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Top 23 C++ Cad Projects
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Project mention: Ask HN: What Are You Working On? (February 2025) | news.ycombinator.com | 2025-02-23
I'm a long-time FreeCAD user, and one of my annoyances is that long-running operations lock up the entire UI and can't be aborted.
So for my first contribution to FreeCAD I'm working on fixing this.
The underlying CAD operations are done by "OpenCascade", and at first I thought OpenCascade had no support for aborting operations part of the way through. So my first implementation was to move the operation into a child process and give the user a dialog box that would allow terminating the child process.
But it actually turns out OpenCascade does support aborting the operations! So now I'm working on doing it the OpenCascade way.
My PR is here: https://github.com/FreeCAD/FreeCAD/pull/19796
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Project mention: Simple programming language with offline usable browser IDE | news.ycombinator.com | 2025-05-29
I suppose I should blog about this at: https://designinto3d.com/
but I've written a fair number of posts on it at:
https://forum.makerforums.info/search?q=gcodepreview
and it has come up a few times at:
https://community.carbide3d.com/search?q=gcodepreview
and on the OpenSCAD mailing list --- that latter might need to be extended back in time to encompass: https://github.com/openscad/openscad/issues/2017
Glad to answer any questions you might have!
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LibreCAD
LibreCAD is a cross-platform 2D CAD program written in C++17. It can read DXF/DWG files and can write DXF/PDF/SVG files. It supports point/line/circle/ellipse/parabola/spline primitives. The user interface is highly customizable, and has dozens of translations.
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Project mention: Bezier-rs – algorithms for Bézier segments and shapes | news.ycombinator.com | 2025-08-13
If they could extend it to rational Beziers it might be useful for CAD applications. We have a subset of these in C++ as the core of Solvespace. This is one of my favorite source files:
https://github.com/solvespace/solvespace/blob/master/src/srf...
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kicad-source-mirror
This is an active mirror of the KiCad development branch, which is hosted at GitLab (updated every time something is pushed). Pull requests on GitHub are not accepted or watched.
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InfluxDB
InfluxDB – Built for High-Performance Time Series Workloads. InfluxDB 3 OSS is now GA. Transform, enrich, and act on time series data directly in the database. Automate critical tasks and eliminate the need to move data externally. Download now.
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> Can anyone explain where this blob of "assembly language" comes from?
Assembly language is definitely the right analogy: it's a low-level target generated by higher-level tools. In this case, the expression came from a Python script calling this text(...) function:
https://github.com/mkeeter/antimony/blob/f6a56dd7/py/fab/sha...
The font is hand-built from geometric primitives (rectangles, circles, etc) and CSG operations (union, intersection, difference)
> What is considered an acceptable preprocessing or transformation?
I'm looking for interesting ideas, and to mine the depths of PLs / compiler / interpreter / runtime research. Just returning a fixed image isn't particularly interesting, but (for example) I just updated the site with a compile-to-CUDA example that shows off the brute force power of a modern GPU.
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OCCT
Open CASCADE Technology (OCCT) is an open-source software development platform for 3D CAD, CAM, CAE.
Project mention: OpenSCAD: The Programmer's Solid 3D CAD Modeller | news.ycombinator.com | 2024-09-14OpenSCAD has been great for simple projects. It’s very easy to get productive with if you know basic programming concepts. However, I’ve run into frustrating limitations on more complex projects. The core geometry engine is skittish.
I still use OpenSCAD, but I’m diving into the OCCT ecosystem. It has a steeper learning curve, but seems to be significantly more robust.
https://dev.opencascade.org/
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qcad
QCAD - The Open Source 2D CAD. QCAD is a cross-platform CAD solution for Windows, macOS and Linux. It supports the DXF format and optionally the DWG format (through a proprietary plugin).
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Project mention: Libfive: Solid modeling (CAD) library/tools with Scheme/Python bindings and GUI | news.ycombinator.com | 2025-07-28
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Project mention: The first release candidate of FreeCAD 1.0 is out | news.ycombinator.com | 2024-09-11
I still recommend RealThunder's fork (https://github.com/realthunder/FreeCAD/) at the moment, even though his fork is a bit lagging at the moment.
Most of his contributions to the topology fixes got merged back into freecad now, but his enhancements to UI/behavior aren't (yet), and they make a night and day compared to ondsel too.
I didn't find any significant limitation to RealThunder's assembly3.
In any case, while far from most commercial offerings, FreeCAD is progressing and the future looks bright. I've stopped using f360/onshape in the last years for my hobby designs. Once you know the specific limitations of freecad+occt (something you learn in each cad program) and how to work them around effectively, it's already pretty powerful.
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LibreCAD_3
LibreCAD 3 is a next generation 2D CAD application written to be modular, with a core independent from GUI toolkits. Scripting is possible with Lua.
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Ventilator
Fully-featured ICU ventilator design, optimized for manufacture using commonly available components and free to license. Repository tracks all mechanical, electrical and systems design, software, requirements and regulatory documentation. (by RespiraWorks)
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NOTE:
The open source projects on this list are ordered by number of github stars.
The number of mentions indicates repo mentiontions in the last 12 Months or
since we started tracking (Dec 2020).
C++ Cad discussion
C++ Cad related posts
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Libfive: Solid modeling (CAD) library/tools with Scheme/Python bindings and GUI
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Cppyy: Automatic Python-C++ Bindings
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Proposal: GUI-first, text-based mechanical CAD inspired by software engineering
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Simple programming language with offline usable browser IDE
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Link Time Optimizations: New Way to Do Compiler Optimizations
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The Prospero Challenge
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Add a Workaround to Nahimic Crapware
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A note from our sponsor - Sevalla
sevalla.com | 2 Sep 2025
Index
What are some of the best open-source Cad projects in C++? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | FreeCAD | 25,991 |
| 2 | openscad | 8,161 |
| 3 | LibreCAD | 5,180 |
| 4 | solvespace | 3,535 |
| 5 | LibrePCB | 2,658 |
| 6 | leocad | 2,619 |
| 7 | kicad-source-mirror | 2,322 |
| 8 | antimony | 2,149 |
| 9 | OCCT | 1,750 |
| 10 | mayo | 1,705 |
| 11 | qcad | 1,646 |
| 12 | libfive | 1,533 |
| 13 | FreeCAD | 840 |
| 14 | oce | 840 |
| 15 | CavalierContours | 481 |
| 16 | LibreCAD_3 | 345 |
| 17 | lpub3d | 164 |
| 18 | Ventilator | 147 |
| 19 | OCP | 128 |
| 20 | VisualScriptCAD | 119 |
| 21 | oc | 15 |
| 22 | sse | 15 |
| 23 | ZEDD-VALORANT-SWORD-thingy | 0 |
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