| Lens: To place the lens, click at the point above the central axis where you want the top of the object to appear. The new lens is centered on the central axis. The lens refracts all incident light. When the Select button is pressed, you can move and resize the lens. You can also change the focal length of the lens by click-and-dragging on the hotspots indicated below.
| Another way to set the focal length is to choose a value in the lens's Properties Box. The Properties Box also lets you select the curvature of the lens. You can make it convex (default) or concave. You can also choose to display the lens's two foci (they appear as Xs on the central axis).
An alternative view of this object is available.