Troubleshooting

May 12, 2026 · View on GitHub

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)