Edge* Subdivision::Locate(const Point2d& x)
// Returns an edge e, s.t. either x is on e, or e is an edge of
// a triangle containing x. The search starts from startingEdge
// and proceeds in the general direction of x. Based on the
// pseudocode in Guibas and Stolfi (1985) p.121.
{
Edge* e = startingEdge;
while (TRUE) {
if (x == e->Org2d() || x == e->Dest2d())
return e;
else if (RightOf(x, e))
e = e->Sym();
else if (!RightOf(x, e->Onext()))
e = e->Onext();
else if (!RightOf(x, e->Dprev()))
e = e->Dprev();
else
return e;
}
}
Edge *Subdivision::locate(const Vec2& x, Edge *start)
{
Edge *e = start;
double t = triArea(x, e->Dest(), e->Org());
if (t>0) { // x is to the right of edge e
t = -t;
e = e->Sym();
}
while (true)
{
Edge *eo = e->Onext();
Edge *ed = e->Dprev();
double to = triArea(x, eo->Dest(), eo->Org());
double td = triArea(x, ed->Dest(), ed->Org());
if (td>0) // x is below ed
if (to>0 || to==0 && t==0) {// x is interior, or origin endpoint
startingEdge = e;
return e;
}
else { // x is below ed, below eo
t = to;
e = eo;
}
else // x is on or above ed
if (to>0) // x is above eo
if (td==0 && t==0) { // x is destination endpoint
startingEdge = e;
return e;
}
else { // x is on or above ed and above eo
t = td;
e = ed;
}
else // x is on or below eo
if (t==0 && !leftOf(eo->Dest(), e))
// x on e but subdiv. is to right
e = e->Sym();
else if (rand()&1) { // x is on or above ed and
t = to; // on or below eo; step randomly
e = eo;
}
else {
t = td;
e = ed;
}
}
}
int main() {
using cgl::Point2d;
using cgl::Edge;
using cgl::make_edge;
// Point2d *a = new Point2d(0.0, 0.0); // 0
// Point2d *b = new Point2d(1.0, 0.0); // 1
// Point2d *c = new Point2d(1.0, 1.0); // 2
// Point2d *d = new Point2d(0.0, 1.0); // 3
Edge *ea = make_edge(0, 1);
Edge *eb = make_edge(ea->Dest(), 2);
Edge *ec = make_edge(eb->Dest(), 3);
Edge *ed = make_edge(ec->Dest(), 0);
Edge *ee = make_edge(eb->Dest(), ea->Org());
// Connect eb to ea->Dest()
splice(ea->Sym(), eb);
// Connect ec to eb->Dest()
splice(eb->Sym(), ec);
// Connect ed to ec->Sym() and ea
splice(ec->Sym(), ed);
splice(ed->Sym(), ea);
// Connect ee to ec and ea -- this is equivalent to Delaunay::connect
splice(ee, eb->Lnext());
splice(ee->Sym(), ea);
// Traverse the convex hull
if (ea->Dnext() != eb->Sym()) {
std::cerr << "Error: ea->Dnext() != eb->Sym()" << std::endl;
return 1;
}
if (eb->Dnext() != ec->Sym()) {
std::cerr << "Error: eb->Dnext() != ec->Sym()" << std::endl;
return 1;
}
if (ec->Dnext() != ed->Sym()) {
std::cerr << "Error: ec->Dnext() != ed->Sym()" << std::endl;
return 1;
}
if (ed->Dprev() != ee) {
std::cerr << "Error: ed->Dprev() != ee" << std::endl;
return 1;
}
// Cross linkage -- test algebra
// Rot / invRot
if (ee->Rot()->Org() != ed->invRot()->Org()) {
std::cerr << "Error: ee->Rot()->Org() != ed->invRot()->Org()" <<
std::endl;
return 1;
}
// Sym
if (ee->Sym()->Org() != 0) {
std::cerr << "Error: ee->Sym()->Org() != a" << std::endl;
return 1;
}
// Onext
if (ee->Onext() != eb->Sym()) {
std::cerr << "Error: ee->Onext() != eb->Sym()" << std::endl;
return 1;
}
// Oprev
if (ee->Oprev() != ec) {
std::cerr << "Error: ee->Oprev() != ec" << std::endl;
return 1;
}
// Dnext
if (ee->Dnext() != ed) {
std::cerr << "Error: ee->Dnext() != ed" << std::endl;
return 1;
}
// Dprev
if (ee->Dprev() != ea->Sym()) {
std::cerr << "Error: ee->Dprev() != ea->Sym()" << std::endl;
return 1;
}
// Lnext
if (ee->Lnext() != ea) {
std::cerr << "Error: ee->Lnext() != ea" << std::endl;
return 1;
}
// Lprev
if (ee->Lprev() != eb) {
std::cerr << "Error: ee->Lprev() != eb" << std::endl;
return 1;
}
// Rnext
if (ee->Rnext() != ec->Sym()) {
std::cerr << "Error: ee->Rnext() != ec->Sym()" << std::endl;
return 1;
}
// Rprev
if (ee->Rprev() != ed->Sym()) {
std::cerr << "Error: ee->Rprev() != ed->Sym()" << std::endl;
return 1;
}
// Org / Dest
if (ed->Org() != 3) {
std::cerr << "Error: ed->Org() != d" << std::endl;
return 1;
}
if (ed->Dest() != 0) {
std::cerr << "Error: ed->Dest() != a" << std::endl;
return 1;
}
if (ee->Org() != 2) {
std::cerr << "Error: ee->Org() != c" << std::endl;
return 1;
}
if (ee->Dest() != 0) {
std::cerr << "Error: ee->Dest() != a" << std::endl;
return 1;
}
// Let the system clean up the memory
return 0;
}