PathView

A browser-based visual editor for PathSim and FastSim models.

PathView is a visual node editor for PathSim and FastSim models: drag-and-drop block diagrams, live simulation preview with interactive plots, and instant sharing. By default it runs entirely in the browser via Pyodide: nothing to install, nothing to license, nothing sent to a server.

Diagrams stay real PathSim models: what you edit visually is what runs in the engine, and what you share is a model your colleague can open in Python. Models convert to standalone scripts from the command line:

pip install pathview
pathview serve                  # local server with full Python backend
pathview convert model.pvm      # .pvm diagram -> standalone model.py

The local server mode runs models against any installed Python environment, including packages with native dependencies that Pyodide cannot load. The UI is SvelteKit with SvelteFlow for the node editor, CodeMirror for code cells, and Plotly for interactive results.

History

PathView began as a project at the MIT Plasma Science and Fusion Center: a way to build and inspect PathSim models visually. Starting in November 2025 I rewrote it on my own stack (SvelteKit, SvelteFlow, Pyodide), and we transferred it to the PathSim organization. Today it is hosted free for everyone at view.pathsim.org, with the pip-installable local server for models that need packages beyond what Pyodide can load.