Assembly3 preview

[Mark Szlazak]

this generally works only for more simple Assemblies and in this case then the multi-body structure is used (because bodies go in to Parts).

Body are not present at STEP level at all.

It also does not have a specific Assembly or Part container. In general there is only an hierarchical structure, and it is why it is possible to import it in different ways... Anyway, I have already planed to write a few more things in the "Discussion on Parts and Bodies" topic to hopefully represented my views with a bit more details, so I will do that in the next week or two and we will see then if we can come a bit closer with our views.

Yes please write this up as soon as you able. Thank you!

[easyw-fc]

Do you notice the different icons DSM used? It is not that hard to guess which icon is for group, which is for object. I'll say that the green icon has no equivalence in FC.

Here a very simple shape I found in the web:
https://github.com/vancegroup-mirrors/s ... e/cube.stp
This is done in SolidWorks

Code: Select all

FILE_NAME ('Cube2.STEP',
    '2010-05-25T09:32:49',
    ( '' ),
    ( '' ),
    'SwSTEP 2.0',
'SolidWorks 2007',

FYI the green icon has the equivalence in FC as a simple 'Part::Feature' geometry.

simple-cube.gif (353.47 KiB) Viewed 821 times

[realthunder]

FYI the green icon has the equivalence in FC as a simple 'Part::Feature' geometry.

I checked DSM manual. I think the green icon means Solid. And the parent of the green icon, the brownish one is more like FC Part::Compound, or maybe CompSolid, because they have different icon for compound of edges, called Curve. You can try this, import UR10 with upstream, and export it again as STEP. Now open that STEP in DSM, you'll get a different hierarchy. If upstream were to use Part::Compound for those joint, then the round trip will not affect the hierarchy.

[easyw-fc]

I also noticed that on this SolidWorks STEP file
https://github.com/vancegroup-mirrors/s ... roduct.stp

I get a different representation of the loaded file in
1) CAD Assistant of OCC and FC 0.17-0.18

cada-fc.png (122.79 KiB) Viewed 715 times

2) DesignSpark Mechanical

dsm.png (106.05 KiB) Viewed 715 times

3) FC A3 branch

fc-a3.png (88.23 KiB) Viewed 715 times

We definitively need to have someone with access to a commercial CAD like SW, NX, PTC to jump in as tester for STEP In/Out files, otherwise it would be very difficult to tune it without a feedback from what widely used commercial sw do...

[saso]

It is a multi-body part

like this is sort of ok

Untitled.png (13.34 KiB) Viewed 697 times

this would be even better

Untitled1.png (8.78 KiB) Viewed 697 times

but here we can again hit on about our disagreements about bodies...

however, as I said before it is possible to import such step files on different levels, above is the example of importing it on the part level (and is correct for this example since it is a multi-body part), but one could also import it on the assembly level, in this case and IF we would have the proper full implementation of the assembly, parts and bodies, then it should be like this (note the assembly container icon on top and the removed origins from the bodies ). This is also how DSM seems to import it (on the assembly level), does DSM support bodies (multi-body)?

Untitled2.png (21.29 KiB) Viewed 677 times

[easyw-fc]

but here we can again hit on about our disagreements about bodies...

We definitively need to have someone with access to a commercial CAD like SW, NX, PTC to jump in as tester for STEP In/Out files, otherwise it would be very difficult to tune it without a feedback from what widely used commercial sw do...

not only difficult but also useless ...
Moreover we must obtain an exact replica of what is imported, when exported and re-imported.

[nemesis]

We definitively need to have someone with access to a commercial CAD like SW, NX, PTC to jump in as tester for STEP In/Out files, otherwise it would be very difficult to tune it without a feedback from what widely used commercial sw do...

My 2 cts as I don't really understand all the technical stuf here
The file imported with 3DAnalyzer which is only viewer importing a lot of format, and Catia V5R26

CatiaV5R26Import.png (242.09 KiB) Viewed 600 times

Other maybe "dumb" question, shouldn't we use file from here
I tested one just to see the difference.

StepImport.png (485.13 KiB) Viewed 600 times

not only difficult but also useless ...
Moreover we must obtain an exact replica of what is imported, when exported and re-imported.

+1

[easyw-fc]

@nemesis thank you a lot!
I was starting with a comparison of very simple STEP files I found on the web made in SolidWorks

shouldn't we use file from here

yes please
it would be nice to compare the import of these STEP hierarchical files of the same assembly:
https://www.cax-if.org/library/as1-oc-214.zip (this is generated by OCC kernel)
https://www.cax-if.org/library/as1-pe-203.zip (this is generated by PTC kernel)
https://www.cax-if.org/library/as1-tu-203.zip (this is generated by UG NX kernel)

and
https://www.cax-if.org/library/dm1-oc-214.zip (this is generated by OCC kernel)
https://www.cax-if.org/library/dm1-id-214.zip (this is generated by Siemens PLM Software NX kernel)
https://www.cax-if.org/library/dm1-pe-214.zip (this is generated by PTC kernel)

Thx again,
Maurice

[saso]

This is good, but one also has to understand what we are looking at (3DAnalyzer obviously does not support bodies) and understand some of the concepts behind it to understand why both 3DAnalyzer and Catia imported models are actually identical (note that the Geometrical Set.1 in Catia is actually empty, not used). In both cases this are actually just two solids inside a part. And this are also identical to my first and second (part level) imported examples above. And I can tell you that if one knows how to look beyond the differences in the representations of the tree it is all the same in all of the different parametric cad programs.

CatiaV5R26Import.png (229.08 KiB) Viewed 541 times

[easyw-fc]

In both cases this are actually just two solids inside a part.

then the actual importer is doing fine.
And does it sound useful to add a Body container and place a solid inside a Body, considering that FC Body doesn't allow inside a simple Solid?
https://www.freecadweb.org/wiki/PartDesign_Body/en

I think what at the moment is implemented is a good representation of the STEP structure (STEP doesn't have any history of the included shapes).
It can be sure improved, but I think the 'Part' container for the hierarchy is the right one to be used as it is implemented now.