In the above work, the authors did

In the above work, the authors did not consider undercut features. For some undercut features such as through-holes, they should be ‘patched’ up before the BRDO can be performed in BBA and the surfaces classified in EBA. For the generation of local tools such as side-cores, side-cavities, form pins, etc. the geometry of the undercut features should be extracted for the creation of the ‘heads’ of the local tools. Therefore, all the undercut features should be identified before the core/ cavity blocks can be generated.