public Edge Locate(Vector2 point, Edge edgeHint)
{
var e = edgeHint;
var t = GeometryHelpers.TriArea(point, e.Dest, e.Orig);
// DPrev------>d----->RPrev
// ^
// |
// e| .P
// |
// ONext<------o<-----RNext
// point is to the right of e
if (t > 0)
{
// Switch search to the left side
t *= -1;
e = e.Sym;
}
while (true)
{
var eo = e.ONext;
var ed = e.DPrev;
// Notice that we're reversing the point order
// this tests that the point is TO THE RIGHT OF the edge
var to = GeometryHelpers.TriArea(point, eo.Dest, eo.Orig);
var td = GeometryHelpers.TriArea(point, ed.Dest, ed.Orig);
// point is below ed (to the right of ed)
if (td > 0)
{
// point is to the right of eo (interior)
// or is e.Orig
if (to > 0 || (to == 0 && t == 0))
{
// DPrev------>d----->RPrev
// ^
// |
// .P e|
// |
// ONext<------o<-----RNext
startingEdge = e;
return(e);
}
else
{
// point is below ed and below eo
// move the search to eo
// DPrev------>d----->RPrev
// ^
// |
// e|
// |
// ONext<------o<-----RNext
// .P
t = to;
e = eo;
}
}
else
{
// point is on or above ed
// point is above eo
if (to > 0)
{
// point is e.Dest
if (td == 0 && t == 0)
{
startingEdge = e;
return(e);
}
else
{
// point is above eo and above ed
// move the search to ed
// .P
// DPrev------>d----->RPrev
// ^
// |
// e|
// |
// ONext<------o<-----RNext
t = td;
e = ed;
}
}
else
{
// point is on or to the left of eo
// point is on e, but the subdivision is to the right
if (t == 0 && !Edge.IsLeftOf(eo.Dest, e))
{
e = e.Sym;
}
// point is on or above ed and on or below eo (what the ...)
// step randomly
else if ((rand.Next() & 1) > 0)
{
t = to;
e = eo;
}
else
{
t = td;
e = ed;
}
}
}
}
}
