Build123d: A Python CAD programming library
by Ivoah on 3/29/2026, 8:58:22 PM
https://github.com/gumyr/build123d
Comments
by: injidup
These types of CAD scripting tools are great but always try to position themselves as an “alternative” to GUI-driven CAD, whereas in reality they are complementary. OnShape got it right with FeatureScript (<a href="https://cad.onshape.com/FsDoc/" rel="nofollow">https://cad.onshape.com/FsDoc/</a> ), which provides a very similar experience to Build123d at the scripting level. However, the insight that OnShape got right is that these scripts automatically become available as possible nodes within the history-based modeller. The OnShape UI is infinitely extendable beyond the fixed set of tools that comes with the base modeller.<p>Build an FOSS CAD front end using something like Build123d as the extension engine, and then add hooks so the user can select edges, surfaces, objects, etc., and feed them to inputs on the scripts. The output of the script is then the new state of the history-based modeller. That would be killer
3/30/2026, 3:38:21 PM
by: nakedneuron
as someone mentioned recently somebody made this build123d-playground on the web:<p><a href="https://jojain.github.io/build123d-sandbox/" rel="nofollow">https://jojain.github.io/build123d-sandbox/</a><p>learning curve is steep, but the examples get you going in no time..<p>though not really CAD, favorite example: <a href="https://build123d.readthedocs.io/en/latest/examples_1.html#canadian-flag-blowing-in-the-wind" rel="nofollow">https://build123d.readthedocs.io/en/latest/examples_1.html#c...</a><p>shows the ability of this implementation of the open cascade kernel.. i havent found this kind of projection function too often in other cad programs, so this is really cool.. i remember trying to do similar with ptc creo and it was a pain..
3/30/2026, 4:08:12 PM
by: latenode
CAD has needed a proper code-first workflow for years. The existing options always felt like they were built for the GUI first and scripting was bolted on after.
3/30/2026, 4:03:46 PM
by: wisemanwillhear
In many ways this looks fun. I love the precise control and programming power of tools like this, but when I need something in real life, I never use them any more. The productivity of graphical tools is so much greater (as far as my brain works).<p>When I was younger I used POVray for a few small projects, but once I had access to graphical interfaces the difference in output quantity and quality was huge. I still keep tools like POVray installed, but all I ever do with them is tinker once in a while.
3/30/2026, 4:19:16 PM
by: htgb
Despite being aware of its existence, I stuck with OpenSCAD out of habit. Only last week did I read through the documentation, and feel strongly that I've been missing out… it seems to solve all of my gripes with OpenSCAD. I'm excited to try it out!
3/30/2026, 3:40:51 PM
by: z3ugma
I have been using this library for a few months alongside Gemini 3.1 Fast<p>It's really useful to get an iteration loop going with an LLM.<p>The OCCP viewer extension for VS Code helps make sure you can see and manipulate the resulting model
3/30/2026, 3:47:06 PM
by: jpleger
This is cool, seems like a next gen cadquery, which was really cool to see.
3/30/2026, 4:47:11 PM
by: CarVac
I like Build123d but I really want a hybrid mouse/code CAD built around it. I want to be able to click on entities and have them show up in the code editor instead of blindly trying to select edges.
3/30/2026, 3:46:29 PM