LineSegment2D Class Reference

2D line segment. More...

#include <LineSegment2D.h>

Inheritance diagram for LineSegment2D:

Public Member Functions
	LineSegment2D (const HepGeom::Point3D< double > &point1, const HepGeom::Point3D< double > &point2)
	Constructor.
	~LineSegment2D ()
	Destructor.
int	findIntersection (const Line2D &line, HepGeom::Point3D< double > *intersection) const
	Find intersection with a line.
int	findIntersection (const LineSegment2D &lineSegment, HepGeom::Point3D< double > *intersection) const
	Find intersection with a line segment.
int	findIntersection (const Circle2D &circle, HepGeom::Point3D< double > intersections[2]) const
	Find intersections with a circle.
int	findIntersection (const Arc2D &arc, HepGeom::Point3D< double > intersections[2]) const
	Find intersections with an arc.
bool	tWithinRange (double t) const
	Check if t is within the line segment (0 <= t <= 1).
const HepGeom::Point3D< double > &	getInitialPoint () const
	Get initial point.
const HepGeom::Vector3D< double > &	getVector () const
	Get vector.
int	findIntersection (const Line2D &line, HepGeom::Point3D< double > *intersection, double t[2]) const
	Find intersection with a line.

Protected Member Functions
int	findIntersection (const Circle2D &circle, HepGeom::Point3D< double > intersections[2], double t[2], double angles[2]) const
	Find intersections with a circle.
int	selectIntersections (HepGeom::Point3D< double > *intersections, bool *condition, int n) const
	Select intersections.

Protected Attributes
HepGeom::Point3D< double >	m_Point
	Initial point.
HepGeom::Vector3D< double >	m_Vector
	Vector.

Detailed Description

2D line segment.

Equation: m_Point + m_Vector * t, t = [0, 1].

Definition at line 28 of file LineSegment2D.h.

Constructor & Destructor Documentation

LineSegment2D()

LineSegment2D	(	const HepGeom::Point3D< double > &	point1,
		const HepGeom::Point3D< double > &	point2
	)

Constructor.

Parameters

[in]	point1	First point.
[in]	point2	Second point.

Definition at line 14 of file LineSegment2D.cc.

                                                                         :
  Line2D(point1.x(), point1.y(),
         point2.x() - point1.x(), point2.y() - point1.y())
{
}

~LineSegment2D()

~LineSegment2D

(

)

Destructor.

Definition at line 21 of file LineSegment2D.cc.

{
}

Member Function Documentation

findIntersection() [1/6]

int findIntersection	(	const Arc2D &	arc,
		HepGeom::Point3D< double >	intersections[2]
	)		const

Find intersections with an arc.

Parameters

[in]	arc	Arc.
[out]	intersections	Intersections.

Returns

Number of intersections (0, 1 or 2).

Definition at line 67 of file LineSegment2D.cc.

{
  int i, n;
  double t[2], angles[2];
  bool condition[2];
  n = Line2D::findIntersection(arc, intersections, t, angles);
  for (i = 0; i < n; i++)
    condition[i] = tWithinRange(t[i]) && arc.angleWithinRange(angles[i]);
  return selectIntersections(intersections, condition, n);
}

findIntersection() [2/6]

int findIntersection	(	const Circle2D &	circle,
		HepGeom::Point3D< double >	intersections[2]
	)		const

Find intersections with a circle.

Parameters

[in]	circle	Circle.
[out]	intersections	Intersections.

Returns

Number of intersections (0, 1 or 2).

Definition at line 54 of file LineSegment2D.cc.

{
  int i, n;
  double t[2], angles[2];
  bool condition[2];
  n = Line2D::findIntersection(circle, intersections, t, angles);
  for (i = 0; i < n; i++)
    condition[i] = tWithinRange(t[i]);
  return selectIntersections(intersections, condition, n);
}

findIntersection() [3/6]

int findIntersection ( const Circle2D &  circle, HepGeom::Point3D< double >  intersections[2], double  t[2], double  angles[2]  ) const

protectedinherited

Find intersections with a circle.

Parameters

[in]	circle	Circle.
[out]	intersections	Intersections.
[out]	t	Values of t for intersection points.
[out]	angles	Values of angles for intersection points.

Returns

Number of intersections (0, 1 or 2).

Definition at line 95 of file Line2D.cc.

{
  int i;
  double a, b, c, d, x0, y0;
  const HepGeom::Point3D<double>& circleCenter = circle.getCenter();
  x0 = m_Point.x() - circleCenter.x();
  y0 = m_Point.y() - circleCenter.y();
  a = m_Vector.x() * m_Vector.x() + m_Vector.y() * m_Vector.y();
  b = 2.0 * (m_Vector.x() * x0 + m_Vector.y() * y0);
  c = x0 * x0 + y0 * y0 - circle.getRadius() * circle.getRadius();
  d = b * b - 4 * a * c;
  if (d < 0)
    return 0;
  if (d == 0) {
    t[0] = -b / (2.0 * a);
    intersections[0].setX(m_Point.x() + m_Vector.x() * t[0]);
    intersections[0].setY(m_Point.y() + m_Vector.y() * t[0]);
    intersections[0].setZ(0);
    angles[0] = atan2(intersections[0].y() - circleCenter.y(),
                      intersections[0].x() - circleCenter.x());
    return 1;
  }
  t[0] = (-b - sqrt(d)) / (2.0 * a);
  t[1] = (-b + sqrt(d)) / (2.0 * a);
  for (i = 0; i < 2; i++) {
    intersections[i].setX(m_Point.x() + m_Vector.x() * t[i]);
    intersections[i].setY(m_Point.y() + m_Vector.y() * t[i]);
    intersections[i].setZ(0);
    angles[i] = atan2(intersections[i].y() - circleCenter.y(),
                      intersections[i].x() - circleCenter.x());
  }
  return 2;
}

