Contains static definition for matrix math methods. : Math « Development Class « Java






Contains static definition for matrix math methods.

       
/*
 * Soya3D
 * Copyright (C) 1999-2000 Jean-Baptiste LAMY (Artiste on the web)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */


/**
 * Contains static definition for matrix math methods.
 * 
 * Here, a matrix is a float[16], and a vector or a point a float[3] (contrary to other part of Opale.Soya, where a point is 3 coords + a CoordSyst).
 * 
 * @author Artiste on the Web
 */

public class Matrix extends Object {

  private Matrix() {  }

  /**
   * The value of PI in float.
   */
  public static final float PI = (float) java.lang.Math.PI;
  
  public static final float EPSILON = 0.001f;

  public static float pow2(float f) { return f*f; }
  
  private static float[][] stock = new float[1000][];
  
  /**
   * Inverts a 4*4 matrix. Warning : this method works only if m[3] = m[7] = m[11] = 0f
   * and m[15] = 1f.
   * @param m the matrix
   * @return the inverted matrix or null if m is not invertable
   */
  public static final float[] matrixInvert(float[] m) { // Optimized!
    float[] r = matrixInvert3_3(m);
    if(r == null) return null;
    r[12] = -(m[12] * r[0] + m[13] * r[4] + m[14] * r[ 8]);
    r[13] = -(m[12] * r[1] + m[13] * r[5] + m[14] * r[ 9]);
    r[14] = -(m[12] * r[2] + m[13] * r[6] + m[14] * r[10]);
    return r;
  }
  
  /**
   * Inverts a 3*3 part of a 4*4 matrix.
   * It IS NOT a complete inversion because other values in the matrix (such as the translation part) are set to 0.
   * It isn't a bug, other classes assume this.
   * @param m the matrix that will be inverted
   * @return the inverted matrix. Value 12, 13, 14 that represent the translation are set to 0. Return null if the matrix is not invertable
   */
  public static final float[] matrixInvert3_3(float[] m) {
    float[] r = new float[16];
    float det = m[0] * (m[5] * m[10] - m[9] * m[6])
              - m[4] * (m[1] * m[10] - m[9] * m[2])
              + m[8] * (m[1] * m[ 6] - m[5] * m[2]);
    if(det == 0f) return null;
    det = 1f / det;

    r[ 0] =   det * (m[5] * m[10] - m[9] * m[6]);
    r[ 4] = - det * (m[4] * m[10] - m[8] * m[6]);
    r[ 8] =   det * (m[4] * m[ 9] - m[8] * m[5]);

    r[ 1] = - det * (m[1] * m[10] - m[9] * m[2]);
    r[ 5] =   det * (m[0] * m[10] - m[8] * m[2]);
    r[ 9] = - det * (m[0] * m[ 9] - m[8] * m[1]);

    r[ 2] =   det * (m[1] * m[ 6] - m[5] * m[2]);
    r[ 6] = - det * (m[0] * m[ 6] - m[4] * m[2]);
    r[10] =   det * (m[0] * m[ 5] - m[4] * m[1]);
    
    r[15] =   1f;
    return r;
  }


  /**
   * Multiply a 4*4 matrix by another, as if they were 3*3.
   * @param a the first / left matrix
   * @param b the second / right matrix
   * @return the result
   */
  public static final float[] matrixMultiply(float[] b, float[] a) {
    float[] r = new float[16];
    
    r[ 0] = a[ 0] * b[ 0] + a[ 1] * b[ 4] + a[ 2] * b[ 8];
    r[ 4] = a[ 4] * b[ 0] + a[ 5] * b[ 4] + a[ 6] * b[ 8];
    r[ 8] = a[ 8] * b[ 0] + a[ 9] * b[ 4] + a[10] * b[ 8];
    r[12] = a[12] * b[ 0] + a[13] * b[ 4] + a[14] * b[ 8] + b[12];
    
