Load IGES 106 entity and try to save it back to IGES 106 entity

Hi Guys,

I have a problem of saving IGES. I have an IGES file which contains entity 106 curves which are non-rational b-spline. When I open it using OCC and save it back to IGES file, it becomes IGES 126 entity. It exports all weights of control points to the new IGES file. My question is it possible to save non-rational curves to IGES 106? I can't find those configuration options.
Thanks in advance.


Cauchy Ding's picture

Just fixed it by using Handle_IGESGeom_CopiousData and using AddEntity of IGESControl_Writer.

Forum supervisor's picture

Dear Cauchy,
Note that IGES enity 106 (Copyous Data) does not represent arbitrary non-rational B-Spline, but (in forms 11, 12, 63) just a polyline with specific parameterization (by curve length).
Though OCCT converts such entities to B-Spline curves on import, reverse conversion would be applicable only for B-Splines of degree 1 and with that parameterization.
This is not typical for CAD models, and we deem that writing B-Splines of degree 1 as entities 106 may cause problems in some target systems.

Nevertheless you are welcome to contribute your improvement: this feature it can be disabled by default and enabled if needed by dedicated option.
See OCCT developer portal on how to contribute: http://dev.opencascade.org/index.php?q=home/get_involved

Best regards

Cauchy Ding's picture


Thank you for your reply. This exporting feature is only for a CAE function.