/// <summary>
/// Divide a sub polygon by a line segment.
/// </summary>
/// <param name="lineSegment">the line segment.</param>
/// <param name="poly">the polygon to divide.</param>
/// <returns>one of the sub polygon divided from the polygon.</returns>
internal Polygon2D DividedBy(LineSegment2D lineSegment, Polygon2D poly)
{
if (poly.isDiagonal(lineSegment))
{
int a = poly.HasVertex(lineSegment.FirstPoint);
int b = poly.HasVertex(lineSegment.LastPoint);
if (a > b)
{
int tmp = a;
a = b;
b = tmp;
}
Point2DCollection p2 = new Point2DCollection(b - a + 1);
Point2DCollection p1 = new Point2DCollection(poly.VertexCount - p2.Size + 2);
for (int i = 0; i < poly.VertexCount; i++)
{
if (i <= a || i >= b)
{
p1.Add(poly.GetPoint(i));
}
if (i >= a && i <= b)
{
p2.Add(poly.GetPoint(i));
}
}
if (p1.Count > p2.Count)
{
SubDivision.Add(new Polygon2D(p1));
return(new Polygon2D(p2));
}
else
{
SubDivision.Add(new Polygon2D(p2));
return(new Polygon2D(p1));
}
}
else if (lineSegment.Intersects(poly))
{
Point2DCollection Points = new Point2DCollection(2);
for (int i = 0; i < poly.VertexCount; i++)
{
LineSegment2D border = poly.GetEdge(i);
Point2D p = lineSegment.GetIntersectPoint(border);
if (p.isRegular)
{
Points.DistinctAdd(p);
}
}
Debug.Assert(Points.Count == 2);
if (poly.HasVertex(Points[0]) == Polygon2D.NoSuchPoint)
{
poly.Add(Points[0], poly.OnEdge(Points[0]));
Parent.AddInner(Points[0]);
this.InnerPoints.DistinctAdd(Points[0]);
}
if (poly.HasVertex(Points[1]) == Polygon2D.NoSuchPoint)
{
poly.Add(Points[1], poly.OnEdge(Points[1]));
Parent.AddInner(Points[1]);
this.InnerPoints.DistinctAdd(Points[1]);
}
LineSegment2D line = new LineSegment2D(Points[0], Points[1]);
return(DividedBy(line, poly));
}
else
{
return(poly);
}
}
/// <summary>
/// Add an inner point to the polygon.
/// </summary>
/// <param name="point">the new inner point.</param>
public void AddInnerPoint(Point2D point)
{
Polygon.AddInner(point);
}