    r[ 1] = a[ 0] * b[ 1] + a[ 1] * b[ 5] + a[ 2] * b[ 9];
    r[ 5] = a[ 4] * b[ 1] + a[ 5] * b[ 5] + a[ 6] * b[ 9];
    r[ 9] = a[ 8] * b[ 1] + a[ 9] * b[ 5] + a[10] * b[ 9];
    r[13] = a[12] * b[ 1] + a[13] * b[ 5] + a[14] * b[ 9] + b[13];
    
    r[ 2] = a[ 0] * b[ 2] + a[ 1] * b[ 6] + a[ 2] * b[10];
    r[ 6] = a[ 4] * b[ 2] + a[ 5] * b[ 6] + a[ 6] * b[10];
    r[10] = a[ 8] * b[ 2] + a[ 9] * b[ 6] + a[10] * b[10];
    r[14] = a[12] * b[ 2] + a[13] * b[ 6] + a[14] * b[10] + b[14];
    
    r[ 3] = 0;
    r[ 7] = 0;
    r[11] = 0;
    r[15] = 1;

    return r;
  }
  /**
   * Multiply a 4*4 matrix by another.
   * @param a the first / left matrix
   * @param b the second / right matrix
   * @return the result
   */
  public static final float[] matrixMultiply_4(float[] b, float[] a) {
    float[] r = new float[16];
    
    r[ 0] = a[ 0] * b[ 0] + a[ 1] * b[ 4] + a[ 2] * b[ 8] + a[ 3] * b[12];
    r[ 4] = a[ 4] * b[ 0] + a[ 5] * b[ 4] + a[ 6] * b[ 8] + a[ 7] * b[12];
    r[ 8] = a[ 8] * b[ 0] + a[ 9] * b[ 4] + a[10] * b[ 8] + a[11] * b[12];
    r[12] = a[12] * b[ 0] + a[13] * b[ 4] + a[14] * b[ 8] + a[15] * b[12];
    
    r[ 1] = a[ 0] * b[ 1] + a[ 1] * b[ 5] + a[ 2] * b[ 9] + a[ 3] * b[13];
    r[ 5] = a[ 4] * b[ 1] + a[ 5] * b[ 5] + a[ 6] * b[ 9] + a[ 7] * b[13];
    r[ 9] = a[ 8] * b[ 1] + a[ 9] * b[ 5] + a[10] * b[ 9] + a[11] * b[13];
    r[13] = a[12] * b[ 1] + a[13] * b[ 5] + a[14] * b[ 9] + a[15] * b[13];
    
    r[ 2] = a[ 0] * b[ 2] + a[ 1] * b[ 6] + a[ 2] * b[10] + a[ 3] * b[14];
    r[ 6] = a[ 4] * b[ 2] + a[ 5] * b[ 6] + a[ 6] * b[10] + a[ 7] * b[14];
    r[10] = a[ 8] * b[ 2] + a[ 9] * b[ 6] + a[10] * b[10] + a[11] * b[14];
    r[14] = a[12] * b[ 2] + a[13] * b[ 6] + a[14] * b[10] + a[15] * b[14];
    
    r[ 3] = a[ 0] * b[ 3] + a[ 1] * b[ 7] + a[ 2] * b[11] + a[ 3] * b[15];
    r[ 7] = a[ 4] * b[ 3] + a[ 5] * b[ 7] + a[ 6] * b[11] + a[ 7] * b[15];
    r[11] = a[ 8] * b[ 3] + a[ 9] * b[ 7] + a[10] * b[11] + a[11] * b[15];
    r[15] = a[12] * b[ 3] + a[13] * b[ 7] + a[14] * b[11] + a[15] * b[15];

