OCP CAD Viewer for VS Code

OCP CAD Viewer for VS Code is an extension to show CadQuery and build123d objects in VS Code via the three-cad-viewer viewer component.

Installation

Prerequisites

• A fairly recent version of Microsoft VS Code, e.g. 1.85.0 or newer
• The Python extension installed in VS Code
• Necessary tools:
  • python and pip available in the Python environment that will be used for CAD development. Note, even when you use another package manager, pip is needed internally and needs to be available.

Notes:

• To use OCP CAD Viewer, start VS Code from the commandline in the Python environment you want to use or select the right Python interpreter in VS Code first. OCP CAD Viewer depends on VS Code using the right Python interpreter (i.e. mamba / conda / pyenv / poetry / ... environment).
• For VSCodium, the extension is not available in the VS code market place. You need to download the the vsix file from the release folder and install it manually.

Installation

1. Open the VS Code Marketplace, and search and install OCP CAD Viewer 3.0.1.

   Afterwards the OCP viewer is available in the VS Code sidebar:

   

2. Clicking on it shows the OCP CAD Viewer UI with the viewer manager and the library manager:

   

   You have 3 options:

   • Prepare OCP CAD Viewer for working with build123d: Press the Quickstart build123d button.

     This will install OCP, build123d, ipykernel (jupyter_client), ocp_tessellate and ocp_vscode via pip

     

   • Prepare OCP CAD Viewer for working with CadQuery: Press the Quickstart CadQuery button.

     This will install OCP, CadQuery, ipykernel (jupyter_client), ocp_tessellate and ocp_vscode via pip

     

   • Ignore the quick starts and use the "Library Manager" to install the libraries via pip (per default, this can be changed in the VS Code settings). Install the needed library by pressing the down-arrow behind the library name (hover over the library name to see the button) in the "Library Manager" section of the OCP CAD Viewer sidebar. For more details, see here

   Quickstart will also

   • (optionally) install the the Jupyter extension for VS Code from Microsoft
   • start the OCP viewer
   • create a demo file in a temporary folder to quickly see a simple usage example

Notes:

• Do not use the OCP CAD Viewer logo to verify your OCP CAD Viewer settings! The logo overwrites all your settings in VS Code with its own settings to always look the same on each instance. Use a simple own model for checking your configuration

• If you run into issues, see Troubleshooting

Install Via CLI

If you aren't using VS Code, you can install/use this extension via command line

Since this is a python extension, it is recommended to install/activate a virtual environment first, (e.g. uv, venv. poetry, conda, pip, etc)

• uv based virtual environemnts:

  source .venv/bin/activate  # to activate the uv virtual environment
  uv add ocp-viewer
  

• pip for other virtual environments:

  source .venv/bin/activate  # to activate venv virtual environments
  conda / mamba / micromamba activate <env>  # to activate conda like virtual environments
  pip install ocp-viewer
  

Note: The extension is in pypi only pypi, so for conda, mamba or micromamba environments pip or uv pip needs to be used.

Migration from v2.9.0 to v3.0.X

• Change show parameter ticks to ticks/2

• For joints together with render_joints, instead of

  +- object_name
     +- shape
     +- joints
        +- joint1
        +- joint2
  

  you will find

  +- object_name
  +- object_name.joints
     +- joint1
     +- joint2
  

  Since joints are not under the object_name group, they do not automate automatically any more. Use the keyword animate_joints=True with add_track

• List with unviewable objects only are not shown as empty objects any more but ignored. So possibly less objects will be shown, and you might need to change how you access to these rendered objects.

Usage

Running code using Jupyter

• Start the OCP CAD Viewer by pressing the box-arrow button in the "Viewer Manager" section of the OCP CAD Viewer sidebar (hover over the ocp_vscode entry to see the button).
• Import ocp_vscode and the CAD library by using the paste button being the library names in the "Viewer Manager" section
• Use the usual Run menu to run the code

Debugging code with visual debugging

After each step, the debugger checks all variables in locals() for being CAD objects and displays them with their variable name. Note:

• Check that OCP:on is visible in the status bar
• It also shows planes, locations and axis, so name your contexts
• It remembers camera position and unselected variables in the tree
• during debugging, show and show_object are disabled. They interfere with the visual debugging

Library Manager

You can also use "Library Manager" in the OCP CAD Viewer sidebar to manage the Python libraries for build123d, cadquery, ipython and ocp_tessellate (Press the down-arrow when hovering over a library name to install/upgrade it)

