/// <summary>
/// Computes the (approximate) intersection point between two line segments
/// using homogeneous coordinates.
/// 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.
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <param name="q1"></param>
/// <param name="q2"></param>
/// <returns></returns>
public static Coordinate OldIntersection(Coordinate p1, Coordinate p2, Coordinate q1, Coordinate q2)
{
var l1 = new HCoordinate(new HCoordinate(p1), new HCoordinate(p2));
var l2 = new HCoordinate(new HCoordinate(q1), new HCoordinate(q2));
var intHCoord = new HCoordinate(l1, l2);
var intPt = intHCoord.Coordinate;
return(intPt);
}
/// <summary>
/// Computes a segment intersection using homogeneous coordinates.
/// Round-off error can cause the raw computation to fail,
/// (usually due to the segments being approximately parallel).
/// If this happens, a reasonable approximation is computed instead.
/// </summary>
private static Coordinate SafeHCoordinateIntersection(Coordinate p1, Coordinate p2, Coordinate q1, Coordinate q2)
{
Coordinate intPt;
try
{
intPt = HCoordinate.Intersection(p1, p2, q1, q2);
}
catch (NotRepresentableException e)
{
intPt = CentralEndpointIntersector.GetIntersection(p1, p2, q1, q2);
}
return(intPt);
}
/// <summary>
/// Computes a segment intersection using homogeneous coordinates.
/// Round-off error can cause the raw computation to fail,
/// (usually due to the segments being approximately parallel).
/// If this happens, a reasonable approximation is computed instead.
/// </summary>
private static Coordinate SafeHCoordinateIntersection(Coordinate p1, Coordinate p2, Coordinate q1, Coordinate q2)
{
Coordinate intPt;
try
{
intPt = HCoordinate.Intersection(p1, p2, q1, q2);
}
catch (NotRepresentableException e)
{
// compute an approximate result
// intPt = CentralEndpointIntersector.GetIntersection(p1, p2, q1, q2);
intPt = NearestEndpoint(p1, p2, q1, q2);
}
return(intPt);
}
/// <summary>
///
/// </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;
}
