gov/nasa/worldwind/geom/Line.java

   1 /*
   2 Copyright (C) 2001, 2006 United States Government
   3 as represented by the Administrator of the
   4 National Aeronautics and Space Administration.
   5 All Rights Reserved.
   6 */
   7 package gov.nasa.worldwind.geom;
   8
   9 import gov.nasa.worldwind.*;
  10
  11 /**
  12  * @author Tom Gaskins
  13  * @version $Id: Line.java 1749 2007-05-06 19:48:14Z tgaskins $
  14  */
  15 public final class Line// Instances are immutable
  16 {
  17     private final Point origin;
  18     private final Point direction;
  19
  20     /**
  21      * @param origin
  22      * @param direction
  23      * @throws IllegalArgumentException if <code>origin</code> is null, or <code>direction</code> is null or has zero
  24      *                                  length
  25      */
  26     public Line(Point origin, Point direction)
  27     {
  28         String message = null;
  29         if (origin == null)
  30             message = "nullValue.OriginIsNull";
  31         else if (direction == null)
  32             message = "nullValue.DirectionIsNull";
  33         else if (direction.length() <= 0)
  34             message = "geom.Line.DirectionIsZeroVector";
  35         if (message != null)
  36         {
  37             message = WorldWind.retrieveErrMsg(message);
  38             WorldWind.logger().log(java.util.logging.Level.FINE, message);
  39             throw new IllegalArgumentException(message);
  40         }
  41
  42         this.origin = origin;
  43         this.direction = direction;
  44     }
  45
  46     public final Point getDirection()
  47     {
  48         return direction;
  49     }
  50
  51     public final Point getOrigin()
  52     {
  53         return origin;
  54     }
  55
  56     public final Point getPointAt(double t)
  57     {
  58         return Point.fromOriginAndDirection(t, this.direction, this.origin);
  59     }
  60
  61     public final double selfDot()
  62     {
  63         return this.origin.dot(this.direction);
  64     }
  65
  66     /**
  67      * Performs a comparison to test whether this Object is internally identical to the other Object <code>o</code>.
  68      * This method takes into account both direction and origin, so two lines which may be equivalent may not be
  69      * considered equal.
  70      *
  71      * @param o the object to be compared against.
  72      * @return true if these two objects are equal, false otherwise
  73      */
  74     @Override
  75     public final boolean equals(Object o)
  76     {
  77         if (this == o)
  78             return true;
  79         if (o == null || getClass() != o.getClass())
  80             return false;
  81
  82         final gov.nasa.worldwind.geom.Line line = (gov.nasa.worldwind.geom.Line) o;
  83
  84         if (!direction.equals(line.direction))
  85             return false;
  86         if (!line.origin.equals(origin))
  87             return false;
  88
  89         return true;
  90     }
  91
  92     @Override
  93     public final int hashCode()
  94     {
  95         int result;
  96         result = origin.hashCode();
  97         result = 29 * result + direction.hashCode();
  98         return result;
  99     }
 100
 101     public String toString()
 102     {
 103         return "Origin: " + this.origin + ", Direction: " + this.direction;
 104     }
 105
 106     /**
 107      * Calculate the shortests distance between this line and a specified <code>Point</code>. This method returns a
 108      * positive distance.
 109      *
 110      * @param p the <code>Point</code> whose distance from this <code>Line</code> will be calculated
 111      * @return the distance between this <code>Line</code> and the specified <code>Point</code>
 112      * @throws IllegalArgumentException if <code>p</code> is null
 113      */
 114     public final double distanceTo(Point p)
 115     {
 116         if (p == null)
 117         {
 118             String message = WorldWind.retrieveErrMsg("nullValue.PointIsNull");
 119             WorldWind.logger().log(java.util.logging.Level.FINE, message);
 120             throw new IllegalArgumentException(message);
 121         }
 122
 123         Point origin = this.getOrigin();
 124         Point sideB = origin.subtract(p); // really a vector
 125
 126         double distanceToOrigin = sideB.dot(this.getDirection());
 127         double divisor = distanceToOrigin / this.getDirection().selfDot();
 128
 129         Point sideA = this.getDirection().multiply(divisor);
 130
 131         double aSquared = sideA.selfDot();
 132         double bSquared = sideB.selfDot();
 133
 134         return Math.sqrt(bSquared - aSquared);
 135     }
 136 }