Default pip config for Settings

  "OcpCadViewer.advanced.quickstartCommands": {
    "cadquery": ["{unset_conda} {python} -m pip install ocp_vscode=={ocp_vscode_version} cadquery"],
    "build123d": ["{python} -m pip install ocp_vscode=={ocp_vscode_version} build123d"]
  },
  "OcpCadViewer.advanced.installCommands": {
    "cadquery": ["{unset_conda} {python} -m pip install --upgrade cadquery"],
    "build123d": ["{python} -m pip install --upgrade build123d"],
    "ocp_vscode": ["{python} -m pip install --upgrade ocp_vscode=={ocp_vscode_version}"],
    "ocp_tessellate": ["{python} -m pip install --upgrade ocp_tessellate"],
    "ipykernel": ["{python} -m pip install --upgrade ipykernel"],
    "jupyter_console": ["{python} -m pip install --upgrade jupyter_console"]
  },

uv config for Settings

  "OcpCadViewer.advanced.quickstartCommands": {
    "cadquery": ["uv add -p {python} ocp_vscode=={ocp_vscode_version} cadquery"],
    "build123d": ["uv add -p {python} ocp_vscode=={ocp_vscode_version} build123d"]
  },
  "OcpCadViewer.advanced.installCommands": {
    "cadquery": ["uv add -p {python} --upgrade cadquery"],
    "build123d": ["uv add -p {python} --upgrade build123d"],
    "ocp_vscode": ["uv add -p {python} --upgrade ocp_vscode=={ocp_vscode_version}"],
    "ocp_tessellate": ["uv add -p {python} --upgrade ocp_tessellate"],
    "ipykernel": ["uv add -p {python} --upgrade ipykernel"],
    "jupyter_console": ["uv add -p {python} --upgrade jupyter_console"]
  }

Extra topics

• Quickstart experience on Windows
• Use Jupyter to execute code
• Debug code with visual debugging
• Measure mode
• Object selection mode
• Use the show command
• Use the show_object command
• Use the push_object and show_objects command
• Use the show_all command
• Use the set_viewer_config command
• Download examples for build123d or cadquery
• Use the build123d snippets

Standalone mode

Standalone mode allows to use OCP CAD Viewer without VS Code: python -m ocp_vscode. This will start a Flask server and the viewer can be reached under http://127.0.0.1:<port number> (per default http://127.0.0.1:3939). All client side feature of the VS Code variant (i.e. show* features) should be available (including measurement mode) except visual debugging (see above) which relies on VS Code.

Use python -m ocp_vscode --help to understand the command line args:

Usage: python -m ocp_vscode [OPTIONS]

Options:
  --create_configfile            Create the config file .ocpvscode_standalone in
                                 the home directory
  --host TEXT                    The host to start OCP CAD with
  --port INTEGER                 The port to start OCP CAD with
  --debug                        Show debugging information
  --timeit                       Show timing information
  --tree_width TEXT              OCP CAD Viewer navigation tree width
                                 (default: 240)
  --no_glass                     Do not use glass mode with transparent
                                 navigation tree
  --theme TEXT                   Use theme 'light' or 'dark' (default:
                                 'light')
  --no_tools                     Do not show toolbar
  --tree_width INTEGER           Width of the CAD navigation tree (default:
                                 240)
  --control TEXT                 Use control mode 'orbit'or 'trackball'
  --up TEXT                      Provides up direction, 'Z', 'Y' or 'L'
                                 (legacy) (default: Z)
  --rotate_speed INTEGER         Rotation speed (default: 1)
  --zoom_speed INTEGER           Zoom speed (default: 1)
  --pan_speed INTEGER            Pan speed (default: 1)
  --axes                         Show axes
  --axes0                        Show axes at the origin (0, 0, 0)
  --black_edges                  Show edges in black
  --grid_xy                      Show grid on XY plane
  --grid_yz                      Show grid on YZ plane
  --grid_xz                      Show grid on XZ plane
  --center_grid                  Show grid planes crossing at center of object
                                 or global origin(default: False)
  --collapse INTEGER             leaves: collapse all leaf nodes, all:
                                 collapse all nodes, none: expand all nodes,
                                 root: expand root only (default: leaves)
  --perspective                  Use perspective camera
  --ticks INTEGER                Default number of ticks (default: 5)
  --transparent                  Show objects transparent
  --default_opacity FLOAT        Default opacity for transparent objects
                                 (default: 0.5)
  --explode                      Turn explode mode on
  --angular_tolerance FLOAT      Angular tolerance for tessellation algorithm
                                 (default: 0.2)
  --deviation FLOAT              Deviation of for tessellation algorithm
                                 (default: 0.1)
  --default_color TEXT           Default shape color, CSS3 color names are
                                 allowed (default: #e8b024)
  --default_edgecolor TEXT       Default color of the edges of shapes, CSS3
                                 color names are allowed (default: #707070)
  --default_thickedgecolor TEXT  Default color of lines, CSS3 color names are
                                 allowed (default: MediumOrchid)
  --default_facecolor TEXT       Default color of faces, CSS3 color names are
                                 allowed (default: Violet)
  --default_vertexcolor TEXT     Default color of vertices, CSS3 color names
                                 are allowed (default: MediumOrchid)
  --ambient_intensity INTEGER    Intensity of ambient light (default: 1.00)
  --direct_intensity FLOAT       Intensity of direct light (default: 1.10)
  --metalness FLOAT              Metalness property of material (default:
                                 0.30)
  --roughness FLOAT              Roughness property of material (default:
                                 0.65)
  --help                         Show this message and exit.

