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Getting started

Install​

pip install smlibpy

There are wheels for Linux (x86_64, aarch64), macOS (arm64, x86_64) and Windows, for Python 3.10 to 3.14. Elsewhere pip builds the kernel from source, which needs CMake 3.20 or newer and a C++17 compiler (Xcode command line tools on macOS, build-essential on Linux, Visual Studio on Windows) and takes about a minute.

To work on smlibpy itself, clone it with its submodule, build in place and put src on the Python path:

git clone --recursive https://github.com/awv-informatik/smlibpy
cd smlibpy
cmake -S . -B build -G Ninja && cmake --build build
export PYTHONPATH=$PWD/src

Your first part​

Everything is in one namespace:

from smlibpy import *

A part starts from a primitive or from a sketch. Here a plate with rounded corners, four holes and a pocket:

plate = Box(80, 60, 10)                                  # centered on the origin
plate = plate.fillet(plate.edges().parallel_to(Z), 8)    # round the four vertical edges
plate -= GridLocations(60, 40, 2, 2) * Cylinder(4, 10)   # subtract four cylinders
pocket = Rectangle(30, 20).on(plate.faces().top())       # a sketch on the top face
plate -= pocket.extrude(-4)                              # extruded into the plate

Each line returns a new part; nothing is modified in place. plate -= tool is short for plate = plate - tool.

Look at it​

show(plate)

opens the part in your browser. In Jupyter, show(plate) (or just plate as the last expression of a cell) displays it inline. Drag to orbit, right-drag to pan, scroll to zoom, press F to frame the model.

Measure it​

print(plate.volume)          # 43040.0
print(plate.area)
print(plate.bbox().size)     # Vector(80, 60, 10)
print(plate.is_valid())      # a closed, manifold solid with a positive volume

Volumes, areas and centers come from exact integration over the NURBS geometry, not from a mesh.

Save it​

plate.export("plate.step")   # exact B-rep for any CAD system
plate.export("plate.stl")    # triangle mesh for 3D printing
plate.export("plate.glb")    # for the web, Blender, three.js

The file type follows the extension. See files and viewer for options.

Units and conventions​

  • Lengths are in millimeters unless you decide otherwise; STEP export can declare other units.
  • Angles are in degrees everywhere.
  • Z points up. The front view looks along +Y, so Plane.front faces -Y.
  • New shapes are centered on the origin; use align= to change that.

Next: concepts.