findIntersection() [4/6]

int findIntersection	(	const Line2D &	line,
		HepGeom::Point3D< double > *	intersection
	)		const

Find intersection with a line.

Parameters

[in]	line	Line.
[out]	intersection	Intersection.

Returns

Number of intersections (0 or 1).

Definition at line 25 of file LineSegment2D.cc.

{
  int n;
  double t[2];
  bool condition;
  n = Line2D::findIntersection(line, intersection, t);
  if (n == 0)
    return 0;
  condition = tWithinRange(t[0]);
  return selectIntersections(intersection, &condition, 1);
}

findIntersection() [5/6]

int findIntersection ( const Line2D &  line, HepGeom::Point3D< double > *  intersection, double  t[2]  ) const

inherited

Find intersection with a line.

Parameters

[in]	line	Line.
[out]	intersection	Intersection.
[out]	t	Values of t for intersection point (t[0] - this line, t[1] - line from argument).

Returns

Number of intersections (0 or 1).

If (*this) and line are the same line then 0 is returned.

Definition at line 65 of file Line2D.cc.

{
  double a1, a2, b1, b2, c1, c2, d, dt[2];
  a1 = m_Vector.x();
  a2 = m_Vector.y();
  b1 = -line.getVector().x();
  b2 = -line.getVector().y();
  c1 = m_Point.x() - line.getInitialPoint().x();
  c2 = m_Point.y() - line.getInitialPoint().y();
  d = a1 * b2 - a2 * b1;
  /* Same line (d == 0, dt[i] == 0) considered as no intersection! */
  if (d == 0)
    return 0;
  dt[0] = c1 * b2 - c2 * b1;
  dt[1] = a1 * c2 - a2 * c1;
  t[0] = -dt[0] / d;
  t[1] = -dt[1] / d;
  intersection->setX(m_Point.x() + m_Vector.x() * t[0]);
  intersection->setY(m_Point.y() + m_Vector.y() * t[0]);
  intersection->setZ(0);
  return 1;
}

findIntersection() [6/6]

int findIntersection	(	const LineSegment2D &	lineSegment,
		HepGeom::Point3D< double > *	intersection
	)		const

Find intersection with a line segment.

Parameters

[in]	lineSegment	Line segment.
[out]	intersection	Intersection.

Returns

Number of intersections (0 or 1).

Definition at line 40 of file LineSegment2D.cc.

{
  int n;
  double t[2];
  bool condition;
  n = Line2D::findIntersection(lineSegment, intersection, t);
  if (n == 0)
    return 0;
  condition = tWithinRange(t[0]) && lineSegment.tWithinRange(t[1]);
  return selectIntersections(intersection, &condition, 1);
}

getInitialPoint()

const HepGeom::Point3D< double > & getInitialPoint ( ) const

inlineinherited

Get initial point.

Definition at line 51 of file Line2D.h.

      {
        return m_Point;
      }

getVector()

const HepGeom::Vector3D< double > & getVector ( ) const

inlineinherited

Get vector.

Definition at line 59 of file Line2D.h.

      {
        return m_Vector;
      }

selectIntersections()

int selectIntersections ( HepGeom::Point3D< double > *  intersections, bool *  condition, int  n  ) const

protectedinherited

Select intersections.

Parameters

[in,out]	intersections	Intersections.
[in]	condition	Selection condition.
[in]	n	Number of intersections.

Returns

Number of selected intersections.

Definition at line 132 of file Line2D.cc.

{
  int i, j;
  j = 0;
  for (i = 0; i < n; i++) {
    if (condition[i]) {
      if (i != j)
        intersections[j] = intersections[i];
      j++;
    }
  }
  return j;
}

tWithinRange()

bool tWithinRange

(

double

t

)

const

Check if t is within the line segment (0 <= t <= 1).

Parameters

[in]

t

Line parameter.

Definition at line 80 of file LineSegment2D.cc.

{
  return (t >= 0 && t <= 1);
}

Member Data Documentation

m_Point

HepGeom::Point3D<double> m_Point

protectedinherited

Initial point.

Definition at line 130 of file Line2D.h.

m_Vector

HepGeom::Vector3D<double> m_Vector

protectedinherited

Vector.

Definition at line 133 of file Line2D.h.

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The documentation for this class was generated from the following files:

• klm/eklm/geometry/include/LineSegment2D.h
• klm/eklm/geometry/src/LineSegment2D.cc