/* Copyright (c) 2013, Brandon Jones, Colin MacKenzie IV. All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

  * Redistributions of source code must retain the above copyright notice, this
    list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above copyright notice,
    this list of conditions and the following disclaimer in the documentation 
    and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */

/**
 * @class 4x4 Matrix
 * @name mat4
 */
var mat4 = {};

/**
 * Creates a new identity mat4
 *
 * @returns {mat4} a new 4x4 matrix
 */
mat4.create = function() {
    var out = new GLMAT_ARRAY_TYPE(16);
    out[0] = 1;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 0;
    out[5] = 1;
    out[6] = 0;
    out[7] = 0;
    out[8] = 0;
    out[9] = 0;
    out[10] = 1;
    out[11] = 0;
    out[12] = 0;
    out[13] = 0;
    out[14] = 0;
    out[15] = 1;
    return out;
};

/**
 * Creates a new mat4 initialized with values from an existing matrix
 *
 * @param {mat4} a matrix to clone
 * @returns {mat4} a new 4x4 matrix
 */
mat4.clone = function(a) {
    var out = new GLMAT_ARRAY_TYPE(16);
    out[0] = a[0];
    out[1] = a[1];
    out[2] = a[2];
    out[3] = a[3];
    out[4] = a[4];
    out[5] = a[5];
    out[6] = a[6];
    out[7] = a[7];
    out[8] = a[8];
    out[9] = a[9];
    out[10] = a[10];
    out[11] = a[11];
    out[12] = a[12];
    out[13] = a[13];
    out[14] = a[14];
    out[15] = a[15];
    return out;
};

/**
 * Copy the values from one mat4 to another
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the source matrix
 * @returns {mat4} out
 */
mat4.copy = function(out, a) {
    out[0] = a[0];
    out[1] = a[1];
    out[2] = a[2];
    out[3] = a[3];
    out[4] = a[4];
    out[5] = a[5];
    out[6] = a[6];
    out[7] = a[7];
    out[8] = a[8];
    out[9] = a[9];
    out[10] = a[10];
    out[11] = a[11];
    out[12] = a[12];
    out[13] = a[13];
    out[14] = a[14];
    out[15] = a[15];
    return out;
};

/**
 * Set a mat4 to the identity matrix
 *
 * @param {mat4} out the receiving matrix
 * @returns {mat4} out
 */
mat4.identity = function(out) {
    out[0] = 1;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 0;
    out[5] = 1;
    out[6] = 0;
    out[7] = 0;
    out[8] = 0;
    out[9] = 0;
    out[10] = 1;
    out[11] = 0;
    out[12] = 0;
    out[13] = 0;
    out[14] = 0;
    out[15] = 1;
    return out;
};

/**
 * Transpose the values of a mat4
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the source matrix
 * @returns {mat4} out
 */
mat4.transpose = function(out, a) {
    // If we are transposing ourselves we can skip a few steps but have to cache some values
    if (out === a) {
        var a01 = a[1], a02 = a[2], a03 = a[3],
            a12 = a[6], a13 = a[7],
            a23 = a[11];

        out[1] = a[4];
        out[2] = a[8];
        out[3] = a[12];
        out[4] = a01;
        out[6] = a[9];
        out[7] = a[13];
        out[8] = a02;
        out[9] = a12;
        out[11] = a[14];
        out[12] = a03;
        out[13] = a13;
        out[14] = a23;
    } else {
        out[0] = a[0];
        out[1] = a[4];
        out[2] = a[8];
        out[3] = a[12];
        out[4] = a[1];
        out[5] = a[5];
        out[6] = a[9];
        out[7] = a[13];
        out[8] = a[2];
        out[9] = a[6];
        out[10] = a[10];
        out[11] = a[14];
        out[12] = a[3];
        out[13] = a[7];
        out[14] = a[11];
        out[15] = a[15];
    }
    
    return out;
};

