/// <summary>
/// Test the intersection beween 2 lines
/// </summary>
/// <param name="L1">Line 1</param>
/// <param name="L2">Line 2</param>
/// <returns></returns>
public static bool intersect(Line3D L1, Line3D L2)
{
Point3D p = new Point3D();
return(Line3D.intersect(L1, L2, out p));
}
/// <summary>
/// Testing whether 2 line segments intersect
/// </summary>
/// <param name="L1">Line 1</param>
/// <param name="L2">Line 2</param>
/// <param name="intersectionPoint">Intersection point</param>
/// <param name="mode">enumeration that identifies how the two lines intersect</param>
/// <returns></returns>
public static bool intersect(LineSegment3D L1, LineSegment3D L2, out Point3D intersectionPoint, out LineSegmentIntersectEnum mode)
{
mode = LineSegmentIntersectEnum.Undefined;
Point3D ip = new Point3D();
intersectionPoint = ip;
if (Line3D.parallel(L1.baseLine, L2.baseLine))
{
return(false); // Lines are parallel, no intersection
}
// With segments AB and CD, we get Pab = (1-s)A + sB, and Qab = (1-t)C + D
// For intersection Pab = Qcd and therefore (1-s)A + sB = (1-t)C + tD. We get s(B-A) - t(D-C) = C-A for some s,t
// using matrix operation we can get s and t using X and Y, and also using X and Z. If they intersect s and t have to be equal for both
double a = L1.endPoint.X - L1.startPoint.X;
double b = L2.startPoint.X - L2.endPoint.X;
double c = L1.endPoint.Y - L1.startPoint.Y;
double d = L2.startPoint.Y - L2.endPoint.Y;
double e = L1.endPoint.Z - L1.startPoint.Z;
double f = L2.startPoint.Z - L2.endPoint.Z;
double g = L2.startPoint.X - L1.startPoint.X;
double h = L2.startPoint.Y - L1.startPoint.Y;
double i = L2.startPoint.Z - L1.startPoint.Z;
// Work on special case when the lines are 2D
if ((MathUtils.equalTol(a, 0.0) && MathUtils.equalTol(b, 0.0) && MathUtils.equalTol(g, 0.0)) ||
(MathUtils.equalTol(e, 0.0) && MathUtils.equalTol(f, 0.0) && MathUtils.equalTol(i, 0.0)) ||
(MathUtils.equalTol(c, 0.0) && MathUtils.equalTol(d, 0.0) && MathUtils.equalTol(h, 0.0)))
{
double s = -1.0;
double t = -1.0;
// 2D line segments on Y-Z plane (X = 0)
if (MathUtils.equalTol(a, 0.0) && MathUtils.equalTol(b, 0.0) && MathUtils.equalTol(g, 0.0))
{
s = (d * i - h * f) / (d * e - c * f);
t = (e * h - i * c) / (d * e - c * f);
}
// 2D line segments on X-Y plane (Z = 0)
else if (MathUtils.equalTol(e, 0.0) && MathUtils.equalTol(f, 0.0) && MathUtils.equalTol(i, 0.0))
{
s = (b * h - g * d) / (b * c - a * d);
t = (g * c - h * a) / (b * c - a * d);
}
// 2D line segment on X-Z plane (Y = 0)
else if (MathUtils.equalTol(c, 0.0) && MathUtils.equalTol(d, 0.0) && MathUtils.equalTol(h, 0.0))
{
s = (b * i - g * f) / (b * e - a * f);
t = (g * e - i * a) / (b * e - a * f);
}
// calculate intersection point
ip.X = (1 - s) * L1.startPoint.X + s * L1.endPoint.X;
ip.Y = (1 - s) * L1.startPoint.Y + s * L1.endPoint.Y;
ip.Z = (1 - s) * L1.startPoint.Z + s * L1.endPoint.Z;
intersectionPoint = ip;
if ((0 <= s && s <= 1) && (0 <= t && t <= 1))
{
// If the segments intersect s and t have to be between 0 and 1
mode = LineSegmentIntersectEnum.IntersectedWithinSegments;
return(true);
}
else
{
// Lines intersect but intersection occurs outside of the segments
mode = LineSegmentIntersectEnum.IntersectedOutsideSegments;
return(false);
}
}
// Line segments are real 3D lines
{
// on X-Y
double s1 = (b * h - g * d) / (b * c - a * d);
double t1 = (g * c - h * a) / (b * c - a * d);
