When you design 3D shapes in the context of a background picture, you can easily switch
from 2D to 3D. This improves the manipulation and the design of your geometrical
elements.
In the background of your picture, click and drag.
The appearance of the pointer is modified and the view switches to 3D.
To switch back to 2D, click Switch 2D/3D View from the
Photo section of the action bar.