Android Open Source - 4est Quaternion

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The source code is released under:
MIT License
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Java Source Code

package com.wordsaretoys.rise.geometry;
/*from www .j  av a  2  s . c om*/

/**
 * represent quaternion in 3-space plus standard operations
 * 
 * @author chris
 *
 */
public class Quaternion {
  
  public float x;
  public float y;
  public float z;
  public float w;
  
  /**
   * create new quaternion
   * @param x, y, z rotation axis
   * @param w rotation around axis
   */
  public Quaternion(float x, float y, float z, float w) {
    set(x, y, z, w);
  }
  
  public Quaternion() {
    set(0, 0, 0, 0);
  }
  
  /**
   * set the components of the quaternion
   * @param x, y, z rotation axis
   * @param w rotation around axis
   * @return self
   */
  public Quaternion set(float x, float y, float z, float w) {
    this.x = x;
    this.y = y;
    this.z = z;
    this.w = w;
    return this;
  }
  
  /**
   * copy components from another quaternion
   * @param q quaternion
   * @return self
   */
  public Quaternion copy(Quaternion q) { 
    x = q.x;
    y = q.y;
    z = q.z;
    w = q.w;
    return this;
  }
  
  /**
   * multiply this quaternion by another
   * @param q quaternion
   * @return self
   */
  public Quaternion mul(Quaternion q) {
    float tx = x;
    float ty = y;
    float tz = z;
    float tw = w;
    x = tw * q.x + tx * q.w + ty * q.z - tz * q.y;
    y = tw * q.y + ty * q.w + tz * q.x - tx * q.z;
    z = tw * q.z + tz * q.w + tx * q.y - ty * q.x;
    w = tw * q.w - tx * q.x - ty * q.y - tz * q.z;
    return this;
  }
  
  /**
   * generate inverse of quaternion
   * @return self
   */
  public Quaternion neg() {
    return set(-x, -y, -z, w); 
  }
  
  /**
   * normalize the quaternion
   * @return self
   */
  public Quaternion norm() {
    float mag = (float)Math.sqrt(x * x + y * y + z * z + w * w);
    return set(x / mag, y / mag, z / mag, w / mag);
  }
  
  /**
   * generate matrix from quaternion
   * @param m 4x4 matrix laid out in 16-element array
   * @return filled array
   */
  public float[] toMatrix(float[] m) {
    m[0] = (float)(1.0 - 2.0 * (y * y + z * z));
    m[1] = (float)(2.0 * (x * y + z * w));
    m[2] = (float)(2.0 * (x * z - y * w));
    m[3] = 0;
    m[4] = (float)(2.0 * (x * y - z * w));
    m[5] = (float)(1.0 - 2.0 * (x * x + z * z));
    m[6] = (float)(2.0 * (z * y + x * w));
    m[7] = 0;
    m[8] = (float)(2.0 * (x * z + y * w));
    m[9] = (float)(2.0 * (y * z - x * w));
    m[10] = (float)(1.0 - 2.0 * (x * x + y * y));
    m[11] = 0;
    m[12] = 0;
    m[13] = 0;
    m[14] = 0;
    m[15] = 1;
    return m;
  }
  
  /**
   * generate matrix from quaternion
   * @param m 3x3 matrix laid out in 9-element array
   * @return filled array
   */
  public float[] toMatrix3(float[] m) {
    m[0] = (float)(1.0 - 2.0 * (y * y + z * z));
    m[1] = (float)(2.0 * (x * y + z * w));
    m[2] = (float)(2.0 * (x * z - y * w));
    m[3] = (float)(2.0 * (x * y - z * w));
    m[4] = (float)(1.0 - 2.0 * (x * x + z * z));
    m[5] = (float)(2.0 * (z * y + x * w));
    m[6] = (float)(2.0 * (x * z + y * w));
    m[7] = (float)(2.0 * (y * z - x * w));
    m[8] = (float)(1.0 - 2.0 * (x * x + y * y));
    return m;
  }

  /**
   * generate quaternion from axis-angle representation
   * @param x, y, z rotation axis
   * @param ang rotation angle (in radians)
   * @return self
   */
  public Quaternion setFromAxisAngle(float x, float y, float z, float ang) {
    float ha = (float) Math.sin(ang / 2.0);
    return set(x * ha, y * ha, z * ha, (float) Math.cos(ang / 2.0));
  }
  
  /**
   * smooth interpolation between two quaternions
   * @param a first quaternion
   * @param b second quaternion
   * @param m interpolation factor
   * @return self
   */
  public Quaternion slerp(Quaternion a, Quaternion b, float m) {
    x += m * (b.x - a.x);
    y += m * (b.y - a.y);
    z += m * (b.z - a.z);
    w += m * (b.w - a.w);
    return norm();
  }

}
Java Source Code List
