Mat33.js

/*
 *  Row major memory layout
 *
 *   0   1   2
 *   3   4   5
 *   6   7   8
 *
 *  equivalent to the column major OpenGL spec
 *
 *   0   3   6
 *   1   4   7
 *   2   5   8
 *
 *  m00 m10 m20
 *  m01 m11 m21
 *  m02 m12 m22
 */

export function create() {
    return [
        1,0,0,
        0,1,0,
        0,0,1
    ];
}

export function equals(a,b) {
    return a[ 0] == b[ 0] &&
        a[ 1] == b[ 1] &&
        a[ 2] == b[ 2] &&
        a[ 3] == b[ 3] &&
        a[ 4] == b[ 4] &&
        a[ 5] == b[ 5] &&
        a[ 6] == b[ 6] &&
        a[ 7] == b[ 7] &&
        a[ 8] == b[ 8] &&
        a[ 9] == b[ 9];
}

export function set9(a,b00,b01,b02,
              b10,b11,b12,
              b20,b21,b22){
    a[0] = b00; a[1] = b01; a[2] = b02;
    a[3] = b10; a[4] = b11; a[5] = b12;
    a[6] = b20; a[7] = b21; a[8] = b22;
    return a;
}

export function set(a,b){
    a[0] = b[0]; a[1] = b[1]; a[2] = b[2];
    a[3] = b[3]; a[4] = b[4]; a[5] = b[5];
    a[6] = b[6]; a[7] = b[7]; a[8] = b[8];
    return a;
}

export function identity(a){
    a[0] = a[4] = a[8] = 1;
    a[1] = a[2] = a[3] = a[5] = a[6] = a[7] = 0;
    return a;
}

export function fromMat4(a,b){
    a[ 0] = b[ 0]; a[ 1] = b[ 1]; a[ 2] = b[ 2];
    a[ 3] = b[ 4]; a[ 4] = b[ 5]; a[ 5] = b[ 6];
    a[ 6] = b[ 8]; a[ 7] = b[ 9]; a[ 8] = b[10];
    return a;
}

export function fromQuat(a,b){
    var x = b[0];
    var y = b[1];
    var z = b[2];
    var w = b[3];

    var x2 = x + x;
    var y2 = y + y;
    var z2 = z + z;

    var xx = x * x2;
    var xy = x * y2;
    var xz = x * z2;

    var yy = y * y2;
    var yz = y * z2;
    var zz = z * z2;

    var wx = w * x2;
    var wy = w * y2;
    var wz = w * z2;

    a[0] = 1 - ( yy + zz );
    a[3] = xy - wz;
    a[6] = xz + wy;

    a[1] = xy + wz;
    a[4] = 1 - ( xx + zz );
    a[7] = yz - wx;

    a[2] = xz - wy;
    a[5] = yz + wx;
    a[8] = 1 - ( xx + yy );

    return a;
}