    return r;
  }
  
  /**
   * Multiply a point by a 4*4 matrix.
   * @param m the matrix
   * @param p the point
   * the resulting point
   */
  public static final float[] pointMultiplyByMatrix(float[] m, float[] p) { // Assume v[3] = 1.
    float[] r = { p[0] * m[0] + p[1] * m[4] + p[2] * m[ 8] + m[12],
                  p[0] * m[1] + p[1] * m[5] + p[2] * m[ 9] + m[13],
                  p[0] * m[2] + p[1] * m[6] + p[2] * m[10] + m[14]
    };
    return r;
  }
  /**
   * Multiply a vector by a 4*4 matrix.
   * @param m the matrix
   * @param v the vector
   * @return the resulting vector
   */
  public static final float[] vectorMultiplyByMatrix(float[] m, float[] v) {
    float[] r = { v[0] * m[0] + v[1] * m[4] + v[2] * m[ 8],
                  v[0] * m[1] + v[1] * m[5] + v[2] * m[ 9],
                  v[0] * m[2] + v[1] * m[6] + v[2] * m[10]
    };
    return r;
  }

  /**
   * Compare 2 matrix.
   * @param a the first matrix
   * @param b the second matrix
   * @return true if a and b are equal (or very near)
   */
  public static final boolean matrixEqual(float[] a, float[] b) {
    for(int i = 0; i < 16; i++) {
      if(Math.abs(a[i] - b[i]) > EPSILON) return false;
    }
    return true;
  }

  /**
   * Convert a matrix into a string. Useful for debuging soya.
   * @param m the matrix
   * @return the string
   */
  public static final String matrixToString(float[] m) {
    String s = "matrix 4_4 {\n";
    s = s + Float.toString(m[ 0]) + " " + Float.toString(m[ 4]) + " " + Float.toString(m[ 8]) + "\n";
    s = s + Float.toString(m[ 1]) + " " + Float.toString(m[ 5]) + " " + Float.toString(m[ 9]) + "\n";
    s = s + Float.toString(m[ 2]) + " " + Float.toString(m[ 6]) + " " + Float.toString(m[10]) + "\n";
    s = s + Float.toString(m[ 3]) + " " + Float.toString(m[ 7]) + " " + Float.toString(m[11]) + "\n";
    s = s + "X: " + Float.toString(m[12]) + " Y: " + Float.toString(m[13]) + " Z: " + Float.toString(m[14]) + " W: " + Float.toString(m[15]) + "\n";
    s = s + "}";
    return s;
  }

  /**
   * Create a new identity matrix.
   * @return an identity matrix
   */
  public static final float[] matrixIdentity() {
    float[] m = new float[16];
    matrixIdentity(m);
    return m;
  }

  /**
   * Set a matrix to identity matrix.
   * @param m the matrix
   */
  public static final void matrixIdentity(float[] m) {
    m[ 0] = 1f;
    m[ 1] = 0f;
    m[ 2] = 0f;
    m[ 3] = 0f;
    m[ 4] = 0f;
    m[ 5] = 1f;
    m[ 6] = 0f;
    m[ 7] = 0f;
    m[ 8] = 0f;
    m[ 9] = 0f;
    m[10] = 1f;
    m[11] = 0f;
    m[12] = 0f;
    m[13] = 0f;
    m[14] = 0f;
    m[15] = 1f;
  }

  /**
   * Create a scale matrix.
   * @param x the x factor of the scaling
   * @param y the y factor of the scaling 
   * @param z the z factor of the scaling
   * @return the matrix
   */
  public static float[] matrixScale(float x, float y, float z) {
    float[] m2 = { x,  0f, 0f, 0f,
                   0f, y,  0f, 0f,
                   0f, 0f, z,  0f,
                   0f, 0f, 0f, 1f };
    return m2;
  }
  /**
   * Scale a matrix (this is equivalent to OpenGL glScale* ).
   * @param m the matrix
   * @param x the x factor of the scaling
   * @param y the y factor of the scaling
   * @param z the z factor of the scaling
   * @return the scaled matrix
   */
  public static float[] matrixScale(float[] m, float x, float y, float z) {
    float r[] = new float[16];
    r[ 0] = x * m[ 0];
    r[ 4] = y * m[ 4];
    r[ 8] = z * m[ 8];
    r[12] = m[12];
    r[ 1] = x * m[ 1];
    r[ 5] = y * m[ 5];
    r[ 9] = z * m[ 9];
    r[13] = m[13];
    r[ 2] = x * m[ 2];
    r[ 6] = y * m[ 6];
    r[10] = z * m[10];
    r[14] = m[14];
    r[ 3] = 0;
    r[ 7] = 0;
    r[11] = 0;
    r[15] = 1;
    return r;
//    return matrixMultiply(m, matrixScale(x, y, z));
  }
  
