/// <summary>
/// Returns the intersection of the specified segment with this bounding box. If there is no intersection,
/// then this returns null. If the intersection is a corner, then the LineSegment will be degenerate,
/// that is both the coordinates will be the same. Otherwise, the segment will be returned so that the
/// direction is the same as the original segment.
/// </summary>
/// <param name="self">The IEnvelope to use with this method</param>
/// <param name="segment">The LineSegment to intersect.</param>
/// <returns>An ILineSegment that is cropped to fit within the bounding box.</returns>
public static ILineSegment Intersection(this IEnvelope self, ILineSegment segment)
{
if (self == null)
{
return(null);
}
if (self.IsNull)
{
return(null);
}
if (segment == null)
{
return(null);
}
// If the line segment is completely contained by this envelope, simply return the original.
if (self.Contains(segment.P0) && self.Contains(segment.P1))
{
return(segment);
}
int count = 0;
Coordinate[] borderPoints = new Coordinate[2];
ILineSegment[] border = self.BorderSegments();
for (int i = 0; i < 4; i++)
{
borderPoints[count] = border[i].Intersection(segment);
if (borderPoints[count] != null)
{
count++;
if (count > 1)
{
break;
}
}
}
// If there are two intersections, the line crosses this envelope
if (count == 2)
{
Vector v = new Vector(segment.P0, segment.P1);
Vector t = new Vector(borderPoints[0], borderPoints[1]);
return(t.Dot(v) < 0 ? new LineSegment(borderPoints[1], borderPoints[0]) : new LineSegment(borderPoints[0], borderPoints[1]));
}
// if there is only one intersection, we probably have one point contained and one point not-contained
if (count == 1)
{
if (self.Contains(segment.P0))
{
// P1 got cropped, so make a line from p0 to the cropped point
return(new LineSegment(segment.P0, borderPoints[0]));
}
return(self.Contains(segment.P1) ? new LineSegment(borderPoints[0], segment.P1) : new LineSegment(borderPoints[0], borderPoints[0]));
}
return(null);
}