Print at Jun 6, 2020, 1:30:41 AM

Posted by Jonnie63 at Aug 11, 2019, 12:29:39 PM
Re: Import and export to autocad
Hi Hmerchen,

I used to work on the code used under Solidworks and other solid modelling platforms - I have worked on translation code professionally.

If you simply mean import and export of 2D plans it might not be so difficult especially if you can stick to lines, circles and ellipses but you mention obj which implies you are thinking of 3space?

Importing successfully to a solid modeller or 3D CAD system is not a simple translation exercise if you want to deal with anything other than the OBJ format which reduces everything to facets ( triangles ).

It is not the experts playing "dumb" - people take various 3D reps for granted these days - dinosaurs in hollywood CGI but most of those models would never import successfully into CADCAM systems because they have very little precision or meaning built into the model.

Most CADCAM systems could only import those models as hundreds of sheets of surface shape but with no understanding of connectivity.

By means of an analogy.

Compare a car where no part is joined to any other but the parts are held in space at approximately the right positions and very nearly the right geometries with odd gaps and places where items that are intended to butt together neatly but due to imprecision actually overlap (matter within matter) with a car where all parts are correctly joined together including precision engineered parts.

Its not the software people playing dumb - its more that CADCAM software does an incredibly complicated job that most users never appreciate, incredibly complex.

In general if you want to share geometry and topology between modelling systems you need to either spend huge amounts of time hiring expert developers or you need to simplify the language you use to communicate between one system and another which brings us to planes and lines - ie triangles and the OBJ format. As soon as you go beyond linear and planar geometry it gets complex very quickly indeed.

The people who write translation software usually have access to the code of the target system, the one you wish to import to - its not a matter of just understanding geometry and connectivity.

Trivially one system working to a resolution of 1.0e-8 in a 1000 x 1000 x 1000 workspace will perceive and get upset by gaps between faces in a model produced by a different system working to a lower precision - things will no longer join up correctly when examined by code working to a higher resolution and the model will fail to work correctly and there starts a huge process of writing complex healing code.

I know the above sounds like I am taking it to extremes but believe me I am not - the user is shielded from so much complexity in modern CADCAM systems but it is there.