));
}
e0.setAdjface(1, makeStructs(e0, v3.getElem()));
e1.setAdjface(1, makeStructs(e1, v3.getElem()));
e2.setAdjface(1, makeStructs(e2, v3.getElem()));
Cleaning.cleanUp();
}
private static int volume(Face f, Vertex p) {
double ax = f.getVertex(0).getCoordinate(0) - p.getCoordinate(0);
double ay = f.getVertex(0).getCoordinate(1) - p.getCoordinate(1);
double az = f.getVertex(0).getCoordinate(2) - p.getCoordinate(2);
double bx = f.getVertex(1).getCoordinate(0) - p.getCoordinate(0);
double by = f.getVertex(1).getCoordinate(1) - p.getCoordinate(1);
double bz = f.getVertex(1).getCoordinate(2) - p.getCoordinate(2);
double cx = f.getVertex(2).getCoordinate(0) - p.getCoordinate(0);
double cy = f.getVertex(2).getCoordinate(1) - p.getCoordinate(1);
double cz = f.getVertex(2).getCoordinate(2) - p.getCoordinate(2);
double volume = ax * (by * cz - bz * cy) + ay * (bz * cx - bx * cz) + az * (bx * cy - by * cx);
if (volume > 0.5) {
return 1;
} else if (volume < -0.5) {
return -1;
} else {
return 0;
}
}
