gt:       return((double) (Math.acos( vDot )));
context: /*
   * $RCSfile: Vector3d.java,v $
   *
   * Copyright 1997-2008 Sun Microsystems, Inc.  All Rights Reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Sun designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Sun in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   *
   * $Revision: 1.5 $
   * $Date: 2008/02/28 20:18:51 $
   * $State: Exp $
   */
  
  package javax.vecmath;
  
  import java.lang.Math;
  
  /**
   * A 3-element vector that is represented by double-precision floating point 
   * x,y,z coordinates.  If this value represents a normal, then it should
   * be normalized.
   *
   */
  public class Vector3d extends Tuple3d implements java.io.Serializable {
  
      // Combatible with 1.1
      static final long serialVersionUID = 3761969948420550442L;
  
      /**
       * Constructs and initializes a Vector3d from the specified xyz coordinates.
       * @param x the x coordinate
       * @param y the y coordinate
       * @param z the z coordinate
       */
      public Vector3d(double x, double y, double z)
      {
          super(x,y,z);
      }
  
  
      /**
       * Constructs and initializes a Vector3d from the array of length 3.
       * @param v the array of length 3 containing xyz in order
       */
      public Vector3d(double[] v)
      {
         super(v);
      }
  
  
      /**
       * Constructs and initializes a Vector3d from the specified Vector3d.
       * @param v1 the Vector3d containing the initialization x y z data
       */
      public Vector3d(Vector3d v1)
      {
           super(v1);
      }
  
  
      /**
       * Constructs and initializes a Vector3d from the specified Vector3f.
       * @param v1 the Vector3f containing the initialization x y z data
       */
      public Vector3d(Vector3f v1)
      {
         super(v1);
      }
  
  
      /**
       * Constructs and initializes a Vector3d from the specified Tuple3f.
       * @param t1 the Tuple3f containing the initialization x y z data
       */  
      public Vector3d(Tuple3f t1) 
      {
         super(t1);
      }
  
  
      /**
       * Constructs and initializes a Vector3d from the specified Tuple3d.
       * @param t1 the Tuple3d containing the initialization x y z data 
       */  
      public Vector3d(Tuple3d t1) 
      {
         super(t1); 
      }
  
  
      /**
       * Constructs and initializes a Vector3d to (0,0,0).
       */
      public Vector3d()
      {
         super();
      }
  
  
     /**
       * Sets this vector to the vector cross product of vectors v1 and v2.
       * @param v1 the first vector
       * @param v2 the second vector
       */
      public final void cross(Vector3d v1, Vector3d v2)
      { 
          double x,y;
  
          x = v1.y*v2.z - v1.z*v2.y;
          y = v2.x*v1.z - v2.z*v1.x;
          this.z = v1.x*v2.y - v1.y*v2.x;
          this.x = x;
          this.y = y;
      }
  
  
      /**
       * Sets the value of this vector to the normalization of vector v1.
       * @param v1 the un-normalized vector
       */
      public final void normalize(Vector3d v1)
      {
          double norm;
  
          norm = 1.0/Math.sqrt(v1.x*v1.x + v1.y*v1.y + v1.z*v1.z);
          this.x = v1.x*norm;
          this.y = v1.y*norm;
          this.z = v1.z*norm;
      }
  
  
      /**
       * Normalizes this vector in place.
       */
      public final void normalize()
      {
          double norm;
  
          norm = 1.0/Math.sqrt(this.x*this.x + this.y*this.y + this.z*this.z);
          this.x *= norm;
          this.y *= norm;
          this.z *= norm;
      }
  
  
    /**
     * Returns the dot product of this vector and vector v1.
     * @param v1 the other vector
     * @return the dot product of this and v1
     */
    public final double dot(Vector3d v1)
      {
        return (this.x*v1.x + this.y*v1.y + this.z*v1.z);
      }
  
  
      /**
       * Returns the squared length of this vector.
       * @return the squared length of this vector
       */
      public final double lengthSquared()
      {
          return (this.x*this.x + this.y*this.y + this.z*this.z);
      }
  
  
      /**
       * Returns the length of this vector.
       * @return the length of this vector
       */
      public final double length()
      {
          return Math.sqrt(this.x*this.x + this.y*this.y + this.z*this.z);
      }
  
  
    /** 
      *   Returns the angle in radians between this vector and the vector
      *   parameter; the return value is constrained to the range [0,PI]. 
      *   @param v1    the other vector 
      *   @return   the angle in radians in the range [0,PI] 
      */   
     public final double angle(Vector3d v1) 
     { 
        double vDot = this.dot(v1) / ( this.length()*v1.length() );
        if( vDot < -1.0) vDot = -1.0;
        if( vDot >  1.0) vDot =  1.0;
  