1 package org.lcsim.recon.tracking.spacegeom;
2
3 /** A point in 2-space. The default Space point is at the origin.
4 * Derived classes can be used to set values in cartesian or cylindrical
5 * coordinates. Point is set in the constructor and cannot be changed.
6 * The methods simply return different coordinates.
7 * Transformations (translations, rotations, etc) are carried out by
8 * external functions which return new TwoSpacePoints.
9 *@author Norman A. Graf
10 *@version 1.0
11 */
12 public class TwoSpacePoint
13 {
14
15 // data
16 protected double _x;
17 protected double _y;
18 protected double _xy;
19 protected double _phi;
20
21 // static methods
22
23 // Return if two doubles are close enough to be considered equal.
24 // This is used to compare components for operator==.
25 private static boolean equal(double x1, double x2)
26 {
27 // double maxdif = 2.0*std::numeric_limits<double>::epsilon();
28 double maxdif = 5.0e-16;
29 double num = 2.0*(x2-x1);
30 double den = x2 + x1;
31 double dif = Math.abs(num/den);
32 return dif <= maxdif;
33 }
34
35 // methods
36
37 /** Default constructor.
38 * Sets point to be the origin with phi = 0.
39 */
40 public TwoSpacePoint( )
41 {
42 _x = _y = 0.0;
43 _xy = 0.0;
44 _phi = 0.0;
45 }
46
47 // Cartesian x.
48 /**
49 * @return Cartesian x coordinate
50 */
51 public double x( )
52 {
53 return _x;
54 }
55
56 // Cartesian y.
57 /**
58 * @return Cartesian y coordinate
59 */
60 public double y( )
61 {
62 return _y;
63 }
64
65 // Cylindrical r.
66 /**
67 * @return Cylindrical radius coordinate
68 */
69 public double rxy( )
70 {
71 return _xy;
72 }
73
74 // Cylindrical phi.
75 /**
76 * @return Cylindrical phi coordinate
77 */
78 public double phi( )
79 {
80 return _phi;
81 }
82
83 // cos(phi)
84 /**
85 * @return Cosine of Cylindrical phi coordinate
86 */
87 public double cosPhi( )
88 {
89 if ( _xy != 0. ) return _x/_xy;
90 return Math.cos(_phi);
91 }
92
93 // sin(phi)
94 /**
95 * @return Sine of Cylindrical phi coordinate
96 */
97 public double sinPhi( )
98 {
99 if ( _xy != 0. ) return _y/_xy;
100 return Math.sin(_phi);
101 }
102
103 /**
104 * @return String representation of this class
105 */
106 public String toString()
107 {
108 return "TwoSpacePoint: \n x: " + x() + " \n"
109 + " y: " + y() + "\n"
110 + " rxy: " + rxy() + "\n"
111 + " phi: " + phi();
112 }
113
114 /** Checks object equality
115 * @param tsp TwoSpacePoint to compare with for equality
116 * @return true of this TwoSpacePoint equals tsp
117 */
118 public boolean equals( TwoSpacePoint tsp )
119 {
120 return ( equal(x(),tsp.x()) && equal(y(),tsp.y()) );
121 }
122
123 /** Checks object inequality
124 * @param tsp TwoSpacePoint to compare with for inequality
125 * @return true of this TwoSpacePoint does not equal tsp
126 */
127 public boolean notEquals( TwoSpacePoint tsp )
128 {
129 return !equals(tsp);
130 }
131
132 // Return the distance between two space points.
133 /**
134 * @param tsp1 first TwoSpacePoint
135 * @param tsp2 second TwoSpacePoint
136 * @return Two diensional Euclidean distance between points
137 */
138 public static double distance(TwoSpacePoint tsp1, TwoSpacePoint tsp2 )
139 {
140 double dx = tsp2.x() - tsp1.x();
141 double dy = tsp2.y() - tsp1.y();
142 return Math.sqrt( dx*dx + dy*dy );
143 }
144
145 }