[ІГРОГРАЙКО]

Есть! нашел в том же файле (glMatrix.js)...

/**
* Stores the angle and axis in a vec4, where the XYZ components represent
* the axis and the W (4th) component is the angle in radians.
*
* If dest is not given, src will be modified in place and returned, after
* which it should not be considered not a quaternion (just an axis and angle).
*
* @param {quat4} quat the quaternion whose angle and axis to store
* @param {vec4} [dest] the optional vec4 to receive the data
*
* @returns {vec4} dest
*/
    quat4.toAngleAxis = function(src, dest) {
        if (!dest) dest = src;
        // The quaternion representing the rotation is
        // q = cos(A/2)+sin(A/2)*(x*i+y*j+z*k)

        var sqrlen = src[0]*src[0]+src[1]*src[1]+src[2]*src[2];
        if (sqrlen > 0)
        {
            dest[3] = 2 * Math.acos(src[3]);
            var invlen = glMath.invsqrt(sqrlen);
            dest[0] = src[0]*invlen;
            dest[1] = src[1]*invlen;
            dest[2] = src[2]*invlen;
        } else {
            // angle is 0 (mod 2*pi), so any axis will do
            dest[3] = 0;
            dest[0] = 1;
            dest[1] = 0;
            dest[2] = 0;
        }
        
        return dest;
    };

Теперь только матрицу в кватернион конвертнуть...