When a model is opened, the display window is created (see Fig.
When the mouse moves over the display, a red label appears and shows the position of the reference frame. The position of the reference frame can be changed by selecting either translation or rotation above the display. Now, when clicking the left of middle button and moving on the display changes the position of the reference frame. Click the right button to update the changes (the mouse must still be on the display).
The two first buttons under the display controls the zoom. They simply change the physical width and height of the window (parameter size). The zoom factor can be modified through the parameter menu. The last buttons rotate the model. The rotation angle is written at the lower right and can be modified.