/**
 * Inverts a mat4
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the source matrix
 * @returns {mat4} out
 */
mat4.invert = function(out, a) {
    var a00 = a[0], a01 = a[1], a02 = a[2], a03 = a[3],
        a10 = a[4], a11 = a[5], a12 = a[6], a13 = a[7],
        a20 = a[8], a21 = a[9], a22 = a[10], a23 = a[11],
        a30 = a[12], a31 = a[13], a32 = a[14], a33 = a[15],

        b00 = a00 * a11 - a01 * a10,
        b01 = a00 * a12 - a02 * a10,
        b02 = a00 * a13 - a03 * a10,
        b03 = a01 * a12 - a02 * a11,
        b04 = a01 * a13 - a03 * a11,
        b05 = a02 * a13 - a03 * a12,
        b06 = a20 * a31 - a21 * a30,
        b07 = a20 * a32 - a22 * a30,
        b08 = a20 * a33 - a23 * a30,
        b09 = a21 * a32 - a22 * a31,
        b10 = a21 * a33 - a23 * a31,
        b11 = a22 * a33 - a23 * a32,

        // Calculate the determinant
        det = b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;

    if (!det) { 
        return null; 
    }
    det = 1.0 / det;

    out[0] = (a11 * b11 - a12 * b10 + a13 * b09) * det;
    out[1] = (a02 * b10 - a01 * b11 - a03 * b09) * det;
    out[2] = (a31 * b05 - a32 * b04 + a33 * b03) * det;
    out[3] = (a22 * b04 - a21 * b05 - a23 * b03) * det;
    out[4] = (a12 * b08 - a10 * b11 - a13 * b07) * det;
    out[5] = (a00 * b11 - a02 * b08 + a03 * b07) * det;
    out[6] = (a32 * b02 - a30 * b05 - a33 * b01) * det;
    out[7] = (a20 * b05 - a22 * b02 + a23 * b01) * det;
    out[8] = (a10 * b10 - a11 * b08 + a13 * b06) * det;
    out[9] = (a01 * b08 - a00 * b10 - a03 * b06) * det;
    out[10] = (a30 * b04 - a31 * b02 + a33 * b00) * det;
    out[11] = (a21 * b02 - a20 * b04 - a23 * b00) * det;
    out[12] = (a11 * b07 - a10 * b09 - a12 * b06) * det;
    out[13] = (a00 * b09 - a01 * b07 + a02 * b06) * det;
    out[14] = (a31 * b01 - a30 * b03 - a32 * b00) * det;
    out[15] = (a20 * b03 - a21 * b01 + a22 * b00) * det;

    return out;
};

/**
 * Calculates the adjugate of a mat4
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the source matrix
 * @returns {mat4} out
 */
mat4.adjoint = function(out, a) {
    var a00 = a[0], a01 = a[1], a02 = a[2], a03 = a[3],
        a10 = a[4], a11 = a[5], a12 = a[6], a13 = a[7],
        a20 = a[8], a21 = a[9], a22 = a[10], a23 = a[11],
        a30 = a[12], a31 = a[13], a32 = a[14], a33 = a[15];

