VS Code extension for viewing HepMC3 ASCII event files (.hepmc, .hepmc3).
Features
Opens HepMC files in a custom editor
Shows one event at a time with next/previous navigation
Supports pan and zoom
Right-click in the graph to save the current event as SVG
Layout and styling follow pyhepmc's graphviz view:
unicode particle names for every PDG ID pyhepmc knows (6,496 entries incl. nuclei)
track thickness scales with energy relative to the event's most energetic particle
color by category (hadron, quark/gluon, lepton/boson, generator-internal, …), dashed neutrals,
arrowheads on beam and final-state particles only
Shows particle hover tooltips with:
name
PDG ID
status
mass
4-momentum
electric charge
Supported input
The parser handles the common HepMC3 ASCII records used in this project:
E event headers
U units
W event weights
A attributes
P particles
V vertices
Architecture
src/common/ contains the portable HepMC parser, PDG lookup (pdg.ts + generated pdg-data.json),
graph construction, the DOT builder (dot.ts) and the graphviz WASM wrapper (render.ts).
src/webview/ contains the browser-side shell: it injects the SVG produced by the host and adds zoom and tooltips.
src/extension.ts contains the VS Code custom editor host layer; it parses the file, lays events out with
graphviz on request, and serves the theme stylesheet (src/common/theme.ts).
Vocabulary is in CONTEXT.md; design decisions are recorded in docs/adr/.
Build
npm install
npm run build
Regenerating particle data
src/common/pdg-data.json is generated from pyhepmc's unicode name table and the particle package.
It is committed, so a normal build needs no Python. To refresh it:
uv run --with "pyhepmc,particle" python scripts/generate_pdg_data.py
Notes
The UI is intentionally browser-native so it can be reused in a standalone website later
(@hpcc-js/wasm-graphviz runs in both Node and browsers).
d3-selection and d3-zoom are used for the lightweight interactive view layer.
Third-party notices
Particle names in src/common/pdg-data.json come from pyhepmc
(BSD-3-Clause), with categories and charges derived from particle
(BSD-3-Clause).
