public bool Intersects(DoubleLineSegment2 other)
{
double ax = X1, ay = Y1, bx = X2, by = Y2;
double cx = other.X1, cy = other.Y1, dx = other.X2, dy = other.Y2;
return(Intersects(ax, ay, bx, by, cx, cy, dx, dy));
}
public static int Compare(DoubleVector2 p, DoubleLineSegment2 a, DoubleLineSegment2 b)
{
// TODO: Why did I comment this
//#if DEBUG
// if (GeometryOperations.Clockness(p.X, p.Y, a.X1, a.Y1, a.X2, a.Y2) != Clockness.Clockwise) {
// throw new InvalidStateException();
// }
// if (GeometryOperations.Clockness(p.X, p.Y, b.X1, b.Y1, b.X2, b.Y2) != Clockness.Clockwise) {
// throw new InvalidStateException();
// }
//#endif
var clk = GeometryOperations.Clockness(p.X, p.Y, a.X1, a.Y1, b.X1, b.Y1);
if (clk != Clockness.Clockwise)
{
// b before a; b \' a *origin
var res = (int)GeometryOperations.Clockness(b.First, b.Second, a.First);
if (res != 0)
{
return(res);
}
// just need something to resolve ambiguity. b1 b2 a1 is collinear.
// a1 must be within the angle b1 p b2 (see visibility polygon building algorithm)
// so a1 is BETWEEN b1 b2. a2 cannot be collinear with b1 b2 (disallow segments intersecting
// other than at endpoint), but still, a2 is either 'in front of' or 'behind' b.
res = (int)GeometryOperations.Clockness(b.First, b.Second, a.Second);
#if DEBUG
if (res == 0 && a != b)
{
throw new BadInputException();
}
#endif
return(res);
}
else
{
// a before b; a \' b *origin
var res = -(int)GeometryOperations.Clockness(a.First, a.Second, b.First);
if (res != 0)
{
return(res);
}
// just need something to resolve ambiguity. a1 a2 b1 is collinear.
res = -(int)GeometryOperations.Clockness(a.First, a.Second, b.Second);
#if DEBUG
if (res == 0 && a != b)
{
throw new BadInputException();
}
#endif
return(res);
}
}
// assumes p is ccw ordered, edge is counted as interior (neither case)
public static bool SegmentIntersectsNonDegenerateConvexPolygonInterior(DoubleLineSegment2 s, DoubleVector2[] p)
{
#if DEBUG
if (Clockness(p[0], p[1], p[2]) == Clk.Clockwise)
{
throw new BadInputException("p not ccw");
}
if (p.Length < 3)
{
throw new BadInputException("len(p) < 3");
}
#endif
var(x, y) = s;
bool xInterior = true, yInterior = true;
DoubleVector2 a = p[p.Length - 1], b;
int i = 0;
for (; i < p.Length && (xInterior || yInterior); i++, a = b)
{
b = p[i];
var abx = Clockness(a, b, x);
var aby = Clockness(a, b, y);
if (abx == Clk.Clockwise && aby == Clk.Clockwise)
{
return(false);
}
xInterior &= abx != Clk.Clockwise;
yInterior &= aby != Clk.Clockwise;
if (abx == (Clk)(-(int)aby) || abx == Clk.Neither || aby == Clk.Neither)
{
// The below is equivalent to:
// // (a, b) places x, y onto opposite half-planes.
// // Intersect if (x, y) places a, b onto opposite half-planes.
// var xya = Clockness(x, y, a);
// var xyb = Clockness(x, y, b);
// if (xya != xyb || xya == Clk.Neither || xyb == Clk.Neither) return true;
if (DoubleLineSegment2.Intersects(a.X, a.Y, b.X, b.Y, x.X, x.Y, y.X, y.Y))
{
return(true);
}
}
}
for (; i < p.Length; i++, a = b)
{
b = p[i];
if (DoubleLineSegment2.Intersects(a.X, a.Y, b.X, b.Y, x.X, x.Y, y.X, y.Y))
{
return(true);
}
}
return(xInterior && yInterior);
}
public static bool SegmentIntersectsConvexPolygonInterior(DoubleLineSegment2 s, DoubleVector2[] p)
{
if (p.Length == 1)
{
return(false);
}
else if (p.Length == 2)
{
return(s.Intersects(new DoubleLineSegment2(p[0], p[1])));
}
else
{
return(SegmentIntersectsNonDegenerateConvexPolygonInterior(s, p));
}
}
public static DoubleVector2 FindNearestPoint(DoubleLineSegment2 segment, DoubleVector2 query)
{
return(FindNearestPoint(segment.First, segment.Second, query));
}
// NOTE: Assumes lines are valid (two distinct endpoints) NOT line-OVERLAPPING
// that is, lines should not have more than 1 point of intersection.
// if lines DO have more than 1 point of intersection, this returns no intersection found.
public static bool TryFindNonoverlappingLineLineIntersectionT(ref DoubleLineSegment2 a, ref DoubleLineSegment2 b, out double tForA)
{
return(TryFindNonoverlappingLineLineIntersectionT(a.First, a.Second, b.First, b.Second, out tForA));
}
// Equality by endpoints, not line geometry
public bool Equals(DoubleLineSegment2 other)
{
return(First == other.First && Second == other.Second);
}