DedxLine Class Reference

A class to hold the endpoints and slope of a line. More...

#include <LineHelper.h>

Public Member Functions
	DedxLine ()
	A line is definied either by a point and a slope, or by endpoints.
	DedxLine (const DedxPoint &p, const double slope)
	Construct a DedxLine from the given DedxPoint and slope.
	DedxLine (const DedxPoint &p1, const DedxPoint &p2)
	Construct a DedxLine from two DedxPoints.
double	getSlope () const
	Helper function to return the slope.
DedxPoint	intersection (const DedxLine &l)
	Find the intersection of this and another line.
bool	isVertical () const
	The m_vertical flag is used for the special case of a vertical line.
void	setVertical ()
	Mark this DedxLine as being vertical.

Private Attributes
DedxPoint	m_p1
	First endpoint.
DedxPoint	m_p2
	Second endpoint.
double	m_m
	Slope of the line.
int	m_vertical
	If the line is vertical, this is set to true.

Detailed Description

A class to hold the endpoints and slope of a line.

This class is useful in determining the path length of a track through a CDC cell.

Definition at line 83 of file LineHelper.h.

Constructor & Destructor Documentation

DedxLine() [1/3]

DedxLine ( )

inline

A line is definied either by a point and a slope, or by endpoints.

If a single point is given, both endpoints are given by the same point (length = 0). Default constructor

Definition at line 92 of file LineHelper.h.

: m_m(0), m_vertical(false) {}

DedxLine() [2/3]

DedxLine ( const DedxPoint &  p, const double  slope  )

inline

Construct a DedxLine from the given DedxPoint and slope.

Definition at line 95 of file LineHelper.h.

: m_p1(p), m_p2(p), m_m(slope), m_vertical(false) {}

DedxLine() [3/3]

DedxLine ( const DedxPoint &  p1, const DedxPoint &  p2  )

inline

Construct a DedxLine from two DedxPoints.

Definition at line 98 of file LineHelper.h.

                                                       : m_p1(p1), m_p2(p2), m_vertical(false)
    {
      //check if the line is vertical (set vertical flag if it is)
      if (p1.getX() == p2.getX()) {
        m_m = -10000.0;
        m_vertical = true;
      } else
        m_m = (p1.getY() - p2.getY()) / (p1.getX() - p2.getX());
    }

Member Function Documentation

getSlope()

double getSlope ( ) const

inline

Helper function to return the slope.

Definition at line 109 of file LineHelper.h.

{ return m_m; }

intersection()

DedxPoint intersection ( const DedxLine &  l )

inline

Find the intersection of this and another line.

Definition at line 112 of file LineHelper.h.

    {
      double x, y;
      DedxPoint intP;
 
      // First check if the lines will intersect.
      // Also check for special cases of horizontal or
      // vertical lines.
      if (m_m == l.m_m) {
        B2WARNING("Lines are parallel, will not intersect...");
        intP.setInvalid();
        intP.setPoint(0, 0);
        return intP;
      } else if (m_m == 0.0) {
        y = m_p1.getY();
        x = (y - l.m_p1.getY()) / l.m_m + l.m_p1.getX();
      } else if (l.m_m == 0.0) {
        y = l.m_p1.getY();
        x = (y - m_p1.getY()) / m_m + m_p1.getX();
      } else if (m_vertical) {
        x = m_p1.getX();
        y = l.m_p1.getY() + l.m_m * (x - l.m_p1.getX());
      } else if (l.isVertical()) {
        x = l.m_p1.getX();
        y = m_p1.getY() + m_m * (x - m_p1.getX());
      } else {
        x = ((l.m_p1.getY() - l.m_m * l.m_p1.getX()) - (m_p1.getY() - m_m * m_p1.getX())) / (m_m - l.m_m);
        y = m_p1.getY() + m_m * (x - m_p1.getX());
      }
 
      // This is the point of intersection
      intP.setPoint(x, y);
 
      // Check if the point falls outside the endpoints of the line.
      // This is useful for calculating the track length (dx).
      if ((x > m_p1.getX() && x > m_p2.getX()) ||
          (x < m_p1.getX() && x < m_p2.getX()))
        intP.setInvalid();
      if ((y > m_p1.getY() && y > m_p2.getY()) ||
          (y < m_p1.getY() && y < m_p2.getY()))
        intP.setInvalid();
 
      // Check if the DedxLine was made from a point and make sure the
      // point is not outside the cell
      if (l.m_p1.getX() == l.m_p2.getX() && l.m_p1.getY() == l.m_p2.getY() &&
          ((l.m_p1.getX() > m_p1.getX() && l.m_p1.getX() > m_p2.getX()) ||
           (l.m_p1.getX() < m_p1.getX() && l.m_p1.getX() < m_p2.getX())) &&
          ((l.m_p1.getY() > m_p1.getY() && l.m_p1.getY() > m_p2.getY()) ||
           (l.m_p1.getY() < m_p1.getY() && l.m_p1.getY() < m_p2.getY())))
        intP.setInvalid();
 
      return intP;
    }

isVertical()

bool isVertical ( ) const

inline

The m_vertical flag is used for the special case of a vertical line.

Definition at line 167 of file LineHelper.h.

{ return m_vertical; }

setVertical()

void setVertical ( )

inline

Mark this DedxLine as being vertical.

Definition at line 170 of file LineHelper.h.

{ m_vertical = true; }

Member Data Documentation

m_m

double m_m

private

Slope of the line.

Definition at line 176 of file LineHelper.h.

m_p1

DedxPoint m_p1

private

First endpoint.

Definition at line 174 of file LineHelper.h.

m_p2

DedxPoint m_p2

private

Second endpoint.

Definition at line 175 of file LineHelper.h.

m_vertical

int m_vertical

private

If the line is vertical, this is set to true.

Definition at line 177 of file LineHelper.h.

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

• reconstruction/modules/CDCDedxPID/include/LineHelper.h