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

    QVector3D nearPlane(conv_x, conv_y, -1);
    QVector3D farPlane(conv_x, conv_y, +1);

    //Multiply per the inverted ModelView matrix, to get world space coordinates
    nearPlane = nearPlane * cam_m.inverted(); // 3d vector * 4x4matrix...
    farPlane = farPlane * cam_m.inverted();

    QVector3D direction = nearPlane - farPlane;