ocp_viewer

The standalone OCP CAD viewer: a browser page and the server behind it.

Installation

pip install ocp_viewer

into the environment that also holds your CAD library (build123d or cadquery).

From a checkout — for local use with uv add path/to/ocp-viewer, uv pip install path/to/ocp-viewer or pip install path/to/ocp-viewer — run make assets in the checkout first. The page's JavaScript and stylesheet are copied in from npm and are not in git, so a package built from a checkout that never ran it ships without them; the server says so at start. make dist runs it for you.

Run

python -m ocp_viewer

and open the printed URL in a browser — http://127.0.0.1:3939 by default. Then show from any Python process in that environment:

from build123d import *
from ocp_viewer import *

show(Box(1, 2, 3))

— the same show you would use with the VS Code extension, pointed at this viewer.

Documentation

Everything else — settings, addressing several viewers, editors, Docker, the whole shared behavior — is in the documentation: the OCP Viewer chapter for this viewer's specifics, bernhard-42.github.io/ocp_viewer_docs for the rest.

What is here, and what is not

Almost nothing about viewing is here. The show pipeline, the config semantics, the render and camera policy, the tree state, the measurement backend, the splash logo, the port registry and the wire protocol are all ocp-viewer-core, shared with the VS Code extension, Jupyter CadQuery and build123d Studio. What is left is a websocket server that also hands out one page, and the settings that reach them.

That is the point of the split rather than a side effect of it. A camera that behaves differently here than in VS Code is a bug in one of them, and there is now one place to fix it.

Settings

Three sources, later winning over earlier:

1. the defaults in server/settings.py
2. ~/.ocpvscode_standalone, if it exists — write one with python -m ocp_viewer --create_configfile
3. the command line — python -m ocp_viewer --help

The file keeps its old name so that an existing one still works.

Development

make install      # editable
make assets       # copy the renderer and the core into static/
make check        # ruff check + ty check, and no formatter
make run

make assets copies JavaScript out of node_modules: three-cad-viewer and ocp-viewer-core are npm packages, installed from the registry. The copies under static/ are gitignored. After bumping either dependency, run make assets again so they follow.

Licence

Apache-2.0.