Files and viewer

Writing files

shape.export(path) picks the format from the extension; the functions below give more control. All of them accept a single shape or a list.

Format	Function	Contents
STEP (.step, .stp)	export_step	exact B-rep, names and colors
SMLib (.smb)	save	the kernel's native format, exact and lossless
glTF (.glb, .gltf)	export_glb, export_gltf	triangles, edges as lines, colors, names
STL (.stl)	export_stl	triangles
OBJ (.obj)	export_obj	triangles

from smlibpy import *

bracket = (Box(60, 40, 8) - Cylinder(4, 10)).named("bracket").colored("steelblue")
cover = Box(60, 40, 2).translate(0, 0, 10).named("cover").colored("#d9925a")

export_step([bracket, cover], "assembly.step")
export_step(bracket, "bracket_inch.step", unit="inch")
export_stl(bracket, "bracket.stl", tolerance=0.01)
export_glb([bracket, cover], "assembly.glb")
save(bracket, "bracket.smb")

STEP

The STEP writer produces AP214 files with the exact geometry: planes, cylinders, cones, spheres, tori, lines, circles and ellipses as analytic entities, everything else as (rational) B-splines with the kernel's own control points and knots. Solids become MANIFOLD_SOLID_BREPs, hollow solids BREP_WITH_VOIDS, sheets open shells. Part names and colors are kept. The output is checked in the test suite by reading it back with OpenCASCADE.

unit is the unit of the file: "mm" (default), "cm", "m", "um" or "inch". The model (in mm) is converted to it, so bracket_inch.step above holds a 2.362 x 1.575 x 0.315 inch part, which any CAD system (and import_step) reads as 60 x 40 x 8 mm.

Meshes

tolerance is the largest distance between mesh and true surface (default: 0.1 % of the part's size); angle limits the angle between neighbouring triangles on curved faces.

glTF is defined in meters: export_glb and export_gltf keep the positions in millimeters and scale the scene's root node by 0.001, so viewers that respect units show the part at its real size. STL and OBJ have no units and hold the millimeter values.

Reading files

load picks the format from the extension, the same way export does:

from smlibpy import *

Box(60, 40, 8).named("bracket").export("bracket.step")

bracket = load("bracket.step")   # exact, from any CAD system
print(bracket.name, bracket.volume)

STEP and SMLib's own .smb files give exact parts; an STL file gives a Mesh (import_stl).

STEP

import_step(path) reads the solids and surfaces of AP203, AP214 and AP242 files. A file with one body returns a Part, or a Shell if it is a surface model. A file with several returns a ShapeList with every body at its place in the assembly. Names and colors come along (an unnamed solid takes the name of its product), and lengths are converted to millimeters whatever unit the file uses.

Each face is rebuilt on the exact surface from the file and each edge on its exact curve: a cylinder stays a cylinder, and a NURBS surface keeps its control points and knots. Faces share their edges as they do in the file, so nothing is stitched together by tolerance. A body that still comes out invalid goes through the kernel's healer; valid bodies are left alone, and heal=False skips healing.

The importer is checked against OpenCASCADE on more than 400 files written by NX, CATIA, Creo, SolidWorks, Inventor, Onshape, FreeCAD, KiCad and ClassCAD, the CAx-IF test models among them. Not read yet: wireframe geometry, references to other files, PMI, and assembly placements that mirror a part.

Pictures

render draws shapes into a PNG without a browser or a graphics card, which suits scripts, CI jobs and documentation:

from smlibpy import *

part = Box(40, 30, 10) - Cylinder(6, 20)
render(part, path="part.png")                                 # isometric view
render(part, path="views.png", view="sheet", size=(1000, 760))  # ISO method E: front, left, top, iso

view takes a name ("iso", "front", "back", "left", "right", "top", "bottom"), a direction from the model towards the camera, or "sheet". Hidden edges stay hidden, and the seams of round faces are left out. The function returns the PNG bytes, so in a notebook IPython.display.Image(render(part)) shows it inline.

Viewer

show(bracket)
show(bracket, cover, Spline((0, 0, 40), (30, 20, 50), (60, 0, 40)))

show displays parts, sketches, surfaces, faces, edges, wires and meshes together. In a Jupyter notebook it renders inline; elsewhere it writes an HTML page and opens it in the browser. The page is self-contained apart from three.js, which it loads from a CDN: show(part, path="part.html", open_browser=False) keeps a copy to share.

In a notebook, a shape at the end of a cell shows itself.