/// <summary>
/// Checks whether this link object intersects another one.
/// </summary>
/// <param name="other">The other link to check.</param>
/// <returns>
/// True if there is an intersection. False if:
///
/// 1. The other link is THIS link.
/// 2. This link is the end of a link.
/// 3. This link has no link.
/// 4. The other link is the end of any link.
/// 5. The other link is not linked.
/// 6. There is no intersection.
/// </returns>
internal bool IsIntersected(PolygonLink other)
{
// The other object can't be THIS object.
if (Object.ReferenceEquals(other, this))
{
return(false);
}
// The other can't be linked to this.
if (Object.ReferenceEquals(other, m_Link))
{
return(false);
}
// Both objects must be linked.
if (m_Link == null || other.Link == null)
{
return(false);
}
// It must be the START of both links.
if (m_IsEnd || other.IsEnd)
{
return(false);
}
// Get the position of this link.
double xk = m_Point.X;
double yk = m_Point.Y;
double xl = m_Link.Point.X;
double yl = m_Link.Point.Y;
// Get the position of the other link.
double xm = other.Point.X;
double ym = other.Point.Y;
double xn = other.Link.Point.X;
double yn = other.Link.Point.Y;
// Return if there is any intersection along the length of the test segments.
double xi, yi;
return(Geom.CalcIntersect(xk, yk, xl, yl,
xm, ym, xn, yn,
out xi, out yi, true) != 0);
}
/// <summary>
/// Intersects this multi-segment with itself. Only SIMPLE intersections will be
/// found. There are no special checks for multi-segments that graze themselves.
/// </summary>
/// <param name="xsect">The intersection results.</param>
/// <returns>The number of self-intersections found.</returns>
uint SelfIntersect(IntersectionResult xsect)
{
uint nx = 0;
// Get an array of cumulative distances for each segment.
IPointGeometry[] data = this.Data;
double[] cumdist = GetCumDist(data);
// Note start of initial segment (treat as the end of some imaginary line prior to the start).
double xs;
double ys;
double xe = data[0].X;
double ye = data[0].Y;
// How many line segments have we got?
int nseg = data.Length - 1;
// Loop through each segment, intersecting it with all subsequent
// segments, except for the one that immediately follows.
for (int iseg = 1; iseg <= (nseg - 2); iseg++)
{
// The start of this segment is the end of the previous one.
xs = xe;
ys = ye;
// Get the position of the end of the test segment
xe = data[iseg].X;
ye = data[iseg].Y;
// Compare against subsequent segments (except the next one)
for (int jseg = iseg + 2; jseg <= nseg; jseg++)
{
IPointGeometry start = data[jseg - 1];
IPointGeometry end = data[jseg];
double xi, yi;
if (Geom.CalcIntersect(start.X, start.Y, end.X, end.Y, xs, ys, xe, ye, out xi, out yi, true) != 0)
{
// Define distance to the intersection on the i-segment
double dx = xi - xs;
double dy = yi - ys;
double ilen = cumdist[iseg - 1] + Math.Sqrt(dx * dx + dy * dy);
// Likewise for the j-segment
dx = xi - start.X;
dy = yi - start.Y;
double jlen = cumdist[jseg - 1] + Math.Sqrt(dx * dx + dy * dy);
// Append TWO intersections.
xsect.Append(xi, yi, ilen);
xsect.Append(xi, yi, jlen);
nx += 2;
}
}
}
// Sort the intersections (DON'T set new sort values).
xsect.Sort(false);
// Return the number of intersections
return(nx);
}