The B U I L D 1 2 3 T H I N G S Library.

This package contains an extension to the brilliant build123d, a Pythonic scripted-CAD system based on Open CASCADE Technology. In build123things, user designs are subclasses of Thing, each such subclass represents a parametric family of objects, i.e., components. With the library, semantically related build123d objects are groupped in Thing instances with following provided functionality and features:

• Reference geometry is managed as attributes, mitigating the Topological Naming Problem.
• Adhering to DRY - Don't Repeat Yourself.
• CAD modeling semantics mapped to object-oriented paradigm
  • Model parameters are mapped to __init__ args.
  • Model specification, simplification or parameter modification via subclassing.
  • Reference geometries and init parameters as attributes.
• Explicit semantics of the object on many levels:
  • Assembly assumes strict hierarchical assembly directed acyclic graph.
  • Reference geometry is present with each Thing and annotated with language-compatible docstrings.
  • Derived designs track the pedigree in object-oriented inheritance.
  • Thing parameters are annotated and assume meaning on their own.
  • Joints have extensible semantics with arbitrary joint transform parametrization.
• Cloning existing complex geometry with incrementally adjusted parameters.
• Safety checks all around not to accidentally mess things up.
• Modular exporting of all subcomponents to STL, MuJoCo files or assembly graphs.
• Visualization utilities to distinguish different subcomponents

The library may be seen as a distillation of conventions. Of course everyone may break this library easily by hacking the internals of provided classes. The library was developed using Pyright LSP. The build123things library goes well with CQ-editor fork. If CQ-editor won't render, try deleting ~/.config/CadQuery/CQ-editor.conf or sth like that. Or add current dir to PYTHONPATH.

Installation

So far, I do not know any better way than creating a new (mini)conda environment and installing it there. This library is not yet deployed in pip, the recommended way of installing is via the VCS pip support. Ordinary system-wide installation tended to fail. The library was developed with Python 3.11.4.

conda create -n build123things python=3.11.4
pip3 install git+https://github.com/comrob/build123things

Getting Started

First, if you do not know already, get familiar with build123d which is the backbone for defining geometries. The build123things is an overlay which manages the build123d geometries while providing other utilities. To start with your design, create a class with Thing as its superclass, e.g.,

class MyDesign (Thing):
    def __init__ (self, param_1:float=5):
        self.reference_geometry = build123d.Sphere(radius=param_1)
        self.result_geometry = build123d.Box(param_1, param_1, param_1)
    def result(self):
        return self.result_geometry

Here, we defined a cube design with a reference bounding sphere. Please, see examples provided with the library to learn about assemblies and more. Visualize the result via cq-editor. Export the designs using, e.g., python3 -m build123things.export.assembly_graph very_simple_car VerySimpleCar.

Scientific Publications

This library is a considered a supplementary material for a manuscript submitted for the The 2024 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2024). In case of acceptance, we will provide here a preferred bibtex record.