Geomview look commands

[fowler]

I just checked a version of transform.c back in which includes the
following new commands:

(look-toward [objectID] [cameraID] [origin | bbox]
        Rotates the named camera to point toward the origin of the
        object's coordinate system, or the center of the object's
        bounding box.  Default objectID is the world, default camera
        is targetcam, default location to point towards is the center
        of the bounding box.

(look-encompass [objectID] [cameraID])
        Moves cameraID backwards or forwards until its field of view
        surrounds objectID. It will be impossible if the camera is in
        hyperbolic or spherical space.  If objectID is not specified, it
        is assumed to be the world.  If cameraID is not specified, it is
        assumed to be the targetcam.

(look [objectID] [cameraID]
        Rotates the named camera to point toward the center of the
        bounding box of the named object, then moves the camera
        forward or backward until the object appears as large as possible
        while still being entirely visible.  Equivalent to
        progn (
                (look-toward [objectID] [cameraID])
                (look-encompass [objectID] [cameraID])
        )
        If objectID is not specified, it is assumed to be World.  If
        cameraID is not specified, it is assumed to be targetcam.

(look-recenter [objectID] [cameraID]
        Translates and rotates the camera so that it is looking in the
        -z direction (in objectID's coordinate system) at the center of
        objectID's bounding box with the camera as close as possible
        to the object for the entire object to be visible.  Also makes
        sure that the y-axes of objectID and cameraID are parallel.