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From the 13th version of GiD, a new system of problemtye has been implemented (based in the CustomLIB library). Although the 'classic' problem type system is still supported by GiD, it is considered deprecated, as the new one offers clear advanteges in terms of usability, performance and integration cappabilities. Documentation about the deprecated classic problem type system can be found in the annex of this manual APPENDIX B (classic problemtype system).
This new problem type definition uses a single .spd file to describe general properties, materials, conditions and units (as a tree with xml syntax). All this data is showed in a 'tree view', and materials and conditions are associated to groups of enties.
About writting the input file, Tcl commands are used to write the data in files (optionally aided with the special funcion GiD_WriteCalculationFile for efficiency).
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