/// <summary>
/// Compute the intersection of a point p and the line p1-p2.
/// </summary>
/// <param name="p">The test point.</param>
/// <param name="p1">The starting coordinate of the line.</param>
/// <param name="p2">The ending coordinate of the line.</param>
/// <remarks>
/// This function computes the boolean value of the HasIntersection test.
/// The actual value of the intersection (if there is one)
/// is equal to the value of p.
/// </remarks>
public override void ComputeIntersection(Coordinate p, Coordinate p1, Coordinate p2)
{
if (p1 == null)
{
throw new ArgumentNullException("p1");
}
if (p2 == null)
{
throw new ArgumentNullException("p2");
}
if (p == null)
{
throw new ArgumentNullException("p");
}
m_bIsProper = false;
// do between check first, since it is faster than the orientation test
if (Envelope.Intersects(p1, p2, p))
{
if ((RobustCGAlgorithms.OrientationIndex(p1, p2, p) == 0) &&
(RobustCGAlgorithms.OrientationIndex(p2, p1, p) == 0))
{
m_bIsProper = true;
if (p.Equals(p1) || p.Equals(p2))
{
m_bIsProper = false;
}
result = (int)IntersectState.DoIntersect;
return;
}
}
result = (int)IntersectState.DonotIntersect;
}
/// <summary>
/// Computes the intersection of the lines p1-p2 and q1-q2.
/// </summary>
/// <param name="p1">The starting coordinate of first line.</param>
/// <param name="p2">The ending coordinate of first line.</param>
/// <param name="q1">The starting coordinate of seocnd line.</param>
/// <param name="q2">The ending coordinate of second line.</param>
/// <returns>
/// A integer, which is one of the <see cref="IntersectState"/> values,
/// specifying the intersection state of the lines.
/// </returns>
protected override int ComputeIntersect(Coordinate p1, Coordinate p2,
Coordinate q1, Coordinate q2)
{
if (p1 == null)
{
throw new ArgumentNullException("p1");
}
if (p2 == null)
{
throw new ArgumentNullException("p2");
}
if (q1 == null)
{
throw new ArgumentNullException("q1");
}
if (q2 == null)
{
throw new ArgumentNullException("q2");
}
m_bIsProper = false;
// first try a fast test to see if the envelopes of the lines intersect
if (!Envelope.Intersects(p1, p2, q1, q2))
{
return((int)IntersectState.DonotIntersect);
}
// for each endpoint, compute which side of the other segment it lies
// if both endpoints lie on the same side of the other segment,
// the segments do not intersect
int Pq1 = RobustCGAlgorithms.OrientationIndex(p1, p2, q1);
int Pq2 = RobustCGAlgorithms.OrientationIndex(p1, p2, q2);
if ((Pq1 > 0 && Pq2 > 0) || (Pq1 < 0 && Pq2 < 0))
{
return((int)IntersectState.DonotIntersect);
}
int Qp1 = RobustCGAlgorithms.OrientationIndex(q1, q2, p1);
int Qp2 = RobustCGAlgorithms.OrientationIndex(q1, q2, p2);
if ((Qp1 > 0 && Qp2 > 0) || (Qp1 < 0 && Qp2 < 0))
{
return((int)IntersectState.DonotIntersect);
}
bool collinear = Pq1 == 0 && Pq2 == 0 && Qp1 == 0 && Qp2 == 0;
if (collinear)
{
return(ComputeCollinearIntersection(p1, p2, q1, q2));
}
// Check if the intersection is an endpoint. If it is, copy the endpoint as
// the intersection point. Copying the point rather than computing it
// ensures the point has the exact value, which is important for
// robustness. It is sufficient to simply check for an endpoint which is on
// the other line, since at this point we know that the inputLines must
// intersect.
if (Pq1 == 0 || Pq2 == 0 || Qp1 == 0 || Qp2 == 0)
{
m_bIsProper = false;
if (Pq1 == 0)
{
intPt[0] = new Coordinate(q1);
}
if (Pq2 == 0)
{
intPt[0] = new Coordinate(q2);
}
if (Qp1 == 0)
{
intPt[0] = new Coordinate(p1);
}
if (Qp2 == 0)
{
intPt[0] = new Coordinate(p2);
}
}
else
{
m_bIsProper = true;
intPt[0] = Intersection(p1, p2, q1, q2);
}
return((int)IntersectState.DoIntersect);
}