    out[0]  =  (a11 * (a22 * a33 - a23 * a32) - a21 * (a12 * a33 - a13 * a32) + a31 * (a12 * a23 - a13 * a22));
    out[1]  = -(a01 * (a22 * a33 - a23 * a32) - a21 * (a02 * a33 - a03 * a32) + a31 * (a02 * a23 - a03 * a22));
    out[2]  =  (a01 * (a12 * a33 - a13 * a32) - a11 * (a02 * a33 - a03 * a32) + a31 * (a02 * a13 - a03 * a12));
    out[3]  = -(a01 * (a12 * a23 - a13 * a22) - a11 * (a02 * a23 - a03 * a22) + a21 * (a02 * a13 - a03 * a12));
    out[4]  = -(a10 * (a22 * a33 - a23 * a32) - a20 * (a12 * a33 - a13 * a32) + a30 * (a12 * a23 - a13 * a22));
    out[5]  =  (a00 * (a22 * a33 - a23 * a32) - a20 * (a02 * a33 - a03 * a32) + a30 * (a02 * a23 - a03 * a22));
    out[6]  = -(a00 * (a12 * a33 - a13 * a32) - a10 * (a02 * a33 - a03 * a32) + a30 * (a02 * a13 - a03 * a12));
    out[7]  =  (a00 * (a12 * a23 - a13 * a22) - a10 * (a02 * a23 - a03 * a22) + a20 * (a02 * a13 - a03 * a12));
    out[8]  =  (a10 * (a21 * a33 - a23 * a31) - a20 * (a11 * a33 - a13 * a31) + a30 * (a11 * a23 - a13 * a21));
    out[9]  = -(a00 * (a21 * a33 - a23 * a31) - a20 * (a01 * a33 - a03 * a31) + a30 * (a01 * a23 - a03 * a21));
    out[10] =  (a00 * (a11 * a33 - a13 * a31) - a10 * (a01 * a33 - a03 * a31) + a30 * (a01 * a13 - a03 * a11));
    out[11] = -(a00 * (a11 * a23 - a13 * a21) - a10 * (a01 * a23 - a03 * a21) + a20 * (a01 * a13 - a03 * a11));
    out[12] = -(a10 * (a21 * a32 - a22 * a31) - a20 * (a11 * a32 - a12 * a31) + a30 * (a11 * a22 - a12 * a21));
    out[13] =  (a00 * (a21 * a32 - a22 * a31) - a20 * (a01 * a32 - a02 * a31) + a30 * (a01 * a22 - a02 * a21));
    out[14] = -(a00 * (a11 * a32 - a12 * a31) - a10 * (a01 * a32 - a02 * a31) + a30 * (a01 * a12 - a02 * a11));
    out[15] =  (a00 * (a11 * a22 - a12 * a21) - a10 * (a01 * a22 - a02 * a21) + a20 * (a01 * a12 - a02 * a11));
    return out;
};

/**
 * Calculates the determinant of a mat4
 *
 * @param {mat4} a the source matrix
 * @returns {Number} determinant of a
 */
mat4.determinant = function (a) {
    var a00 = a[0], a01 = a[1], a02 = a[2], a03 = a[3],
        a10 = a[4], a11 = a[5], a12 = a[6], a13 = a[7],
        a20 = a[8], a21 = a[9], a22 = a[10], a23 = a[11],
        a30 = a[12], a31 = a[13], a32 = a[14], a33 = a[15],

        b00 = a00 * a11 - a01 * a10,
        b01 = a00 * a12 - a02 * a10,
        b02 = a00 * a13 - a03 * a10,
        b03 = a01 * a12 - a02 * a11,
        b04 = a01 * a13 - a03 * a11,
        b05 = a02 * a13 - a03 * a12,
        b06 = a20 * a31 - a21 * a30,
        b07 = a20 * a32 - a22 * a30,
        b08 = a20 * a33 - a23 * a30,
        b09 = a21 * a32 - a22 * a31,
        b10 = a21 * a33 - a23 * a31,
        b11 = a22 * a33 - a23 * a32;

    // Calculate the determinant
    return b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;
};

/**
 * Multiplies two mat4's
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the first operand
 * @param {mat4} b the second operand
 * @returns {mat4} out
 */
mat4.multiply = function (out, a, b) {
    var a00 = a[0], a01 = a[1], a02 = a[2], a03 = a[3],
        a10 = a[4], a11 = a[5], a12 = a[6], a13 = a[7],
        a20 = a[8], a21 = a[9], a22 = a[10], a23 = a[11],
        a30 = a[12], a31 = a[13], a32 = a[14], a33 = a[15];

