1. A method comprising: locating an initial position of a face based on visual detection, by a mobile device, of a user's pair of eyes; determining, based on the initial position, a first viewpoint relative to a screen of the mobile device; rendering a first image of a constructed scene on the screen based on the first viewpoint; after determining the initial position based on the visual detection, monitoring subsequent movement through input received from an accelerometer of the mobile device, to determine a distance of the face from the initial position; determining, based on the distance of the face from the initial position and without further visual detection, a subsequent position of the face; determining, based on the subsequent position, a second viewpoint relative to the screen; and rendering a different image of the constructed scene on the screen based on the second viewpoint.