  /**
   * Create a lateral rotation matrix (lateral rotation is around a (0, 1, 0) axis).
   * @param angle the angle of the rotation
   * @return the matrix
   */
  public static float[] matrixRotateLateral(float angle) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float[] m2 = { cos, 0f, -sin, 0f,
                   0f , 1f,  0f , 0f,
                   sin, 0f,  cos, 0f,
                   0f , 0f,  0f , 1f };
    return m2;
  }
  /**
   * Laterally rotate a matrix (lateral rotation is around a (0, 1, 0) axis).
   * @param angle the angle of the rotation
   * @param m the matrix to rotate
   * @return the resulting matrix
   */
  public static float[] matrixRotateLateral(float[] m, float angle) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float r[] = new float[16];
    r[ 0] = m[ 0] * cos + m[ 2] * sin;
    r[ 4] = m[ 4] * cos + m[ 6] * sin;
    r[ 8] = m[ 8] * cos + m[10] * sin;
    r[12] = m[12] * cos + m[14] * sin;
    r[ 1] = m[ 1];
    r[ 5] = m[ 5];
    r[ 9] = m[ 9];
    r[13] = m[13];
    r[ 2] = -m[ 0] * sin + m[ 2] * cos;
    r[ 6] = -m[ 4] * sin + m[ 6] * cos;
    r[10] = -m[ 8] * sin + m[10] * cos;
    r[14] = -m[12] * sin + m[14] * cos;
    r[ 3] = 0;
    r[ 7] = 0;
    r[11] = 0;
    r[15] = 1;
    return r;
//    return matrixMultiply(matrixRotateLateral(angle), m);
  }
  /**
   * Create a vertical rotation matrix (vertical rotation is around a (1, 0, 0) axis).
   * @param angle the angle of the rotation
   * @return the matrix
   */
  public static float[] matrixRotateVertical(float angle) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float[] m2 = { 1f,  0f , 0f , 0f,
                   0f,  cos, sin, 0f,
                   0f, -sin, cos, 0f,
                   0f,  0f , 0f , 1f };
    return m2;
  }
  /**
   * Vertically rotate a matrix (vertical rotation is around a (1, 0, 0) axis).
   * @param angle the angle of the rotation
   * @param m the matrix to rotate
   * @return the resulting matrix
   */
  public static float[] matrixRotateVertical(float[] m, float angle) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float r[] = new float[16];
    r[ 0] = m[ 0];
    r[ 4] = m[ 4];
    r[ 8] = m[ 8];
    r[12] = m[12];
    r[ 1] = m[ 1] * cos - m[ 2] * sin;
    r[ 5] = m[ 5] * cos - m[ 6] * sin;
    r[ 9] = m[ 9] * cos - m[10] * sin;
    r[13] = m[13] * cos - m[14] * sin;
    r[ 2] = m[ 1] * sin + m[ 2] * cos;
    r[ 6] = m[ 5] * sin + m[ 6] * cos;
    r[10] = m[ 9] * sin + m[10] * cos;
    r[14] = m[13] * sin + m[14] * cos;
    r[ 3] = 0;
    r[ 7] = 0;
    r[11] = 0;
    r[15] = 1;
    return r;
//    return matrixMultiply(matrixRotateVertical(angle), m);
  }
  /**
   * Create a incline-rotation matrix (incline-rotation is around a (0, 0, 1) axis).
   * @param angle the angle of the rotation
   * @return the matrix