// on X-Z
double s2 = (b * i - g * f) / (b * e - a * f);
double t2 = (g * e - i * a) / (b * e - a * f);
// on Y-Z
double s3 = (d * i - h * f) / (d * e - c * f);
double t3 = (e * h - i * c) / (d * e - c * f);
// When the result of calculation gives infinity or NaN, the line is somewhat aligned, so it can hav any value. Set it here to be the same with one other
if (double.IsInfinity(s1) || double.IsNaN(s1))
{
if (double.IsInfinity(s2) || double.IsNaN(s2))
{
if (double.IsInfinity(s3) || double.IsNaN(s3))
{
s1 = 0.0;
}
else
{
s1 = s3;
}
}
else
{
s1 = s2;
}
}
if (double.IsInfinity(s2) || double.IsNaN(s2))
{
if (double.IsInfinity(s1) || double.IsNaN(s1))
{
if (double.IsInfinity(s3) || double.IsNaN(s3))
{
s2 = 0.0;
}
else
{
s2 = s3;
}
}
else
{
s2 = s1;
}
}
if (double.IsInfinity(s3) || double.IsNaN(s3))
{
if (double.IsInfinity(s1) || double.IsNaN(s1))
{
if (double.IsInfinity(s2) || double.IsNaN(s2))
{
s3 = 0.0;
}
else
{
s3 = s2;
}
}
else
{
s3 = s1;
}
}
// When the result of calculation gives infinity or NaN, the line is somewhat aligned, so it can hav any value. Set it here to be the same with one other
if (double.IsInfinity(t1) || double.IsNaN(t1))
{
if (double.IsInfinity(t2) || double.IsNaN(t2))
{
if (double.IsInfinity(t3) || double.IsNaN(t3))
{
t1 = 0.0;
}
else
{
t1 = t3;
}
}
else
{
t1 = t2;
}
}
if (double.IsInfinity(t2) || double.IsNaN(t2))
{
if (double.IsInfinity(t1) || double.IsNaN(t1))
{
if (double.IsInfinity(t3) || double.IsNaN(t3))
{
t2 = 0.0;
}
else
{
t2 = t3;
}
}
else
{
t2 = t1;
}
}
if (double.IsInfinity(t3) || double.IsNaN(t3))
{
if (double.IsInfinity(t1) || double.IsNaN(t1))
{
if (double.IsInfinity(t2) || double.IsNaN(t2))
{
t3 = 0.0;
}
else
{
t3 = t2;
}
}
else
{
t3 = t1;
}
}
// Lines intersect when s1=s2 and t1=t2 and als s1=s3 and t1=t3
if (MathUtils.equalTol(s1, s2, MathUtils.defaultTol) && MathUtils.equalTol(t1, t2, MathUtils.defaultTol) && MathUtils.equalTol(s1, s3, MathUtils.defaultTol) && MathUtils.equalTol(t1, t3, MathUtils.defaultTol))
{
// calculate intersection point
ip.X = (1 - s1) * L1.startPoint.X + s1 * L1.endPoint.X;
ip.Y = (1 - s1) * L1.startPoint.Y + s1 * L1.endPoint.Y;
ip.Z = (1 - s1) * L1.startPoint.Z + s1 * L1.endPoint.Z;
intersectionPoint = ip;
if ((0 <= s1 && s1 <= 1) && (0 <= t1 && t1 <= 1))
{
// If the segments intersect s and t have to be between 0 and 1
mode = LineSegmentIntersectEnum.IntersectedWithinSegments;
return(true);
}
else
{
// Lines intersect but intersection occurs outside of the segments
mode = LineSegmentIntersectEnum.IntersectedOutsideSegments;
return(false);
}
}
}
return(false);
}
/// <summary>
/// Test whether 2 lines are parallel
/// </summary>
/// <param name="L1"></param>
/// <param name="L2"></param>
/// <returns></returns>
public static bool parallel(Line3D L1, Line3D L2)
{
// Parallel test must allow vectors with opposite direction as parallel too
return
(Vector3D.Parallels(L1.direction, L2.direction));
}
/// <summary>
/// Testing whether 2 line segments overlapped
/// </summary>
/// <param name="lineSegment1">First line segment</param>
/// <param name="lineSegment2">Second line segment</param>
/// <param name="overlappedSegment">The resulting overlapped line segment</param>
/// <param name="mode">The enumeration of the result</param>
/// <returns></returns>
