OCP-Tessellate

Tessellate OCP (Python bindings for OpenCascade) shapes into a JSON-friendly format suitable for three-cad-viewer and downstream tooling such as ocp_vscode.

It accepts geometry from CadQuery, build123d, and raw OCP TopoDS_* shapes, walks the structure, computes triangulations / discretized edges, and emits a hierarchical group of meshed instances.

Installation

pip install ocp-tessellate

Requires Python 3.10+ and OCP 7.8, 7.9 or 8.0.

Quick start

Programmatic pipeline

For embedding in a tool (the path used by ocp_vscode):

from build123d import Box, Sphere, Compound
from ocp_tessellate.convert import to_ocpgroup, tessellate_group

box = Box(1, 2, 3)
sphere = Sphere(0.5)
sphere.label = "ball"
assembly = Compound(label="root", children=[box, sphere])

# Step 1: convert to an OcpGroup hierarchy + instance list
group, instances = to_ocpgroup(assembly)

# Step 2: tessellate the instances
meshed_instances, shapes, mapping = tessellate_group(group, instances)
# `shapes` is a JSON-serializable tree consumable by three-cad-viewer

Direct export to three-cad-viewer

The simplest path — emit a .js file that a three-cad-viewer page can load directly:

from build123d import Box
from ocp_tessellate.convert import export_three_cad_viewer_js

box = Box(1, 2, 3)
export_three_cad_viewer_js("box", box, filename="box.js")
# writes box.js with `var box = {...}` ready for three-cad-viewer/examples

This is the bridge to three-cad-viewer: bundles tessellated instances + scene tree into a single JSON payload assigned to a JS variable.

Public API

Three entry points in ocp_tessellate.convert:

export_three_cad_viewer_js(var, *objs, names=None, colors=None, alphas=None, modes=None, filename=None, keep_instances=False) — runs the full pipeline (to_ocpgroup → tessellate_group → JSON encode) and writes a var <name> = {...}; JS file. The direct integration point with three-cad-viewer.
to_ocpgroup(*objs, names=None, colors=None, alphas=None, modes=None, ...) — converts CAD objects (build123d / CadQuery / OCP / nested dicts and lists) into an OcpGroup hierarchy plus an instance list. Accepts per-object names, colors, alphas, materials, modes ((state_faces, state_edges) 2-tuples), and a default_color. Renderer-control flags include helper_scale, render_joints, render_mates, show_parent, show_locals.
tessellate_group(group, instances, kwargs=None, progress=None, timeit=False) — meshes the instances and returns the structures consumed by three-cad-viewer. kwargs can carry tessellation parameters like deviation, angular_tolerance, edge_accuracy, and render_normals.

For lower-level use, OcpConverter exposes to_ocp(...), which is what to_ocpgroup calls internally.

What gets shown

Inputs are walked recursively. The resulting tree mirrors the input structure:

input	result
build123d / CadQuery / OCP shape	a single `OcpObject`
`dict`	a `Dict` group with one named child per key
`list` / `tuple`	a `List` group with default-named children
`ShapeList`	a `ShapeList` group exposing each item individually
`Compound(children=[...])` (assembly)	a group preserving the assembly hierarchy
`Compound(...)` (standard, no children)	unwrapped to its inner shape
`BuildPart` / `BuildSheet` / `BuildSketch` / `BuildLine`	a single `OcpObject` for the builder result, plus a `part_local` / `sheet_local` / `sketch_local` / `line_local` sibling unless disabled

Compatibility

Python 3.10+
OCP 7.8, 7.9 and 8.0
build123d (current)
CadQuery 2.x

License

Apache 2.0. See LICENSE.

Changelog

See CHANGELOG.md.

Metadata

Release files for ocp-tessellate 3.5.3

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for ocp-tessellate 3.5.3
File	Size	Uploaded
ocp_tessellate-3.5.3.tar.gz	88.3 kB	Sep 15, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for ocp-tessellate 3.5.3
File	Interpreter	ABI	Platform	Reset
ocp_tessellate-3.5.3-py3-none-any.whl 61.8 kB Sep 15, 2026	Python 3	none	any	Details

Total release size: 150.1 kB

Release files / ocp_tessellate-3.5.3.tar.gz

Download URL	ocp_tessellate-3.5.3.tar.gz
Size	88.3 kB
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Uploaded via	`twine/7.0.0 CPython/3.13.12`

Release files / ocp_tessellate-3.5.3-py3-none-any.whl

Download URL	ocp_tessellate-3.5.3-py3-none-any.whl
Size	61.8 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`411017293e42817904f54f30268dae94ac18b18f3beeba9c0d10fbc12a3d277f`
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Upload date	Sep 15, 2026
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Uploaded via	`twine/7.0.0 CPython/3.13.12`