/// <summary>
/// Calculates the intersection point of two lines.
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <param name="q1"></param>
/// <param name="q2"></param>
/// <returns></returns>
private Coordinate Intersection(Coordinate p1, Coordinate p2, Coordinate q1, Coordinate q2)
{
Coordinate n1 = new Coordinate(p1);
Coordinate n2 = new Coordinate(p2);
Coordinate n3 = new Coordinate(q1);
Coordinate n4 = new Coordinate(q2);
Coordinate normPt = new Coordinate();
Normalize(n1, n2, n3, n4, normPt);
Coordinate intPt = null;
try
{
intPt = HCoordinate.Intersection(n1, n2, n3, n4);
}
catch (NotRepresentableException e)
{
throw new NotRepresentableException("Coordinate for intersection is not calculable", e);
}
intPt.X += normPt.X;
intPt.Y += normPt.Y;
if (_makePrecise)
{
intPt.MakePrecise();
}
return(intPt);
}
/// <summary>
/// Computes the (approximate) intersection point between two line segments
/// using homogeneous coordinates.
/// </summary>
/// <remarks>Note that this algorithm is
/// not numerically stable; i.e. it can produce intersection points which
/// lie outside the envelope of the line segments themselves. In order
/// to increase the precision of the calculation input points should be normalized
/// before passing them to this routine.
/// </remarks>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <param name="q1"></param>
/// <param name="q2"></param>
/// <returns></returns>
public static Coordinate Intersection(
Coordinate p1, Coordinate p2,
Coordinate q1, Coordinate q2)
{
HCoordinate l1 = new HCoordinate(new HCoordinate(p1), new HCoordinate(p2));
HCoordinate l2 = new HCoordinate(new HCoordinate(q1), new HCoordinate(q2));
HCoordinate intHCoord = new HCoordinate(l1, l2);
Coordinate intPt = intHCoord.GetCoordinate();
return(intPt);
}
/// <summary>
/// Constructs HCoordinate based on p1 and p2.
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
public HCoordinate(HCoordinate p1, HCoordinate p2)
{
_x = p1.Y * p2.W - p2.Y * p1.W;
_y = p2.X * p1.W - p1.X * p2.W;
_w = p1.X * p2.Y - p2.X * p1.Y;
}