public static bool overlap(LineSegment3D lineSegment1, LineSegment3D lineSegment2, out LineSegment3D overlappedSegment, out LineSegmentOverlapEnum mode)
{
mode = LineSegmentOverlapEnum.Undefined;
overlappedSegment = lineSegment1;
// First check whether they have the same lineDirection (absolute: -v = +v for overlap test)
if (!Line3D.parallel(lineSegment1.baseLine, lineSegment2.baseLine))
{
return(false);
}
// The lines are parallel, now check whether there is at least one point falls in the segment
// Test points in line 2 on line 1
LineSegmentOnSegmentEnum p1l1_s, p2l1_s;
LineSegmentOnSegmentEnum p1l2_s, p2l2_s;
bool p1l1 = isInSegment(lineSegment1, lineSegment2.startPoint, out p1l1_s);
bool p2l1 = isInSegment(lineSegment1, lineSegment2.endPoint, out p2l1_s);
if (p1l1 && p2l1)
{
if ((p1l1_s == p2l1_s && p2l1_s == LineSegmentOnSegmentEnum.InsideSegment) ||
(p1l1_s == LineSegmentOnSegmentEnum.CoincideEndSegment && p2l1_s == LineSegmentOnSegmentEnum.InsideSegment) ||
(p1l1_s == LineSegmentOnSegmentEnum.InsideSegment && p2l1_s == LineSegmentOnSegmentEnum.CoincideEndSegment))
{
mode = LineSegmentOverlapEnum.SubSegment;
}
if (p1l1_s == p2l1_s && p1l1_s == LineSegmentOnSegmentEnum.CoincideEndSegment)
{
mode = LineSegmentOverlapEnum.ExactlyOverlap;
}
overlappedSegment = lineSegment2;
return(true);
}
else if (p1l1 || p2l1)
{
if (p1l1_s == LineSegmentOnSegmentEnum.CoincideEndSegment || p2l1_s == LineSegmentOnSegmentEnum.CoincideEndSegment)
{
mode = LineSegmentOverlapEnum.Touch;
// Zero lenth line segments = a point, a valid data
if (p1l1)
{
overlappedSegment = new LineSegment3D(lineSegment2.startPoint, lineSegment2.startPoint);
}
if (p2l1)
{
overlappedSegment = new LineSegment3D(lineSegment2.endPoint, lineSegment2.endPoint);
}
}
if (p1l1_s == LineSegmentOnSegmentEnum.InsideSegment || p2l1_s == LineSegmentOnSegmentEnum.InsideSegment)
{
bool p1l2 = isInSegment(lineSegment2, lineSegment1.startPoint, out p1l2_s);
bool p2l2 = isInSegment(lineSegment2, lineSegment1.endPoint, out p2l2_s);
if (p1l1_s == LineSegmentOnSegmentEnum.InsideSegment && p1l2_s == LineSegmentOnSegmentEnum.InsideSegment)
{
overlappedSegment = new LineSegment3D(lineSegment2.startPoint, lineSegment1.startPoint);
}
if (p2l1_s == LineSegmentOnSegmentEnum.InsideSegment && p1l2_s == LineSegmentOnSegmentEnum.InsideSegment)
{
overlappedSegment = new LineSegment3D(lineSegment2.endPoint, lineSegment1.startPoint);
}
if (p1l1_s == LineSegmentOnSegmentEnum.InsideSegment && p2l2_s == LineSegmentOnSegmentEnum.InsideSegment)
{
overlappedSegment = new LineSegment3D(lineSegment2.startPoint, lineSegment1.endPoint);
}
if (p2l1_s == LineSegmentOnSegmentEnum.InsideSegment && p2l2_s == LineSegmentOnSegmentEnum.InsideSegment)
{
overlappedSegment = new LineSegment3D(lineSegment2.endPoint, lineSegment1.endPoint);
}
mode = LineSegmentOverlapEnum.PartiallyOverlap;
}
return(true);
}
else
{
// if both p1l1 and p2l1 are false, there is probability that the l1 are inside the l2 instead. Only this case needs to be checked since other
// cases should be covered by the previous conditional checks
bool p1l2 = isInSegment(lineSegment2, lineSegment1.startPoint, out p1l2_s);
bool p2l2 = isInSegment(lineSegment2, lineSegment1.endPoint, out p2l2_s);
if ((p1l2 && p2l2) &&
(p1l2_s == p2l2_s && p1l2_s == LineSegmentOnSegmentEnum.InsideSegment))
{
mode = LineSegmentOverlapEnum.SuperSegment;
overlappedSegment = lineSegment1;
return(true);
}
}
return(false);
}
