Hi,

Lately I've been trying out beegraphy which is an online parametric NURBS-modeller.
It's a beta release and one thing thats clearly a bit strange is the STEP-export.
What got me confound is that Moi3d, Rhino and Fusion 360 will interpret the step-file different.
Here's what it looks like in beegraphy, Moi, Rhino and Fusion.
Any ideas how different software can interpret it differently, clearly the export from beegraphy is messed up, but still!?

Hi renklint, the difficult thing with CAD data transfer is that different CAD programs can represent trimming boundaries in different ways and one of the biggest things is that some allow a trimming edge to cross over the "seam" of a closed surface while others (including MoI and Rhino) don't allow a 3D edge curve to cross over the UV seam.

So there is some conversion processing that happens particularly with trim boundary edges on closed surfaces. The conversion involves some fairly tricky operations to cut edges at the seam crossing. There are various situations that can make that cutting difficult like if an edge runs nearly coincident to the seam edge but meanders back and forth slightly, things like that.

- Michael

Hi Michael,

Is this torus suffers from this same "limitation" ? (I don't care that much tho, unlikely I will use that product)

Hi PaQ,

re:
> Is this torus suffers from this same "limitation" ? (I don't care that much tho, unlikely I will use that product)

No this seems to be a different problem.

If you edit the line in the file that has this:

#21 = EDGE_CURVE('',#22,#22,#24,.T.);

to this:

#21 = EDGE_CURVE('',#22,#22,#24,.F.);

then it appears to come in ok. It will take me a bit to figure out if it's something that is being interpreted wrong by MoI or whether it's an error in the file structure.

- Michael

Oki ! Nothing really important really ... all I can say is that it opens 'fine' in CAD Assisant (don't even remember why I have that thing installed).

Also it was supposed to be a boolean between a torus and a sphere, only get the donut exported obviously ... might as well be something wrong with that Beegraphy stuff.

Maybe take a look at this free one online (Beegraphy on steroids! ;)

https://cables.gl/

Interesting.
I made the same geometry from scratch in Moi and when I export that as STEP it opens correctly in Rhino and Fusion.
But obviously it's not constructed exactly the same as the model in beegraphy, so maybe I can't compare the result.

I found a workaround and have notified the beegraphy-team.
By extruding a surface instead of a curve the export works great and can be imported in Moi, Rhino and Fusion.
Thanks for the explanation why imported CAD-data might differ in different software.