    // Cache only the current line of the second matrix
    var b0  = b[0], b1 = b[1], b2 = b[2], b3 = b[3];  
    out[0] = b0*a00 + b1*a10 + b2*a20 + b3*a30;
    out[1] = b0*a01 + b1*a11 + b2*a21 + b3*a31;
    out[2] = b0*a02 + b1*a12 + b2*a22 + b3*a32;
    out[3] = b0*a03 + b1*a13 + b2*a23 + b3*a33;

    b0 = b[4]; b1 = b[5]; b2 = b[6]; b3 = b[7];
    out[4] = b0*a00 + b1*a10 + b2*a20 + b3*a30;
    out[5] = b0*a01 + b1*a11 + b2*a21 + b3*a31;
    out[6] = b0*a02 + b1*a12 + b2*a22 + b3*a32;
    out[7] = b0*a03 + b1*a13 + b2*a23 + b3*a33;

    b0 = b[8]; b1 = b[9]; b2 = b[10]; b3 = b[11];
    out[8] = b0*a00 + b1*a10 + b2*a20 + b3*a30;
    out[9] = b0*a01 + b1*a11 + b2*a21 + b3*a31;
    out[10] = b0*a02 + b1*a12 + b2*a22 + b3*a32;
    out[11] = b0*a03 + b1*a13 + b2*a23 + b3*a33;

    b0 = b[12]; b1 = b[13]; b2 = b[14]; b3 = b[15];
    out[12] = b0*a00 + b1*a10 + b2*a20 + b3*a30;
    out[13] = b0*a01 + b1*a11 + b2*a21 + b3*a31;
    out[14] = b0*a02 + b1*a12 + b2*a22 + b3*a32;
    out[15] = b0*a03 + b1*a13 + b2*a23 + b3*a33;
    return out;
};

/**
 * Alias for {@link mat4.multiply}
 * @function
 */
mat4.mul = mat4.multiply;

/**
 * Translate a mat4 by the given vector
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the matrix to translate
 * @param {vec3} v vector to translate by
 * @returns {mat4} out
 */
mat4.translate = function (out, a, v) {
    var x = v[0], y = v[1], z = v[2],
        a00, a01, a02, a03,
        a10, a11, a12, a13,
        a20, a21, a22, a23;

    if (a === out) {
        out[12] = a[0] * x + a[4] * y + a[8] * z + a[12];
        out[13] = a[1] * x + a[5] * y + a[9] * z + a[13];
        out[14] = a[2] * x + a[6] * y + a[10] * z + a[14];
        out[15] = a[3] * x + a[7] * y + a[11] * z + a[15];
    } else {
        a00 = a[0]; a01 = a[1]; a02 = a[2]; a03 = a[3];
        a10 = a[4]; a11 = a[5]; a12 = a[6]; a13 = a[7];
        a20 = a[8]; a21 = a[9]; a22 = a[10]; a23 = a[11];

        out[0] = a00; out[1] = a01; out[2] = a02; out[3] = a03;
        out[4] = a10; out[5] = a11; out[6] = a12; out[7] = a13;
        out[8] = a20; out[9] = a21; out[10] = a22; out[11] = a23;

        out[12] = a00 * x + a10 * y + a20 * z + a[12];
        out[13] = a01 * x + a11 * y + a21 * z + a[13];
        out[14] = a02 * x + a12 * y + a22 * z + a[14];
        out[15] = a03 * x + a13 * y + a23 * z + a[15];
    }

    return out;
};

/**
 * Scales the mat4 by the dimensions in the given vec3
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the matrix to scale
 * @param {vec3} v the vec3 to scale the matrix by
 * @returns {mat4} out
 **/
mat4.scale = function(out, a, v) {
    var x = v[0], y = v[1], z = v[2];

    out[0] = a[0] * x;
    out[1] = a[1] * x;
    out[2] = a[2] * x;
    out[3] = a[3] * x;
    out[4] = a[4] * y;
    out[5] = a[5] * y;
    out[6] = a[6] * y;
    out[7] = a[7] * y;
    out[8] = a[8] * z;
    out[9] = a[9] * z;
    out[10] = a[10] * z;
    out[11] = a[11] * z;
    out[12] = a[12];
    out[13] = a[13];
    out[14] = a[14];
    out[15] = a[15];
    return out;
};

