/// <summary>
/// Returns all the intersections the line has with this polygon.
/// </summary>
/// <param name="line"></param>
/// <returns></returns>
public PointF2D[] Intersections(LineF2D line)
{
List <PointF2D> points = new List <PointF2D>();
foreach (LineF2D polygon_line in this.LineEnumerator)
{
// calculate the intersection.
PrimitiveF2D primitive = line.Intersection(polygon_line);
// the primitive not null.
if (primitive != null)
{
if (primitive is LineF2D)
{ // primitive is a line; convert.
LineF2D intersect_line =
(primitive as LineF2D);
// we are sure the line is a segment.
// if the line is not a segment this means that the polygon contains an line with infinite length; impossible.
// TODO: how to determine the order?
points.Add(intersect_line.Point1);
points.Add(intersect_line.Point2);
}
else if (primitive is PointF2D)
{ // primitive is a point; convert.
PointF2D point = (primitive as PointF2D);
points.Add(point);
}
}
}
return(points.ToArray());
}
public PointF2D ProjectOn(PointF2D point)
{
if (this.Length == 0.0 && this.IsSegment)
{
return((PointF2D)null);
}
VectorF2D vectorF2D = this.Direction.Rotate90(true);
PointF2D b = new PointF2D((point + vectorF2D).ToArray());
if (point[0] == b[0] && point[1] == b[1])
{
return(b);
}
PrimitiveF2D primitiveF2D = this.Intersection(new LineF2D(point, b, false, false), true);
if (primitiveF2D == null)
{
return((PointF2D)null);
}
if ((object)(primitiveF2D as PointF2D) != null)
{
return(primitiveF2D as PointF2D);
}
throw new InvalidOperationException();
}
/// <summary>
/// Projects a point onto the given line.
///
/// (= intersection of the line with an angle 90° different from this line through the given point)
/// </summary>
/// <param name="point"></param>
/// <returns>The projection point if it occurs inside the segmented line.</returns>
public PointF2D ProjectOn(PointF2D point)
{
if (this.Length == 0 && this.IsSegment)
{ // cannot project on a line of length zero.
return(null);
}
// get the direction.
VectorF2D direction = this.Direction;
// rotate.
VectorF2D rotated = direction.Rotate90(true);
// create second point
PointF2D point2 = new PointF2D((point + rotated).ToArray());
if (point[0] != point2[0] || point[1] != point2[1])
{
// create line.
LineF2D line = new LineF2D(
point,
point2,
false,
false);
// intersect.
PrimitiveF2D primitive =
this.Intersection(line, true);
if (primitive == null)
{
return(null);
}
else if (primitive is PointF2D)
{
return(primitive as PointF2D);
}
else
{
throw new InvalidOperationException();
}
}
else
{
return(point2);
}
}
public PointF2D[] Intersections(LineF2D line)
{
List<PointF2D> pointF2DList = new List<PointF2D>();
foreach (LineF2D line1 in this.LineEnumerator)
{
PrimitiveF2D primitiveF2D = line.Intersection(line1);
if (primitiveF2D != null)
{
if (primitiveF2D is LineF2D)
{
LineF2D lineF2D = primitiveF2D as LineF2D;
pointF2DList.Add(lineF2D.Point1);
pointF2DList.Add(lineF2D.Point2);
}
else if ((object) (primitiveF2D as PointF2D) != null)
{
PointF2D pointF2D = primitiveF2D as PointF2D;
pointF2DList.Add(pointF2D);
}
}
}
return pointF2DList.ToArray();
}