private void clipBtn_Click(object sender, RoutedEventArgs e)
{
CGPolygon polygon = new CGPolygon(PolygonPoints);
List <CGLine> segments = new List <CGLine>();
foreach (var l in this.Lines)
{
Point a = new Point(l.X1, l.Y1);
Point b = new Point(l.X2, l.Y2);
CGLine S = new CGLine(a, b);
segments.Add(S);
}
List <Point> pList = new List <Point>();
var x = polygon.Clip(segments);
foreach (var item in x)
{
Line ln = new Line();
ln.X1 = item.A.X;
ln.Y1 = item.A.Y;
ln.X2 = item.B.X;
ln.Y2 = item.B.Y;
ln.Stroke = Brushes.Pink;
ln.StrokeThickness = 2;
mainContainer.Children.Add(ln);
}
}
public double IntersectionParameter(CGLine that)
{
var edge = that;
var segmentToEdge = edge.A.Substract(this.A);
var segmentDir = this.Direction;
var edgeDir = edge.Direction;
var t = edgeDir.CrossProduct(segmentToEdge) / edgeDir.CrossProduct(segmentDir);
if (double.IsNaN(t))
{
t = 0;
}
return(t);
}
private CGLine ClipLine(CGLine line)
{
double tE = 0, tL = 1;
var dir = line.Direction;
Point nL;
bool PE = false;
foreach (var edge in this.Edges)
{
nL = edge.Normal;
var t = line.IntersectionParameter(edge);
double slope = nL.DotProduct(dir);
PE = (slope < 0 ? true : false);
//potentionally entering
if (PE)
{
//Choose for parameter tE the largest t ≤ 1 from the PE set
if (t > tE)
{
tE = t;
}
//potentionally leaving
}
else
{
//Choose for parameter tL the smallest t ≥ 0 from the PL set
if (t < tL)
{
tL = t;
}
}
}
//Line is discarded if tE > tL
if (tE > tL)
{
return(null);
}
//Clipped line is defined by [tE , tL]
return(line.Morph(tE, tL));
}
public List <CGLine> Clip(List <CGLine> lines)
{
if (!this.IsConvex())
{
this.Points.Reverse();
}
var clippedLines = new List <CGLine>();
foreach (var line in lines)
{
CGLine clippedSegment = this.ClipLine(line);
if (clippedSegment != null)
{
clippedLines.Add(clippedSegment);
}
}
return(clippedLines);
}