[Bounding Box] command generates bounding box surfaces as the evaluation result of the bounding box of curves or surfaces geometric elements. When the elements are solid ones, it generates 6 faces to constitute a rectagular parallelepiped.
When objects are included on a plane parallel to a coordinate plane ((x,y), (y,z), or (z,x) plane), command generates a rectangle polyline that includes whole objects. The polyline's edges are all parallel to x, y, or z axis.
When objects are a point or a line parallel to an axis, it generates nothing.