In the open source world there are 2 (maybe 3) geometry kernels that handle NURBS and can produce STEP files. Open Cascade, which is GPL now but had a commercial origin. It's quite good and is used in FreeCAD, Salome, KiCAD (EDA), Horizon EDA, Dune 3d, and probably several more. And then Solvespace which is the only user of it's own bespoke kernel which we are still trying to make more robust. This one is also limited to a certain subset of NURBS constructs but is still quite useful.
Open Cascade may be the most difficult piece of FLOSS IP to recreate outside the Linux Kernel. In fact I'd say it'd be harder to replace given the number of people with interest and the background to work on these two different type of software.
Thank you so much for all the work you and your colleagues do to bring solvespace to the world.
I believe it has the potential to be one of — and probably already is in — a class of super impactful, all time classic pieces of software alongside the likes of Firefox, Gimp, Inkscape, et al.
Thank you so much for that comment. How you see solvespace is why I started contributing to it. I saw it as fundamentally different and very cool, but it had a lot of shortcomings that I felt capable of addressing. Unfortunately I haven't given it much time lately (personal happenings). I wanted to put out version 3.2 about 2 years ago, and it's been "almost there" ever since. We will get there though. Comments like yours really help when its volunteer work! Thanks agian.
Agreed, though I would put it in a more rarified category of "Opensource software which has innovated in terms of interface in a unique and meaningful fashion." --- other tools I put in this space are:
>> Will geometry kernels ever be fully robust, or is there still a holy grail to be discovered here?
WRT robustness maybe not. Even the commercial ones tend to fail in certain situations. I'm not sure if there's a widely desired holy grail people are looking for and I don't even know what that would look like. I might recognize it if it appeared, but maybe not.
BTW for FEA I think a major new thing is available in Altair products the last couple years.
What about one of those SDF code CADs but with FreeCAD's sketcher as the UI?
I'd imagine extruding a sketch into an SDF object is possible, and you could just only allow sketches to reference stuff in other sketches, or the bounding box cube of a sketch extrusion.
They'd need some better tools for referencing stuff between sketches but other than that, it seems like it's mostly all there.
And then at the end if you wanted a STEP I'm sure someone out there has got to be working on some kind of mesh to STEP thing that properly preserves design intent.
I am pretty sure that this is a consequence of the mathematics for modeling this being _very_ hard, and a robust (and performant) solution requiring as-yet undiscovered/unpublished mathematics.
>> Solvespace only seems to have simple STEP export...
And it will probably stay that way. STEP is a huge specification and solvespace only supports a small subset of the features of it. In particular it doesn't do complex NURBS curves or surfaces, it only supports rational Bezier curves and surfaces up to degree 3. It does support trimmed surfaces which result from boolean operations and which most other OSS NURBS libraries do not handle.
Some day I'd like to get it to import what it can - particularly its own output - but that's a very low priority since it would be quite limited.
BTW gcad3d has fairly extensive STEP I/O with its own GPL3 C code (so we could start with that). I'm still not sure what that tool is mostly for - it seems to be more for CAM simulation? but I'm not sure.
I would use the STEP I/O library from Open Cascade (or BRL-CAD), they are closer to how we expect someone to read and write STEP models, neither are really tied to the parent CAD system. The one in BRL-CAD does have problems compiling a feature of the latest STEP standards.
One thing missing from the subject of the thread was any history of the exchange formats.
