It is a little incorrect to imply that 3D forces the viewer to "look" at parts of an image differently than 2D. That is really a function of Depth of Field (DOF) and is just as evident in 2D photography/cinematography as it is in 3D. Most directors and cinematographers are fairly traditional in their selection of aperture/lens, whether there is one lens or two lense (both options exist for 3D while of course only one lens is used for 2D). And the technique to have a very deep DOF is available to both formats too, allowing the viewer to "look about" in the frame more freely. James Cameron ironically even talked about the technique recently, and used both in Avatar, depending if he wanted the viewer to "explore". But usually, most directoras have wanted the audience drawn onto the subject, particularly during dialogue delivery with shallower depth of field. That is an effective way to "direct" the audience and how they see the film. But to imply 3D forces the audience to see one thing or depth more than 2D is incorrect. Additionally some 3D films, including the new "Alice in Wonderland" are actually filmed single camera in 2D and then "dimensionalized" to 3D in post-production.