Transfer of Curved Members

Exporting a GENSEC with only a straight segment goes out as a Packet 10 element: with just a curve segment it goes out as a Packet 60 element. Compound GENSECs are split on export. Imported curved segments will be GENSECs and new straight segments will also be GENSECs. However, if you are merging with an existing model and the interface can identify the source member that was originally a SCTN, it will remain a SCTN. If the application attributes are set, you can rebuild the GENSEC.

SDNF does not have the same concept of complex curved beams as there is in the application. Packet 60 arc members are just circular arcs. Therefore for export a complex curved beam in the application must be split into its straight and arc segments. These are passed through to SDNF with an annotated :SDNFMARK attribute. If the member is part of a GENSEC the :SDNFMARK value has a suffix of ".S<n>" or ".C<n>" indicating a straight or curved segment. The <n> indicates the segment's sequence position. These suffices allow us to rebuild the complex GENSEC if these values are returned to the application from the other system.

If the distance between neighbouring segment end points is outside the tolerance limits, SDNF attempts to build a new GENSEC starting from the next unused segment. The new GENSEC's :SDNFEMARK or :SDNFMARK attributes have a suffix .PART<int>, from 2 upwards. No imported members are lost. In the Compare and Merge process, this new part appears as an ADDED member while the original part indicates as having changed, as it has a reduced number of points.

However, if you can restore a GENSEC in the application it may well be different from its original as the types of CURVE element are normalised to be THRU based curves.

New straight linear members may be replaced by GENSECs according to the !!sdnfSCTNtoGENSEC flag. Members that are already SCTN elements in the model are not changed.

Comparing GENSECs is only down to the point count level on the spine. The actual point attributes are not investigated, except for the start and end points. If there are the same numbers of POINSP and CURVE members respectively these are checked. Any alteration to these numbers indicates changes. They must be inspected visually for comparisons. The re-imported CURVE element are likely to have changed because we only import 1 type - a THRU point, although there are 6 or 7 different types of CURVE points in the application, each with different attribute combinations.