qreal conv_x = ( (mousex / (854.0/2.0)) -1);
    qreal conv_y = ( (mousey / (480.0/2.0)) -1);

    QVector4D nearPlane(conv_x, conv_y, -1, 0.0);
    QVector4D farPlane(conv_x, conv_y, +1, 0.0);

    //Multiply per the inverted ModelView matrix, to get world space coordinates
    QVector4D nearPlane2 = nearPlane * cam_m.inverted();
    QVector4D farPlane2 = farPlane * cam_m.inverted();

    QVector4D direction = farPlane2 - nearPlane2;