/**
 * Rotates a mat4 by the given angle
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the matrix to rotate
 * @param {Number} rad the angle to rotate the matrix by
 * @param {vec3} axis the axis to rotate around
 * @returns {mat4} out
 */
mat4.rotate = function (out, a, rad, axis) {
    var x = axis[0], y = axis[1], z = axis[2],
        len = Math.sqrt(x * x + y * y + z * z),
        s, c, t,
        a00, a01, a02, a03,
        a10, a11, a12, a13,
        a20, a21, a22, a23,
        b00, b01, b02,
        b10, b11, b12,
        b20, b21, b22;

    if (Math.abs(len) < GLMAT_EPSILON) { return null; }
    
    len = 1 / len;
    x *= len;
    y *= len;
    z *= len;

    s = Math.sin(rad);
    c = Math.cos(rad);
    t = 1 - c;

    a00 = a[0]; a01 = a[1]; a02 = a[2]; a03 = a[3];
    a10 = a[4]; a11 = a[5]; a12 = a[6]; a13 = a[7];
    a20 = a[8]; a21 = a[9]; a22 = a[10]; a23 = a[11];

    // Construct the elements of the rotation matrix
    b00 = x * x * t + c; b01 = y * x * t + z * s; b02 = z * x * t - y * s;
    b10 = x * y * t - z * s; b11 = y * y * t + c; b12 = z * y * t + x * s;
    b20 = x * z * t + y * s; b21 = y * z * t - x * s; b22 = z * z * t + c;

    // Perform rotation-specific matrix multiplication
    out[0] = a00 * b00 + a10 * b01 + a20 * b02;
    out[1] = a01 * b00 + a11 * b01 + a21 * b02;
    out[2] = a02 * b00 + a12 * b01 + a22 * b02;
    out[3] = a03 * b00 + a13 * b01 + a23 * b02;
    out[4] = a00 * b10 + a10 * b11 + a20 * b12;
    out[5] = a01 * b10 + a11 * b11 + a21 * b12;
    out[6] = a02 * b10 + a12 * b11 + a22 * b12;
    out[7] = a03 * b10 + a13 * b11 + a23 * b12;
    out[8] = a00 * b20 + a10 * b21 + a20 * b22;
    out[9] = a01 * b20 + a11 * b21 + a21 * b22;
    out[10] = a02 * b20 + a12 * b21 + a22 * b22;
    out[11] = a03 * b20 + a13 * b21 + a23 * b22;

    if (a !== out) { // If the source and destination differ, copy the unchanged last row
        out[12] = a[12];
        out[13] = a[13];
        out[14] = a[14];
        out[15] = a[15];
    }
    return out;
};

/**
 * Rotates a matrix by the given angle around the X axis
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the matrix to rotate
 * @param {Number} rad the angle to rotate the matrix by
 * @returns {mat4} out
 */
mat4.rotateX = function (out, a, rad) {
    var s = Math.sin(rad),
        c = Math.cos(rad),
        a10 = a[4],
        a11 = a[5],
        a12 = a[6],
        a13 = a[7],
        a20 = a[8],
        a21 = a[9],
        a22 = a[10],
        a23 = a[11];

    if (a !== out) { // If the source and destination differ, copy the unchanged rows
        out[0]  = a[0];
        out[1]  = a[1];
        out[2]  = a[2];
        out[3]  = a[3];
        out[12] = a[12];
        out[13] = a[13];
        out[14] = a[14];
        out[15] = a[15];
    }

    // Perform axis-specific matrix multiplication
    out[4] = a10 * c + a20 * s;
    out[5] = a11 * c + a21 * s;
    out[6] = a12 * c + a22 * s;
    out[7] = a13 * c + a23 * s;
    out[8] = a20 * c - a10 * s;
    out[9] = a21 * c - a11 * s;
    out[10] = a22 * c - a12 * s;
    out[11] = a23 * c - a13 * s;
    return out;
};

