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annotate flys-artifacts/src/main/java/de/intevation/flys/artifacts/geom/VectorUtils.java @ 3227:ed07dd55f487

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Fixed various bugs (package declarations, moved classes to correct places). flys-artifacts/trunk@4854 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author Ingo Weinzierl <ingo.weinzierl@intevation.de>
date Tue, 03 Jul 2012 08:46:14 +0000
parents 5642a83420f2
children
rev   line source
3227
ed07dd55f487 Fixed various bugs (package declarations, moved classes to correct places).
Ingo Weinzierl <ingo.weinzierl@intevation.de>
parents: 3076
diff changeset
1 package de.intevation.flys.artifacts.geom;
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2
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3 import java.awt.geom.Point2D;
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4
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5 public final class VectorUtils
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6 {
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7 public static final double EPSILON = 1e-4;
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8
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9 private VectorUtils() {
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10 }
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11
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12 public static final double X(Point2D p) {
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13 return p.getX();
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14 }
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15
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16 public static final double Y(Point2D p) {
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17 return p.getY();
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18 }
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19
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20 public static final Point2D sub(Point2D a, Point2D b) {
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21 return new Point2D.Double(X(a)-X(b), Y(a)-Y(b));
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22 }
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23
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24 public static final double dot(Point2D a, Point2D b) {
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25 return X(a)*X(b) + Y(a)*Y(b);
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26 }
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27
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28 public static final Point2D add(Point2D a, Point2D b) {
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29 return new Point2D.Double(X(a)+X(b), Y(a)+Y(b));
5eec623db50a Polygon2D: moved 2D vector operation to separate class.
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30 }
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31
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32 public static final Point2D negate(Point2D a) {
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33 return new Point2D.Double(-X(a), -Y(a));
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34 }
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35
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36 public static final Point2D ortho(Point2D a) {
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37 return new Point2D.Double(-Y(a), X(a));
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38 }
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39
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40 public static final Point2D scale(Point2D a, double s) {
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41 return new Point2D.Double(s*X(a), s*Y(a));
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42 }
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43
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44 public static final double lengthSq(Point2D a) {
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45 double x = X(a);
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46 double y = Y(a);
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47 return x*x + y*y;
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48 }
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49
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50 public static final double length(Point2D a) {
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51 return Math.sqrt(lengthSq(a));
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52 }
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53
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54 public static final Point2D normalize(Point2D a) {
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55 double length = length(a);
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56 return length != 0d
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57 ? scale(a, 1d/length)
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58 : new Point2D.Double(X(a), Y(a));
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59 }
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60
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61 public static final double L1(Point2D a, Point2D b) {
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62 return Math.abs(X(a)-X(b)) + Math.abs(Y(a)-Y(b));
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63 }
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64
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65 public static final boolean collinear(Point2D a, Point2D b, Point2D c) {
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66 double x1 = X(a);
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67 double y1 = Y(a);
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68 double x2 = X(b);
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69 double y2 = Y(b);
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70 double x3 = X(c);
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71 double y3 = Y(c);
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72
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73 return Math.abs((x2-x1)*(y3-y1)-(y2-y1)*(x3-x1)) < EPSILON;
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74 }
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75
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76 public static boolean epsilonEquals(Point2D a, Point2D b) {
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77 return Math.abs(X(a)-X(b)) < EPSILON
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78 && Math.abs(Y(a)-Y(b)) < EPSILON;
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79 }
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80
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81 public static final Point2D intersection(
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82 Point2D p1, Point2D p2,
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83 Point2D p3, Point2D p4
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84 ) {
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85 double x1 = X(p1);
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86 double y1 = Y(p1);
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87 double x2 = X(p2);
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88 double y2 = Y(p2);
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89 double x3 = X(p3);
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90 double y3 = Y(p3);
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91 double x4 = X(p4);
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92 double y4 = Y(p4);
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93
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94 // Compute a1, b1, c1, where line joining points 1 and 2
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95 // is "a1 x + b1 y + c1 = 0".
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96 double a1 = y2 - y1;
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97 double b1 = x1 - x2;
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98 double c1 = x2*y1 - x1*y2;
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99
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100 // Compute r3 and r4.
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101 double r3 = a1*x3 + b1*y3 + c1;
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102 double r4 = a1*x4 + b1*y4 + c1;
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103
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104 if (r3 != 0d && r4 != 0d && r3*r4 >= 0) {
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105 return null;
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106 }
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107
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108 // Compute a2, b2, c2
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109 double a2 = y4 - y3;
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110 double b2 = x3 - x4;
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111 double c2 = (x4 * y3) - (x3 * y4);
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112
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113 // Compute r1 and r2
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114 double r1 = a2*x1 + b2*y1 + c2;
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115 double r2 = a2*x2 + b2*y2 + c2;
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parents: 1799
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116
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
117 if (r1 != 0d && r2 != 0d && r1*r2 >= 0) {
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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118 return null;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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119 }
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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120
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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121 // Line segments intersect: compute intersection point.
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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122 double denom = a1*b2 - a2*b1;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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123
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
124 if (denom == 0d) { // collinear
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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125 return null;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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126 }
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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127
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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128 double offset = Math.abs(denom)/2d;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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129
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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130 // The denom/2 is to get rounding instead of truncating. It
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
131 // is added or subtracted to the numerator, depending upon the
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
132 // sign of the numerator.
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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133 double num = b1*c2 - b2*c1;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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134
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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135 double x = num < 0d
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
136 ? (num - offset)/denom
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
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137 : (num + offset)/denom;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
138
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
139 num = a2*c1 - a1*c2;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
140
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
141 double y = num < 0d
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
142 ? (num - offset)/denom
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
143 : (num + offset)/denom;
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
144
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
145 return new Point2D.Double(x, y);
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
146 }
6f83d9d434f2 Polygon2D: Generate polygons for trivial cases.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1799
diff changeset
147
1797
5eec623db50a Polygon2D: moved 2D vector operation to separate class.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents:
diff changeset
148 }
3076
5642a83420f2 FLYS artifacts: Removed trailing whitespace.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
parents: 1801
diff changeset
149 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :
http://dive4elements.wald.intevation.org