Standalone mode with Docker

If you are not using vscode and you prefer to keep the standalone web viewer running separated in a container, then take a look at docker-vscode-ocp-cad-viewer.

Best practices

• Use the Jupyter extension for a more interactive experience. This allows to have one cell (separated by # %%) at the beginning to import all libraries

  # %%
  from build123d import *
  from ocp_vscode import *
  
  # %%
  b = Box(1,2,3)
  show(b)
  # %%

  and then only execute the code in the cell you are currently working on repeatedly.

• The config system of OCP CAD Viewer

  There are 3 levels:

  • Workspace configuration (part of the VS Code settings, you can access them e.g. via the gear symbol in OCP CAD Viewer's "Viewer Manager" when you hover over the label "VIEWER MANAGER" to see the button)
  • Defaults set with the command set_defaults per Python file
  • Parameters in show or show_object per command

  set_defaults overrides the Workspace settings and parameters in show and show_config override the other two.

  Note that not all parameters are available in the global Workspace config, since they don't make sense globally (e.g. helper_scale which depends on the size of the boundary box of the currently shown object)

  A common setup would be

  # %%
  from build123d import *
  import cadquery as cq
  
  from ocp_vscode import *
  set_port(3939)
  
  set_defaults(reset_camera=False, helper_scale=5)
  
  # %%
  ...

  Explanation

  • The first block imports build123d and CadQuery (omit what you are not interested in).
  • The second block imports all commands for OCP CAD Viewer. set_port is only needed when you have more than one viewer open and can be omitted for the first viewer)
  • The third block as an example sets helper_scale and reset_camera as defaults. Then every show_object or show command will respect it as the default

• Debugging build123d with show_all and the visual debugger

  • If you name your contexts (including Location contexts), the visual debugger will show the CAD objects assigned to the context.

  • Use show_all to show all cad objects in the current scope (locals()) of the Python interpreter (btw. the visual debugger uses show_all at each step)

    # %%
    from build123d import *
    set_defaults(helper_scale=1, transparent=True)
    
    with BuildPart() as bp:
        with PolarLocations(3,8) as locs:
            Box(1,1,1)
    
    show_all()
    # %%

    

• Keep camera orientation of an object with reset_camera

  Sometimes it is helpful to keep the orientation of an object across code changes. This is what reset_camera does:

  • reset_camera=Camera.Center will keep position and rotation, but ignore panning. This means the new object will be repositioned to the center (most robust approach)
  • reset_camera=Camera.KEEP will keep position, rotation and panning. However, panning can be problematic. When the next object to be shown is much larger or smaller and the object before was panned, it can happen that nothing is visible (the new object at the pan location is outside of the viewer frustum). OCP CAD Viewer checks whether the bounding box of an object is 2x smaller or larger than the one of the last shown object. If so, it falls back to Camera.CENTER. A notification is written to the OCP CAD Viewer output panel.
  • reset_camera=Camera.RESET will ensure that position, rotation and panning will be reset to the initial default

Development

Testing:

Native tessellator can be set via NATIVE_TESSELLATOR=1 and Python tessellator via NATIVE_TESSELLATOR=0.

When OCP_VSCODE_PYTEST=1 is set, show will not send the tessellated results to the viewer, but return it to the caller for inspection.