   */
  public static float[] matrixRotateIncline(float angle) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float m2[] = { cos, sin, 0f, 0f,
                  -sin, cos, 0f, 0f,
                   0f , 0f , 1f, 0f,
                   0f , 0f , 0f, 1f };
    return m2;
  }
  /**
   * Incline a matrix (incline-rotation is around a (0, 0, 1) axis).
   * @param angle the angle of the rotation
   * @param m the matrix to rotate
   * @return the resulting matrix 
   */
  public static float[] matrixRotateIncline(float[] m, float angle) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float r[] = new float[16];
    r[ 0] = m[ 0] * cos - m[ 1] * sin;
    r[ 4] = m[ 4] * cos - m[ 5] * sin;
    r[ 8] = m[ 8] * cos - m[ 9] * sin;
    r[12] = m[12] * cos - m[13] * sin;
    r[ 1] = m[ 0] * sin + m[ 1] * cos;
    r[ 5] = m[ 4] * sin + m[ 5] * cos;
    r[ 9] = m[ 8] * sin + m[ 9] * cos;
    r[13] = m[12] * sin + m[13] * cos;
    r[ 2] = m[ 2];
    r[ 6] = m[ 6];
    r[10] = m[10];
    r[14] = m[14];
    r[ 3] = 0;
    r[ 7] = 0;
    r[11] = 0;
    r[15] = 1;
    return r;
//    return matrixMultiply(matrixRotateIncline(angle), m);
  }
  /**
   * Create a rotation matrix.
   * @param angle the angle of the rotation
   * @param x the x coordinate of the rotation axis
   * @param y the y coordinate of the rotation axis
   * @param z the z coordinate of the rotation axis
   * @return the matrix
   */
  public static float[] matrixRotate(float angle, float x, float y, float z) {
    if(angle == 0f) return matrixIdentity();
    angle = (float) Math.toRadians(angle);
    float d = (float) java.lang.Math.sqrt(java.lang.Math.pow(x, 2) + java.lang.Math.pow(y, 2) + java.lang.Math.pow(z, 2));
    if(d != 1f) {
      x = x / d;
      y = y / d;
      z = z / d;
    }
    float cos = (float) java.lang.Math.cos(angle);
    float sin = (float) java.lang.Math.sin(angle);
    float co1 = 1f - cos;
    float m2[] = { x * x * co1 + cos    ,  y * x * co1 + z * sin, z * x * co1 - y * sin, 0f,
                   x * y * co1 - z * sin,  y * y * co1 + cos    , z * y * co1 + x * sin, 0f,
                   x * z * co1 + y * sin,  y * z * co1 - x * sin, z * z * co1 + cos    , 0f,
                   0f                   ,  0f                   , 0f                   , 1f };
    return m2;
  }
  /**
   * Rotate a matrix (this is equivalent to OpenGL glRotate*).
   * @param m the matrix to rotate
   * @param angle the angle of the rotation
   * @param x the x coordinate of the rotation axis
   * @param y the y coordinate of the rotation axis
   * @param z the z coordinate of the rotation axis
   * @return the resulting matrix
   */
  public static float[] matrixRotate(float[] m, float angle, float x, float y, float z) {
    return matrixMultiply(matrixRotate(angle, x, y, z), m);
  }

