build123d Compound -> MultiBlock

A build123d Compound with labelled children becomes a pyvista.MultiBlock whose block names match the child labels. Per-block cad.label and cad.color field data are preserved.

This example builds a real motor-mount-style assembly (a base plate, a bearing housing with a bore, and a shaft) with each part labelled to mirror a real engineering BOM (bill of materials).

import build123d as b3d
import pyvista as pv

import pyvista_cad

Build a labelled multi-part assembly.

base = b3d.Box(80.0, 50.0, 6.0, align=(b3d.Align.MIN, b3d.Align.MIN, b3d.Align.MIN))
base.label = 'base_plate'

housing = b3d.Pos(40.0, 25.0, 6.0) * b3d.Cylinder(
    radius=14.0,
    height=20.0,
    align=(b3d.Align.CENTER, b3d.Align.CENTER, b3d.Align.MIN),
) - b3d.Pos(40.0, 25.0, 6.0) * b3d.Cylinder(
    radius=9.0,
    height=22.0,
    align=(b3d.Align.CENTER, b3d.Align.CENTER, b3d.Align.MIN),
)
housing.label = 'bearing_housing'

shaft = b3d.Pos(40.0, 25.0, 16.0) * b3d.Cylinder(
    radius=8.0,
    height=50.0,
    align=(b3d.Align.CENTER, b3d.Align.CENTER, b3d.Align.CENTER),
    rotation=(90.0, 0.0, 0.0),
)
shaft.label = 'shaft'

compound = b3d.Compound(children=[base, housing, shaft])

Convert. Labels surface as MultiBlock keys.

mb = pyvista_cad.from_build123d(compound, linear_deflection=0.2)
mb

MultiBlock (0x7f6fa8111c60)
  N Blocks:   3
  X Bounds:   0.000e+00, 8.000e+01
  Y Bounds:   -7.105e-15, 5.000e+01
  Z Bounds:   0.000e+00, 2.600e+01

MultiBlock 3 blocks 33 KiB

Bounds⧉X [0.000e+00, 8.000e+01]Y [-7.105e-15, 5.000e+01]Z [0.000e+00, 2.600e+01]

• Blocks: (3)
  • base_platePolyData24 pts · 12 cells · 5 KiB
  • bearing_housingPolyData216 pts · 212 cells · 18 KiB
  • shaftPolyData106 pts · 100 cells · 10 KiB

Render each part CAD-style (analytic smooth-shaded faces with the model’s topological edges, no triangle-mesh noise) in its own color so the BOM structure reads. Passing the build123d parts straight to pl.cad.add routes through the per-face B-rep path; the tessellated mb above is the conversion result, not the render source.

colors = ['tan', 'steelblue', 'firebrick']
pl = pv.Plotter()
for part, color in zip(compound.children, colors):
    pl.cad.add(part, color=color)
pl.view_isometric()
pl.show()

Static Scene

Interactive Scene