Proper use of the AcBr library involves interactions between several internal and external objects: AcBrEntity, AcBrTraverser, and their derived classes; AcDbFullSubentityPath and its components from the AcDb library (AcDbObjectId, AcDbSubentId, and so on); and geometry objects from the AcGe library (AcGeSurface, AcGeCurve3d, AcGePoint3d, and so on).
In a boundary representation model, topological objects are used as the “glue” that holds the model together, and geometric data is referenced by the topological objects. To access the details of a boundary representation model's shape, you may either traverse the topological objects (using a traverser) or proceed directly to a topological object of interest (using the AcDbFullSubentPath corresponding to a screen pick).