  /**
   *  Rotation  about an arbitrary Axis
   *  @param alpha the angle of the rotation
   *  @param p1 first axis point
   *  @param p2 second axis point
   *  @return the rotation matrix
   */
  public static float[] matrixRotate(float alpha, float[] p1, float[] p2){
    alpha = alpha * PI / 180f;
    
    float a1 = p1[0];
    float a2 = p1[1];
    float a3 = p1[2];
      
    //Compute the vector defines by point p1 and p2
    float v1 = p2[0] - a1 ;
    float v2 = p2[1] - a2 ;
    float v3 = p2[2] - a3 ;
        
    double theta = Math.atan2(v2, v1);
    double phi = Math.atan2(Math.sqrt(v1 * v1 + v2 * v2), v3);
    
    float cosAlpha, sinAlpha, sinPhi2; 
    float cosTheta, sinTheta, cosPhi2;
    float cosPhi, sinPhi, cosTheta2, sinTheta2 ; 
    
    cosPhi = (float) Math.cos(phi); cosTheta = (float) Math.cos(theta) ; cosTheta2 = (float) cosTheta * cosTheta ;
    sinPhi = (float) Math.sin(phi); sinTheta = (float) Math.sin(theta) ; sinTheta2 = (float) sinTheta * sinTheta ; 
  
    sinPhi2 = (float) sinPhi*sinPhi ;
    cosPhi2 = (float) cosPhi*cosPhi ;
    
    cosAlpha = (float) Math.cos(alpha) ;
    sinAlpha = (float) Math.sin(alpha) ;
    
    float c = (float) 1.0 - cosAlpha ; 
    
    float r11,r12,r13,r14,r21,r22,r23,r24,r31,r32,r33,r34;
    r11 =  cosTheta2 * ( cosAlpha * cosPhi2 +sinPhi2 ) + cosAlpha * sinTheta2 ;
    r12 = sinAlpha * cosPhi + c * sinPhi2 * cosTheta * sinTheta ; 
    r13 = sinPhi * (cosPhi * cosTheta * c - sinAlpha*sinTheta) ; 
    
    r21 = sinPhi2 * cosTheta * sinTheta*c - sinAlpha*cosPhi ; 
    r22 = sinTheta2 * (cosAlpha*cosPhi2 +sinPhi2) + cosAlpha*cosTheta2 ;
    r23 = sinPhi * (cosPhi*sinTheta*c + sinAlpha*cosTheta);
    
    r31 = sinPhi * (cosPhi*cosTheta*c + sinAlpha*sinTheta);
    r32 = sinPhi * (cosPhi*sinTheta*c - sinAlpha*cosTheta);
    r33 =  cosAlpha * sinPhi2 + cosPhi2 ;
    
    r14 = a1 - a1*r11 - a2*r21 - a3*r31 ;
    r24 = a2 - a1*r12 - a2*r22 - a3*r32 ;
    r34 = a3 - a1*r13 - a2*r23 - a3*r33 ;
    
    float[] m2 = { r11 , r12 , r13 , 0f,
                   r21 , r22 , r23 , 0f,
                   r31 , r32 , r33 , 0f,
                   r14 , r24 , r34 , 1f
    };  
    return m2;
  }
  /**
   *  Rotation  about an arbitrary Axis
   *  @param m the matrix to rotate
   *  @param alpha the angle of the rotation
   *  @param p1 first axis point
   *  @param p2 second axis point
   *  @return the rotated matrix
   */
  public static float[] matrixRotate(float[] m, float alpha, float[] p1, float[] p2) {
    return matrixMultiply(matrixRotate(alpha, p1, p2), m);
  }
  
  /**
   * Create a translation matrix.
   * @param x the x coordinate of the translation vector
   * @param y the y coordinate of the translation vector
   * @param z the z coordinate of the translation vector
   * @return the translation matrix
   */
  public static float[] matrixTranslate(float x, float y, float z) {
    float m2[] = { 1f, 0f, 0f, 0f,
                   0f, 1f, 0f, 0f,
                   0f, 0f, 1f, 0f,
                   x , y , z , 1f };
    return m2;
  }
  /**
   * Translate a matrix (this is equivalent to OpenGL glTranslate*).
   * @param m the matrix to translate
   * @param x the x coordinate of the translation vector
   * @param y the y coordinate of the translation vector
   * @param z the z coordinate of the translation vector
   * @return the resulting matrix
   */
  public static float[] matrixTranslate(float[] m, float x, float y, float z) {
    float[] r = new float[16];
    System.arraycopy(m, 0, r, 0, 12);
    r[12] = m[12] + x;
    r[13] = m[13] + y;
    r[14] = m[14] + z;
    r[15] = 1f;
    return r;
    //return matrixMultiply(matrixTranslate(x, y, z), m);
  }

