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Voronoi.cs
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Voronoi.cs
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using System;
using System.Collections.Generic;
using System.Drawing;
namespace VoronoiMap {
/// <summary>
/// Adapted from http://philogb.github.io/blog/2010/02/12/voronoi-tessellation/
/// Also uses portions from https://github.com/SirAnthony/cppdelaunay
/// </summary>
public class Voronoi {
private readonly VoronoiGraph _graph;
private readonly SiteList _sites;
private readonly EdgeList _edgeList;
private readonly EventQueue _eventQueue;
private Site _newSite;
private Site _newIntStar;
private bool _edgeFixup;
public int StepNumber { get; private set; }
public Voronoi(IEnumerable<PointF> points, int w = 800, int h = 600, bool debug=false) {
_sites = new SiteList(points);
_sites.LogSites();
_graph = new VoronoiGraph(w, h) {Debug = debug};
_edgeList = new EdgeList(_sites);
_eventQueue = new EventQueue();
_edgeFixup = false;
StepNumber = 0;
}
public VoronoiGraph Initialize() {
_sites.BottomSite = _sites.ExtractMin();
_graph.PlotSite(_sites.BottomSite);
_newSite = _sites.ExtractMin();
if (_newSite.Y > _graph.SweepLine) {
_graph.SweepLine = _newSite.Y;
}
_newIntStar = new Site(float.MaxValue, float.MaxValue);
return _graph;
}
public VoronoiGraph StepVoronoi() {
_graph.ResetNewItems();
if (!_edgeFixup) {
if (!_eventQueue.IsEmpty) {
_newIntStar = _eventQueue.Min();
}
if (_newSite != null && (_eventQueue.IsEmpty || /*Geometry.CompareByYThenX(_newSite, _newIntStar)*/ _newSite.CompareTo(_newIntStar) < 0 )) {
_graph.PlotSite(_newSite);
var lbnd = _edgeList.LeftBound(_newSite);
var rbnd = lbnd.Right;
var bot = _edgeList.RightRegion(lbnd);
var e = Edge.CreateBisectingEdge(bot, _newSite);
_graph.PlotBisector(e);
var bisector = new HalfEdge(e, Side.Left);
EdgeList.Insert(lbnd, bisector);
var p = Site.CreateIntersectingSite(lbnd, bisector);
if (p != null) {
_eventQueue.Delete(lbnd);
if (_graph.Debug) {
Console.WriteLine("Inserting {0}", p);
}
_eventQueue.Insert(lbnd, p, Site.Distance(p, _newSite));
}
lbnd = bisector;
bisector = new HalfEdge(e, Side.Right);
EdgeList.Insert(lbnd, bisector);
p = Site.CreateIntersectingSite(bisector, rbnd);
if (p != null) {
if (_graph.Debug) {
Console.WriteLine("Inserting {0}", p);
}
_eventQueue.Insert(bisector, p, Site.Distance(p, _newSite));
}
_newSite = _sites.ExtractMin();
if (_newSite !=null && _newSite.Y > _graph.SweepLine) {
_graph.SweepLine = _newSite.Y;
} else if (_newSite == null) {
_graph.SweepLine = _graph.Height;
}
} else if (!_eventQueue.IsEmpty) { // intersection is smallest
var lbnd = _eventQueue.ExtractMin();
var llbnd = lbnd.Left;
var rbnd = lbnd.Right;
var rrbnd = rbnd.Right;
var bot = _edgeList.LeftRegion(lbnd);
var top = _edgeList.RightRegion(rbnd);
_graph.PlotTriple(bot, top, _edgeList.RightRegion(lbnd));
var v = lbnd.Vertex;
_graph.PlotVertex(v);
_graph.EndPoint(lbnd.Edge, lbnd.Side, v);
_graph.EndPoint(rbnd.Edge, rbnd.Side, v);
EdgeList.Delete(lbnd);
_eventQueue.Delete(rbnd);
EdgeList.Delete(rbnd);
var pm = Side.Left;
if (bot.Y > top.Y) {
var temp = bot;
bot = top;
top = temp;
pm = Side.Right;
}
var e = Edge.CreateBisectingEdge(bot, top);
_graph.PlotBisector(e);
var bisector = new HalfEdge(e, pm);
EdgeList.Insert(llbnd, bisector);
_graph.EndPoint(e, pm == Side.Left ? Side.Right : Side.Left, v);
var p = Site.CreateIntersectingSite(llbnd, bisector);
if (p != null) {
_eventQueue.Delete(llbnd);
if (_graph.Debug) {
Console.WriteLine("Inserting {0}", p);
}
_eventQueue.Insert(llbnd, p, Site.Distance(p, bot));
}
p = Site.CreateIntersectingSite(bisector, rrbnd);
if (p != null) {
if (_graph.Debug) {
Console.WriteLine("Inserting {0}", p);
}
_eventQueue.Insert(bisector, p, Site.Distance(p, bot));
}
} else {
_edgeFixup = true;
}
StepNumber++;
} else {
var lbnd = _edgeList.LeftEnd.Right;
if (lbnd != _edgeList.RightEnd) {
var e = lbnd.Edge;
_graph.PlotEndpoint(e);
EdgeList.Delete(lbnd);
StepNumber++;
} else {
foreach (var edge in _graph.Edges) {
edge.ClipVertices(new Rectangle(0, 0, _graph.Width, _graph.Height));
}
if (_graph.Debug) {
Console.WriteLine("Done computing graph!");
}
}
}
if (_graph.Debug) {
Console.WriteLine("Step: " + StepNumber);
}
return _graph;
}
}
}