Full Version: Step conversion errors.

Hiya.
Been using MOI for years, and love so many aspects. Becoming concerned recently though; STEP files we're recieving aren't being read correctly.

It's becoming more common, and we assumed it was due to the CAD engineers of our client. Possibly lazy modelling, etc.
Now we're seeing errors from two other clients, and it's got to the point we can't trust MOI any more. Has there been a change in the STEP format recently ? ( in the last year or so)

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Hi Rico, it's hard to tell what could be going on just from a description like that. I need to see actual files that are having problems to be able to give any good information on what's happening. If you need to keep them private you can e-mail them to me at moi@moi3d.com .


> Has there been a change in the STEP format recently ? ( in the last year or so)

Well, MoI version 4 has come out within the last year and it does have an upgrade to the STEP library that it uses. But it is a new version of the same library that it has been using for a long time.

Do you mean that the same STEP files are coming in differently into MoI version 3?


One thing you can try for problematic STEP files is to use CAD Exchanger to convert the STEP file into a version 5 .3DM file and then read the .3dm file into MoI.

- Michael

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Hi Micheal,
I do appreciate that it's hard to toubleshoot without having your hands on the offending data - I'm just awaiting permission now to send a sample STEP to you. NDA's etc.

And thank you for the advice. :)

I'd not heard of CAD exchanger - that was helpful, thank you! Interestingly, it looked as it should in CAD Exchanger, though no matter what STEP version I put out from it, the same errant meshes happened in MOI.
Also: MOI simply hung when trying to load a version that was output as .3DM (regardless of what version I set it to).

Again, I know this is of little use to you until you recieve a file - will get one to you asap (monday at earliest, by the looks of it) so no rush.
/RH

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Hi,

Here are a couple of STEP files that I recently downloaded from one of my vendors.

With the most recent version of MOI one of them imports fine, the other not so good.

Frederick

Attachments:
Two_Step_Files_One_Good_One_Bad.zip

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Hi Frederick, thanks for posting these. The bad one is a bug in processing a particular kind of "degenerate toroidal" surface (relatively rarely seen). I've got a fix prepared for that for v5.

I've attached the result that v5 will have for this file.

- Michael

Attachments:
3786N12_Linear Sleeve Bearing.3dm

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Hi,

Thanks for providing a useable version of the STEP file that did not process correctly.

Frederick

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Hello Michael,

I can confirm RHolmes' issue with STEP file import in V4, while V3 shows no problem during import of the same file.
Here is the file example. Maybe it helps in regard to bug fixing. I did the export in SolidEdge 2019, based on prior obj import.

Regards,
Martin

Attachments:
tex.stp

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Hi Martin, that STEP file contains triangle mesh data, not CAD surfaces and solids which is what MoI is generally expecting to be in a STEP file.

I'll take a look at why it would load in MoI v3 and not in v4 but I do not generally expect for this type of faceted triangle mesh data to load well into MoI in the first place. I don't recommend trying to work with polygon data in MoI, it's not designed for that.

- Michael

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Hi Michael,

Thanks for the advice. I use this workaround in Moi based on such STEP files to transfer polygon/stl mesh to cleaned up solid models for hard surface modeling.
As mentioned, in V3 there are no issues with that.

Good luck with the analysis.
Regards,
Martin

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Hi Martin, so yes this has to do with the particular kind of mesh entity in your STEP file, the STEP "FACETED_BREP" entity type. This is a separate issue from what Rico wrote about above.

Moi v3 did load the "FACETED_BREP" entities but that got broken in v4 since the Jun-6-2018 v4 beta release which reworked the STEP importer to use multiple CPU threads.

This is the first time it's been reported in the last 3 years because it's kind of an obscure and rarely used area. I'll see about restoring the v3 behavior for the first v5 beta release.

Thanks for reporting it and sending the file!

- Michael

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