/**
 * Rotates a matrix by the given angle around the Y axis
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the matrix to rotate
 * @param {Number} rad the angle to rotate the matrix by
 * @returns {mat4} out
 */
mat4.rotateY = function (out, a, rad) {
    var s = Math.sin(rad),
        c = Math.cos(rad),
        a00 = a[0],
        a01 = a[1],
        a02 = a[2],
        a03 = a[3],
        a20 = a[8],
        a21 = a[9],
        a22 = a[10],
        a23 = a[11];

    if (a !== out) { // If the source and destination differ, copy the unchanged rows
        out[4]  = a[4];
        out[5]  = a[5];
        out[6]  = a[6];
        out[7]  = a[7];
        out[12] = a[12];
        out[13] = a[13];
        out[14] = a[14];
        out[15] = a[15];
    }

    // Perform axis-specific matrix multiplication
    out[0] = a00 * c - a20 * s;
    out[1] = a01 * c - a21 * s;
    out[2] = a02 * c - a22 * s;
    out[3] = a03 * c - a23 * s;
    out[8] = a00 * s + a20 * c;
    out[9] = a01 * s + a21 * c;
    out[10] = a02 * s + a22 * c;
    out[11] = a03 * s + a23 * c;
    return out;
};

/**
 * Rotates a matrix by the given angle around the Z axis
 *
 * @param {mat4} out the receiving matrix
 * @param {mat4} a the matrix to rotate
 * @param {Number} rad the angle to rotate the matrix by
 * @returns {mat4} out
 */
mat4.rotateZ = function (out, a, rad) {
    var s = Math.sin(rad),
        c = Math.cos(rad),
        a00 = a[0],
        a01 = a[1],
        a02 = a[2],
        a03 = a[3],
        a10 = a[4],
        a11 = a[5],
        a12 = a[6],
        a13 = a[7];

    if (a !== out) { // If the source and destination differ, copy the unchanged last row
        out[8]  = a[8];
        out[9]  = a[9];
        out[10] = a[10];
        out[11] = a[11];
        out[12] = a[12];
        out[13] = a[13];
        out[14] = a[14];
        out[15] = a[15];
    }

    // Perform axis-specific matrix multiplication
    out[0] = a00 * c + a10 * s;
    out[1] = a01 * c + a11 * s;
    out[2] = a02 * c + a12 * s;
    out[3] = a03 * c + a13 * s;
    out[4] = a10 * c - a00 * s;
    out[5] = a11 * c - a01 * s;
    out[6] = a12 * c - a02 * s;
    out[7] = a13 * c - a03 * s;
    return out;
};

/**
 * Creates a matrix from a quaternion rotation and vector translation
 * This is equivalent to (but much faster than):
 *
 *     mat4.identity(dest);
 *     mat4.translate(dest, vec);
 *     var quatMat = mat4.create();
 *     quat4.toMat4(quat, quatMat);
 *     mat4.multiply(dest, quatMat);
 *
 * @param {mat4} out mat4 receiving operation result
 * @param {quat4} q Rotation quaternion
 * @param {vec3} v Translation vector
 * @returns {mat4} out
 */
mat4.fromRotationTranslation = function (out, q, v) {
    // Quaternion math
    var x = q[0], y = q[1], z = q[2], w = q[3],
        x2 = x + x,
        y2 = y + y,
        z2 = z + z,

        xx = x * x2,
        xy = x * y2,
        xz = x * z2,
        yy = y * y2,
        yz = y * z2,
        zz = z * z2,
        wx = w * x2,
        wy = w * y2,
        wz = w * z2;

    out[0] = 1 - (yy + zz);
    out[1] = xy + wz;
    out[2] = xz - wy;
    out[3] = 0;
    out[4] = xy - wz;
    out[5] = 1 - (xx + zz);
    out[6] = yz + wx;
    out[7] = 0;
    out[8] = xz + wy;
    out[9] = yz - wx;
    out[10] = 1 - (xx + yy);
    out[11] = 0;
    out[12] = v[0];
    out[13] = v[1];
    out[14] = v[2];
    out[15] = 1;
    
    return out;
};