  public static float[] matrixPerspective(float fovy, float aspect, float znear, float zfar) {
    // this code is adapted from Mesa :)
    float xmax, ymax;
    ymax = znear * (float) Math.tan(Math.toRadians(fovy / 2f));
    xmax = aspect * ymax;
    return matrixFrustum(-xmax, xmax, -ymax, ymax, znear, zfar);
  }

  public static float[] matrixFrustum(float left, float right, float bottom, float top, float near, float far) {
    // this code is adapted from Mesa :)
    float x, y, a, b, c, d;
    float[] r = new float[16];
    r[14] = right - left;
    r[10] = top - bottom;
    r[0 ] = 2f * near;
    r[5 ] = r[0] / r[10];
    r[0 ] = r[0] / r[14];
    r[8 ] = (right + left) / r[14];
    r[9 ] = (top + bottom) / r[10];
    r[14] = far - near;
    r[10] = -(far + near) / r[14];
    r[14] = -(2f * far * near) / r[14];  // error ? (this rem was in Mesa)
    r[1 ] = 0f;
    r[2 ] = 0f;
    r[3 ] = 0f;
    r[4 ] = 0f;
    r[6 ] = 0f;
    r[7 ] = 0f;
    r[11] = -1f;
    r[12] = 0f;
    r[13] = 0f;
    r[15] = 0f;
    return r;
  }
}

   
    
    
    
    
    
    
  








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4.Find exponential value of a number using Math.exp
5.Find floor value of a number using Math.floor
6.Find minimum of two numbers using Math.min
7.Find power using Math.pow
8.Find square root of a number using Math.sqrt
9.Find natural logarithm value of a number using Math.log
10.Find maximum of two numbers using Math.max
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17.Min Demo
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20.Conversion between polar and rectangular coordinates
21.Using the pow() function
22.Using strict math at the method level
23.Calculating hyperbolic functions
24.Calculating trigonometric functions
25.Weighted floating-point comparisons
26.Solving right triangles
27.Applying the quadratic formula
28.Calculate the floor of the log, base 2
29.Greatest Common Divisor (GCD) of positive integer numbers
30.Least Common Multiple (LCM) of two strictly positive integer numbers
31.Moving Average
32.Make Exponention
33.Caclulate the factorial of N
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35.Complex Number Demo
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38.Returns an integer hash code representing the given double value.
39.Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n as a double.
40.Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n.
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42.For a double precision value x, this method returns +1.0 if x >= 0 and -1.0 if x < 0. Returns NaN if x is NaN.
43.For a float value x, this method returns +1.0F if x >= 0 and -1.0F if x < 0. Returns NaN if x is NaN.
44.Normalize an angle in a 2&pi wide interval around a center value.
45.Normalizes an angle to a relative angle.
46.Normalizes an angle to an absolute angle
47.Normalizes an angle to be near an absolute angle
48.Returns the natural logarithm of n!.
49.Returns the least common multiple between two integer values.
50.Gets the greatest common divisor of the absolute value of two numbers
51.Matrix manipulation
52.Returns exact (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient
53.Returns a double representation of the (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient
54.Returns the natural log of the (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient
55.Returns the hyperbolic cosine of x.
56.Math Utils
57.Implements the methods which are in the standard J2SE's Math class, but are not in in J2ME's.
58.Utility methods for mathematical problems.
59.A math utility class with static methods.
60.Computes the binomial coefficient "n over k"
61.Log Gamma
62.Log Beta
63.Beta
64.Gamma
65.Factorial
66.Computes p(x;n,p) where x~B(n,p)
67.Returns the sum of two doubles expressed in log space
68.sigmod
69.sigmod rev
70.Numbers that are closer than this are considered equal
71.Returns the KL divergence, K(p1 || p2).
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73.Returns the difference of two doubles expressed in log space
74.Is Prime
75.Statistical functions on arrays of numbers, namely, the mean, variance, standard deviation, covariance, min and max
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79.Population Standard Deviation
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