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

    //Get viewport points as begin and end of the ray
    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 of those points
    QVector4D nearPlane2 = cam_m.inverted() * nearPlane;
    QVector4D farPlane2 =   cam_m.inverted() * farPlane;


    //direction, farPlane - nearPlane
    QVector4D direction = farPlane2 - nearPlane2;