STEP import - missing lines

Hey there!

I have an issue where importing STEP files into Rhino always skips all curves/lines, although other geometry imports just fine. When importing the files into other CAD software the curves are present.

The STEP files are always exported by the same software. Could also be that it’s export is a little wonky…

Tested with:
Rhino 6 SR28 (6.28.20199.17141, 17.07.2020) - lines missing
Rhino 7 WIP (7.0.20238.17095, 25.08.2020) - lines missing
AutoCAD - lines present
Creo Parametric - lines present

I’ve exported and attached a simple example STEP. It should look like this (two yellow lines on top side of cube)

Rhino import:

Example STEP file:

I’m terribly sorry for double posting and topic bumping, but it’s been a while and still no replies. I can provide more examples if necessary.

Sorry again!

No curve visible with the app above.

However, Autodesk viewer shows your line.

Hello - I see… the object is imported as a block - that it it was an assembly, I do not know if that comes into play in how the curves are presented. I’ll put this on the pile for the developer to look at.
Thanks for the example.

RH-60481 Open:Step - no curves


There are some entities I haven’t seen before associated with the curves. It should not be very difficult to process them. Thanks for the report. [Edit] See my recent comment about an error in the STEP file. That’s the real problem, and I’ve just submitted the code to fix it for V7.

Thanks for the replies. Much appreciated!

Here’s Youtrack bug report.
RH-60546 STEP import misses curves

There is a repeated error in the STEP file. The missing curves are TRIMMED_CURVE entities. Such entities have a field to say whether the curve should be trimmed by a parameter or by 3D point. Both of the curves say they are trimmed by parameter values, but the trimming entity is not a parameter, it is a 3D point. When I search for the trimming parameter, none is found. I should be able to fix this easily enough by looking for a 3D point when no parameter is found.

RH-60546 is fixed in the latest BETA

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I’ve successfully imported a few other problematic STEP files into the latest Rhino 7 Beta. All curves are there now. Thanks again!

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