public Quaterniond add(Quaterniond q) {
        return add(q.x, q.y, q.z, q.w);
    }
public Quaterniond add(Quaterniond q) {
        return add(q.x, q.y, q.z, q.w);
    }
public Quaterniond add ( Quaterniond q ) { return add ( q . x , q . y , q . z , q . w ) ; }
Adds another quaternion to this one.

@param q The quaternion to add
@return A new quaternion, which is the sum of both
Adds another quaternion to this one .