/**
* Calculates a 4x4 matrix from the given quaternion
*
* @param {mat4} out mat4 receiving operation result
* @param {quat} q Quaternion to create matrix from
*
* @returns {mat4} out
*/
mat4.fromQuat = function (out, q) {
    var x = q[0], y = q[1], z = q[2], w = q[3],
        x2 = x + x,
        y2 = y + y,
        z2 = z + z,

        xx = x * x2,
        xy = x * y2,
        xz = x * z2,
        yy = y * y2,
        yz = y * z2,
        zz = z * z2,
        wx = w * x2,
        wy = w * y2,
        wz = w * z2;

    out[0] = 1 - (yy + zz);
    out[1] = xy + wz;
    out[2] = xz - wy;
    out[3] = 0;

    out[4] = xy - wz;
    out[5] = 1 - (xx + zz);
    out[6] = yz + wx;
    out[7] = 0;

    out[8] = xz + wy;
    out[9] = yz - wx;
    out[10] = 1 - (xx + yy);
    out[11] = 0;

    out[12] = 0;
    out[13] = 0;
    out[14] = 0;
    out[15] = 1;

    return out;
};

/**
 * Generates a frustum matrix with the given bounds
 *
 * @param {mat4} out mat4 frustum matrix will be written into
 * @param {Number} left Left bound of the frustum
 * @param {Number} right Right bound of the frustum
 * @param {Number} bottom Bottom bound of the frustum
 * @param {Number} top Top bound of the frustum
 * @param {Number} near Near bound of the frustum
 * @param {Number} far Far bound of the frustum
 * @returns {mat4} out
 */
mat4.frustum = function (out, left, right, bottom, top, near, far) {
    var rl = 1 / (right - left),
        tb = 1 / (top - bottom),
        nf = 1 / (near - far);
    out[0] = (near * 2) * rl;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 0;
    out[5] = (near * 2) * tb;
    out[6] = 0;
    out[7] = 0;
    out[8] = (right + left) * rl;
    out[9] = (top + bottom) * tb;
    out[10] = (far + near) * nf;
    out[11] = -1;
    out[12] = 0;
    out[13] = 0;
    out[14] = (far * near * 2) * nf;
    out[15] = 0;
    return out;
};

/**
 * Generates a perspective projection matrix with the given bounds
 *
 * @param {mat4} out mat4 frustum matrix will be written into
 * @param {number} fovy Vertical field of view in radians
 * @param {number} aspect Aspect ratio. typically viewport width/height
 * @param {number} near Near bound of the frustum
 * @param {number} far Far bound of the frustum
 * @returns {mat4} out
 */
mat4.perspective = function (out, fovy, aspect, near, far) {
    var f = 1.0 / Math.tan(fovy / 2),
        nf = 1 / (near - far);
    out[0] = f / aspect;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 0;
    out[5] = f;
    out[6] = 0;
    out[7] = 0;
    out[8] = 0;
    out[9] = 0;
    out[10] = (far + near) * nf;
    out[11] = -1;
    out[12] = 0;
    out[13] = 0;
    out[14] = (2 * far * near) * nf;
    out[15] = 0;
    return out;
};

/**
 * Generates a orthogonal projection matrix with the given bounds
 *
 * @param {mat4} out mat4 frustum matrix will be written into
 * @param {number} left Left bound of the frustum
 * @param {number} right Right bound of the frustum
 * @param {number} bottom Bottom bound of the frustum
 * @param {number} top Top bound of the frustum
 * @param {number} near Near bound of the frustum
 * @param {number} far Far bound of the frustum
 * @returns {mat4} out
 */
mat4.ortho = function (out, left, right, bottom, top, near, far) {
    var lr = 1 / (left - right),
        bt = 1 / (bottom - top),
        nf = 1 / (near - far);
    out[0] = -2 * lr;
    out[1] = 0;
    out[2] = 0;
    out[3] = 0;
    out[4] = 0;
    out[5] = -2 * bt;
    out[6] = 0;
    out[7] = 0;
    out[8] = 0;
    out[9] = 0;
    out[10] = 2 * nf;
    out[11] = 0;
    out[12] = (left + right) * lr;
    out[13] = (top + bottom) * bt;
    out[14] = (far + near) * nf;
    out[15] = 1;
    return out;
};

