3D Interoperability

[rln]

Hello folks,

Does the SAT format support storing a face which is shared by two (or more) shells, i.e. non-manifold case ?

SAT documentation says that the face entity has a 'next' field which refers to the face in the same shell (i.e. linked list pattern). When a face belongs to two shells obviously next may only refer to the next face in one of the shells.

I encountered this issue when working on CAD Exchanger (http://www.cadexchanger.com) when one of the users complained that he could not convert a model from BRep to ACIS with such non-manifold topology.

Thank you in advance for your help.

Roman

[Vivekan]

Hi Roman,

Are you using ACIS to construct geometry from the translated model? If yes, it would be helpful if you can submit the ACIS APIs you are using for construction to Spatial Support.

Thanks,

Vivekan

[rln]

Hi Vivekan,

No. The original model is not in ACIS but in another format (original model from the user was in Open CASCADE BRep, but presumably it can be some other format, e.g. IGES Group entity type 402 or STEP shell, etc). Unlike ACIS-SAT format which encodes child faces as a linked list (i.e. each face has a reference to a next one), in these formats a parent directly refers to its children (i.e. contains a list of references).

During translation each entity is stored in the map and if the same object is referred twice, it is retrieved from the map and inserted into a new instance. This way ensures sharing of edges or vertices for instance. Now the question comes about faces which seem to not suppose such multiple sharing by parents.

Hope this helps.

Roman

P.S. I'm currently not a Spatial customer yet though still consider this option. My users need to export data from their OpenCASCADE-based applications into downstream applications which seem to be ACIS-based therefore they come to use CAD Exchanger in order to export into ACIS-SAT.