A full test cycle consist of:

NATIVE_TESSELLATOR=0 OCP_VSCODE_PYTEST=1 pytest -v -s pytests/
NATIVE_TESSELLATOR=1 OCP_VSCODE_PYTEST=1 pytest -v -s pytests/

Troubleshooting

• Generic ("it doesn't work")

  1. Confirm that VS Code extension and ocp_vscode have the same version. This can be seen in the OCP CAD Viewer UI. Or alternatively in the Output panel of VS Code:

     2025-07-06 14:51:33.418 [info ] extension.check_upgrade: ocp_vscode library version 2.8.6 matches extension version 2.8.6
     

  2. Test whether the standalone viewer works, see Standalone mode (to eliminate VS Code issues)

  3. Open a work folder and not a Python file (to ensure we do not get in Python path problems)

  4. Check the Output panel. Search for:

     • PythonPath: 'aaa/bbb/python' => right Python environment?
     • Server started on port xxxx (or so) => right port? default is 3939
     • Starting Websocket server => should not be followed by an error
     • OCP Cad Viewer port: xxxx, folder: yyyy zzzz => yyyy should be the right working folder?

  5. If all looks fine until now, then toggle Developer tools in VS Code and check browser console. Often we see a WebGL error for the browser of VS Code used for the viewer.

• CAD Models almost always are invisible in the OCP viewer window

  three-cad-viewer.esm.js:20276 THREE.WebGLProgram: Shader Error 0 - VALIDATE_STATUS false
  
  Material Name:
  Material Type: LineBasicMaterial
  
  Program Info Log: Program binary could not be loaded. Binary is not compatible with current driver/hardware combination. Driver build date Mar 19 2024. Please check build information of source that generated the binary.
  Location of variable pc_fragColor conflicts with another variable.

  VS Code internal browser that renders the viewer component uses a cache for code and other artifacts. This includes WebGL artifacts like compiled shaders. It can happen that e.g. due to a graphic driver update the compiled version in the cache does not fit to the new driver. Then this error message appears.

  Solution: Delete the VS Code browser cache on Linux (go to the section for your operating system)

Changes

3.0.1

Fixes

• Bring back explode tool and selection tool
• Ensure jupyter console can be launched when the path contains spaces

3.0.0

Features

• Viewer UI
  • The grids are now dynamic: Fonts rescale when zooming to keep them the same size and grid refines when zoom factor doubles (and vice versa)
  • Automatic theme switch (dark/bright) when theme of OS or browser is changed => NOTE: Unselect Ocp Cad Viewer > View:Dark in the VS Code settings!
  • The tick hint parameter now only refers to the positive axis and defaults to 5 (so overall it is still 10)
  • Help dialog can be closed by clicking outside on the canvas
• show command
  • reset_camera now supports Camera.ISO, Camera.TOP, Camera.BOTTOM, Camera.LEFT, Camera.RIGHT, Camera.FRONT, and Camera.BACK as new orientation defaults for the viewer (#189)
  • Joints are now shown with suffix .joints on the same level as the object they are attached to, in order to not change the overall assembly hierarchy needed for animation, (#138)
  • Animation of joints now needs to provide animate_joints parameter (in synch with render_joints)
  • Trim infinite axes and planes to 10 x helper_scale (#192)
  • helper_scale < 1.0 is treated as a relative scale: the absolute helper_scale will be calculated as the relative value times max bounding box size, i.e. helper_scales is a percentage of the max bounding box. For inifinite objects, helper_scale will be set to 1.0
  • Allow tree_width to be changed by each show command
  • List with unviewable objects only are not shown as empty objects any more but ignored
• Standalone
  • HTTP root redirect of http://localhost:8080 in standalone mode to show the viewer (no need of using http://localhost:8080/viewer any more)
• Library manager
  • The library manager will now install ocp_vscode~={ocp_vscode_version} per default, to simplifiy pure Python patch distribution (patch verions are compatible with the viewer). NOTE: Check your user/workspace settings.
  • Small restructuring of the Library Manager list (editable now is only visible when the package is editable, and then shows the project path)
  • Added cadquery_ocp to default install commands
• Support for pure uv environments without pip. The viewer now tries /env/path/to/python -m pip list for the library manager and if that fails it uses uv pip list -p /env/path/to/python. The install commands in the workspace settings need to change to use uv add -p {python}, see here #166
• Support for GDS chip design format
  • Add polygon renderer for GDS files
  • Add a z-scale tool for GDS files

Fixes

• Fix tree_width to be respected when no_glass is false (#194)
• Fix error when project path contains spaces, especially for pip list (#197)
• Add back default of 240 to standalone viewer call (#195, #196)
• Bump questionary to fix VSplit error
• Properly add alt key to keymap
• Change body element to respect the selected theme
• Fix new behavior of VS Code in status bar handling to ensure status bar is always visible
• Properly check ports vor IPv4 and IPv6 for standalone to avoid using the same port twice, once for IPv4 and once for IPv6
• three-cad-viewer
  • Change memory management to a new paradigm using a global function deepDispose which works recursively
  • Fix setCameraTarget
  • Fix keymapping regression where keymaps were not used any more