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.util.Logging;
  10
  11 /**
  12  * @author Tom Gaskins
  13  * @version $Id: Line.java 2471 2007-07-31 21:50:57Z tgaskins $
  14  */
  15 public final class Line// Instances are immutable
  16 {
  17     private final Vec4 origin;
  18     private final Vec4 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(Vec4 origin, Vec4 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.getLength3() <= 0)
  34             message = "Geom.Line.DirectionIsZeroVector";
  35         if (message != null)
  36         {
  37             message = Logging.getMessage(message);
  38             Logging.logger().severe(message);
  39             throw new IllegalArgumentException(message);
  40         }
  41
  42         this.origin = origin;
  43         this.direction = direction;
  44     }
  45
  46     public final Vec4 getDirection()
  47     {
  48         return direction;
  49     }
  50
  51     public final Vec4 getOrigin()
  52     {
  53         return origin;
  54     }
  55
  56     public final Vec4 getPointAt(double t)
  57     {
  58         return Vec4.fromLine3(this.origin, t, this.direction);
  59     }
  60
  61     public final double selfDot()
  62     {
  63         return this.origin.dot3(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         //noinspection RedundantIfStatement
  87         if (!line.origin.equals(origin))
  88             return false;
  89
  90         return true;
  91     }
  92
  93     @Override
  94     public final int hashCode()
  95     {
  96         int result;
  97         result = origin.hashCode();
  98         result = 29 * result + direction.hashCode();
  99         return result;
 100     }
 101
 102     public String toString()
 103     {
 104         return "Origin: " + this.origin + ", Direction: " + this.direction;
 105     }
 106
 107     /**
 108      * Calculate the shortests distance between this line and a specified <code>Vec4</code>. This method returns a
 109      * positive distance.
 110      *
 111      * @param p the <code>Vec4</code> whose distance from this <code>Line</code> will be calculated
 112      * @return the distance between this <code>Line</code> and the specified <code>Vec4</code>
 113      * @throws IllegalArgumentException if <code>p</code> is null
 114      */
 115     public final double distanceTo(Vec4 p)
 116     {
 117         if (p == null)
 118         {
 119             String message = Logging.getMessage("nullValue.PointIsNull");
 120             Logging.logger().severe(message);
 121             throw new IllegalArgumentException(message);
 122         }
 123
 124         Vec4 origin = this.origin;
 125         Vec4 sideB = origin.subtract3(p); // really a vector
 126
 127         double distanceToOrigin = sideB.dot3(this.direction);
 128         double divisor = distanceToOrigin / this.direction.getLengthSquared3();
 129
 130         Vec4 sideA = this.direction.multiply3(divisor);
 131
 132         double aSquared = sideA.getLengthSquared3();
 133         double bSquared = sideB.getLengthSquared3();
 134
 135         return Math.sqrt(bSquared - aSquared);
 136     }
 137 }