/*
 * Copyright (c) 1996 CONNIE K. PENG  All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes.
 *
 */

public class Vector
{
  public float element[];

  public Vector()
  {
    element = new float[4];
    element[0] = element[1] = element[2] = 0;
    element[3] = 1;
  }

  public Vector(Vector v)
  {
    element = new float[4];
    for (int i = 0; i < 4; i++)
      element[i] = v.element[i];
  }

  public Vector(float x, float y, float z)
  {
    element = new float[4];
    element[0] = x;
    element[1] = y;
    element[2] = z;
    element[3] = 1;
  }

  public void set_element(float x, float y, float z)
  {
    element[0] = x;
    element[1] = y;
    element[2] = z;
    element[3] = 1;
  }

  public void make_vector()
  {
    element[3] = 0;
  }

  public void make_point()
  {
    element[3] = 1;
  }

  public void add(Vector v)
  {
    for (int i = 0; i < 4; i++)
      element[i] += v.element[i];
  }

  public void sub(Vector v)
  {
    for (int i = 0; i < 4; i++)
      element[i] -= v.element[i];
  }

  public Vector negative()
  {
    for (int i = 0; i < 3; i++)
      element[i] = - element[i];

    return this;
  }

  public void scale (float f)
  {
    for (int i = 0; i < 3; i++)
      element[i] *= f;
  }

  public float magnitude()
  {
    float square = 0;

    for (int i = 0; i < 3; i++)
      square += element[i] * element[i];

    return (float) Math.sqrt(square);
  }

  public float dot_product(Vector v)
  {
    float f = 0;

    for (int i = 0; i < 3; i++)
      f += element[i] * v.element[i];

    return f;
  }

  public Vector cross_product(Vector v)
  {
    Vector cross = new Vector();

    cross.element[0] = element[1] * v.element[2] -
                       element[2] * v.element[1];
    cross.element[1] = element[2] * v.element[0] -
                       element[0] * v.element[2];
    cross.element[2] = element[0] * v.element[1] -
                       element[1] * v.element[0];

    return cross;
  }

  public void orthogonal()
  {
    Matrix m = new Matrix();
    m.rotatez(90);
    this.multiply(m);
  }

  public void multiply(Matrix m)
  {
    float[] e = new float[4];

    for (int i = 0; i < 4; i++)
    {
      e[i] = 0;
      for (int j = 0; j < 4; j++)
        e[i] += element[j] * m.element[i][j];
    }

    for (int i = 0; i < 4; i++)
      element[i] = e[i];
  }

  // perspective transformation of a vector
  public void perspective(int distance)
  {
      element[0] = (element[0] / element[2]) * distance;
      element[1] = (element[1] / element[2]) * distance;
      element[2] = - 1 / element[2];
  }
 
  public void print()
  {
    System.out.print("(" + element[0] + "," + element[1] + "," +
                     element[2] + "," + element[3] + ")");
  }
}