public void Compute(HashSet<Point> points, int width, int height)
{
_root = null;
_width = width;
_height = height;
if (points.Count < 2)
{
return;
}
Edges = new List<Edge>();
Cells = new List<Cell>();
_queue = new Queue();
foreach (Point point in points)
{
var @event = new Event(point, true);
var cell = new Cell(point);
point.Cell = cell;
_queue.Enqueue(@event);
Cells.Add(cell);
}
while (!_queue.IsEmpty())
{
Event @event = _queue.Dequeue();
_ly = @event.Point.Y;
if (@event.IsParabola)
{
InsertParabola(@event.Point);
}
else
{
RemoveParabola(@event);
}
_lasty = @event.Point.Y;
}
FinishEdge(_root);
for (var i = 0; i < Edges.Count; i++)
{
if (Edges[i].Neighbour != null)
{
Edges[i].Start = Edges[i].Neighbour.End;
}
}
}
private void CheckCircle(Parabola b)
{
Parabola lp = GetLeftParent(b);
Parabola rp = GetRightParent(b);
Parabola a = GetLeftChild(lp);
Parabola c = GetRightChild(rp);
if (a == null || c == null || Equals(a.Site, c.Site)) return;
Point s = GetEdgeIntersection(lp.Edge, rp.Edge);
if (s == null) return;
double d = Distance(a.Site, s);
if (s.Y - d >= _ly) return;
var e = new Event(new Point(s.X, s.Y - d), false);
b.CircleEvent = e;
e.Arch = b;
_queue.Enqueue(e);
}
private void InsertParabola(Point p)
{
if (_root == null)
{
_root = new Parabola(p);
_fp = p;
return;
}
if (_root.IsLeaf && _root.Site.Y - p.Y < 0.01)
{
_root.IsLeaf = false;
_root.Left = new Parabola(_fp);
_root.Right = new Parabola(p);
var s = new Point((p.X + _fp.X)/2, _height);
if (p.X > _fp.X)
{
_root.Edge = new Edge(s, _fp, p);
}
else
{
_root.Edge = new Edge(s, p, _fp);
}
Edges.Add(_root.Edge);
return;
}
Parabola par = GetParabolaByX(p.X);
if (par.CircleEvent != null)
{
_queue.Remove(par.CircleEvent);
par.CircleEvent = null;
}
var start = new Point(p.X, GetY(par.Site, p.X));
var el = new Edge(start, par.Site, p);
var er = new Edge(start, p, par.Site);
el.Neighbour = er;
Edges.Add(el);
par.Edge = er;
par.IsLeaf = false;
var p0 = new Parabola(par.Site);
var p1 = new Parabola(p);
var p2 = new Parabola(par.Site);
par.Right = p2;
par.Left = new Parabola();
par.Left.Edge = el;
par.Left.Left = p0;
par.Left.Right = p1;
CheckCircle(p0);
CheckCircle(p2);
}
private double GetXOfEdge(Parabola par, double y)
{
Parabola left = GetLeftChild(par);
Parabola right = GetRightChild(par);
Point p = left.Site;
Point r = right.Site;
double dp = 2*(p.Y - y);
double a1 = 1/dp;
double b1 = -2*p.X/dp;
double c1 = y + dp*0.25 + p.X*p.X/dp;
dp = 2*(r.Y - y);
double a2 = 1/dp;
double b2 = -2*r.X/dp;
double c2 = y + dp*0.25 + r.X*r.X/dp;
double a = a1 - a2;
double b = b1 - b2;
double c = c1 - c2;
double disc = b*b - 4*a*c;
double x1 = (-b + Math.Sqrt(disc))/(2*a);
double x2 = (-b - Math.Sqrt(disc))/(2*a);
double ry;
if (p.Y < r.Y) ry = Math.Max(x1, x2);
else ry = Math.Min(x1, x2);
return ry;
}
private Parabola GetRightParent(Parabola n)
{
Parabola par = n.Parent;
Parabola pLast = n;
while (par.Right == pLast)
{
if (par.Parent == null) return null;
pLast = par;
par = par.Parent;
}
return par;
}
private Parabola GetRightChild(Parabola n)
{
if (n == null) return null;
Parabola par = n.Right;
while (!par.IsLeaf) par = par.Left;
return par;
}
private void FinishEdge(Parabola n)
{
double mx;
if (n.Edge.Direction.X > 0.0f)
{
mx = Math.Max(_width, n.Edge.Start.X + 10);
}
else
{
mx = Math.Min(0.0f, n.Edge.Start.X - 10);
}
n.Edge.End = new Point(mx, n.Edge.F * mx + n.Edge.G);
if (!n.Left.IsLeaf) this.FinishEdge(n.Left);
if (!n.Right.IsLeaf) this.FinishEdge(n.Right);
}
