public static SegmentIntersectionType ColinearSegmentIntersection(SegRat2 s, SegRat2 t, ref VecRat2 pointIntersection, ref SegRat2 segmentIntersection)
{
//This check is important for handling degenerate cases like s = [(x,y), (x,y)).
if (s.IsEmpty() || t.IsEmpty())
{
return(SegmentIntersectionType.None);
}
//This check is important because the LineProjectionTransform can only be formed with a non-point segment.
if (s.IsPoint())
{
if (ColinearPointInSegment(s.A, t))
{
pointIntersection = s.A;
return(SegmentIntersectionType.Point);
}
else
{
return(SegmentIntersectionType.None);
}
}
LineProjectionTransform transform = new LineProjectionTransform(s);
SegRat1 proj_s = transform.Project(s);
SegRat1 proj_t = transform.Project(t);
Rational proj_pointIntersection = new Rational();
SegRat1 proj_segmentIntersection = new SegRat1();
SegmentIntersectionType result = SegmentIntersection(
proj_s, proj_t, ref proj_pointIntersection, ref proj_segmentIntersection);
if (result == SegmentIntersectionType.Point)
{
pointIntersection = transform.Unproject(proj_pointIntersection);
}
else if (result == SegmentIntersectionType.Segment)
{
segmentIntersection = transform.Unproject(proj_segmentIntersection);
}
return(result);
}
//If the two segments are disjoint, then None is returned.
//Else, if the two segments are colinear, then either Segment is returned.
//Else, if the two segments are not colinear, Point is returned.
public static SegmentIntersectionType SegmentIntersection(SegRat2 s, SegRat2 t, ref VecRat2 pointIntersection, ref SegRat2 segmentIntersection)
{
//This check is important for handling degenerate cases like s = [(x,y), (x,y)).
if (s.IsEmpty() || t.IsEmpty())
{
return(SegmentIntersectionType.None);
}
//This check is important because the LineProjectionTransform can only be formed with a non-point segment.
if (s.IsPoint())
{
if (PointInSegment(s.A, t))
{
segmentIntersection = s;
return(SegmentIntersectionType.Segment);
}
else
{
return(SegmentIntersectionType.None);
}
}
int turn_s_ta = TurnTest(s, t.A);
int turn_s_tb = TurnTest(s, t.B);
if (turn_s_ta == 0 && turn_s_tb == 0)
{
return(ColinearSegmentIntersection(s, t, ref pointIntersection, ref segmentIntersection));
}
if (s.AClosed)
{
if (t.AClosed && s.A == t.A)
{
pointIntersection = s.A;
return(SegmentIntersectionType.Point);
}
else if (t.BClosed && s.B == t.B)
{
pointIntersection = s.B;
return(SegmentIntersectionType.Point);
}
}
if (s.BClosed)
{
if (t.AClosed && s.B == t.A)
{
pointIntersection = s.B;
return(SegmentIntersectionType.Point);
}
else if (t.BClosed && s.B == t.B)
{
pointIntersection = s.B;
return(SegmentIntersectionType.Point);
}
}
int turn_t_sa = TurnTest(t, s.A);
int turn_t_sb = TurnTest(t, s.B);
int val_s = turn_s_ta * turn_s_tb;
int val_t = turn_t_sa * turn_t_sb;
if (val_s < 0 && val_t < 0)
{
pointIntersection = LineIntersection(s, t);
return(SegmentIntersectionType.Point);
}
else
{
return(SegmentIntersectionType.None);
}
}