It is proposed that the 3-D representation of an object is based primarily on a stick-figure configuration, where each stick represents one or more axes in the object's generalized cylinder representation. The loosely hierarchical description of a stick figure is interpreted by a special-purpose processor, able to maintain two vectors and the gravitational vertical relative to a Cartesian space-frame. It delivers information about the appearance of these vectors, which helps the system to rotate its model into the correct 3-D orientation relative to the viewer during recognition.