/**
 * Generates a look-at matrix with the given eye position, focal point, and up axis
 *
 * @param {mat4} out mat4 frustum matrix will be written into
 * @param {vec3} eye Position of the viewer
 * @param {vec3} center Point the viewer is looking at
 * @param {vec3} up vec3 pointing up
 * @returns {mat4} out
 */
mat4.lookAt = function (out, eye, center, up) {
    var x0, x1, x2, y0, y1, y2, z0, z1, z2, len,
        eyex = eye[0],
        eyey = eye[1],
        eyez = eye[2],
        upx = up[0],
        upy = up[1],
        upz = up[2],
        centerx = center[0],
        centery = center[1],
        centerz = center[2];

    if (Math.abs(eyex - centerx) < GLMAT_EPSILON &&
        Math.abs(eyey - centery) < GLMAT_EPSILON &&
        Math.abs(eyez - centerz) < GLMAT_EPSILON) {
        return mat4.identity(out);
    }

    z0 = eyex - centerx;
    z1 = eyey - centery;
    z2 = eyez - centerz;

    len = 1 / Math.sqrt(z0 * z0 + z1 * z1 + z2 * z2);
    z0 *= len;
    z1 *= len;
    z2 *= len;

    x0 = upy * z2 - upz * z1;
    x1 = upz * z0 - upx * z2;
    x2 = upx * z1 - upy * z0;
    len = Math.sqrt(x0 * x0 + x1 * x1 + x2 * x2);
    if (!len) {
        x0 = 0;
        x1 = 0;
        x2 = 0;
    } else {
        len = 1 / len;
        x0 *= len;
        x1 *= len;
        x2 *= len;
    }

    y0 = z1 * x2 - z2 * x1;
    y1 = z2 * x0 - z0 * x2;
    y2 = z0 * x1 - z1 * x0;

    len = Math.sqrt(y0 * y0 + y1 * y1 + y2 * y2);
    if (!len) {
        y0 = 0;
        y1 = 0;
        y2 = 0;
    } else {
        len = 1 / len;
        y0 *= len;
        y1 *= len;
        y2 *= len;
    }

    out[0] = x0;
    out[1] = y0;
    out[2] = z0;
    out[3] = 0;
    out[4] = x1;
    out[5] = y1;
    out[6] = z1;
    out[7] = 0;
    out[8] = x2;
    out[9] = y2;
    out[10] = z2;
    out[11] = 0;
    out[12] = -(x0 * eyex + x1 * eyey + x2 * eyez);
    out[13] = -(y0 * eyex + y1 * eyey + y2 * eyez);
    out[14] = -(z0 * eyex + z1 * eyey + z2 * eyez);
    out[15] = 1;

    return out;
};

/**
 * Returns a string representation of a mat4
 *
 * @param {mat4} mat matrix to represent as a string
 * @returns {String} string representation of the matrix
 */
mat4.str = function (a) {
    return 'mat4(' + a[0] + ', ' + a[1] + ', ' + a[2] + ', ' + a[3] + ', ' +
                    a[4] + ', ' + a[5] + ', ' + a[6] + ', ' + a[7] + ', ' +
                    a[8] + ', ' + a[9] + ', ' + a[10] + ', ' + a[11] + ', ' + 
                    a[12] + ', ' + a[13] + ', ' + a[14] + ', ' + a[15] + ')';
};

if(typeof(exports) !== 'undefined') {
    exports.mat4 = mat4;
}