@chitrashensah/geant4-csg

Geant4 solid geometries for Three.js — detector modeling for web-based particle physics simulations.

Installation

npm install three @chitrashensah/geant4-csg

Available Geometries

| Class | Geant4 Equivalent | Description | | ------------------ | ----------------- | --------------------------------- | | G4Box | G4Box | Rectangular box | | G4Tubs | G4Tubs | Cylindrical tube section | | G4Cons | G4Cons | Conical section | | G4Sphere | G4Sphere | Spherical sector | | G4Torus | G4Torus | Torus section | | G4Para | G4Para | Parallelepiped | | G4Trd | G4Trd | Trapezoid | | G4Trap | G4Trap | Generic trapezoid | | G4Trap4 | G4Trap (4-param) | Simple trapezoid | | G4Ellipsoid | G4Ellipsoid | Triaxial ellipsoid | | G4EllipticalTube | G4EllipticalTube | Elliptical tube | | G4EllipticalCone | G4EllipticalCone | Elliptical cone | | G4Hype | G4Hype | Hyperboloid | | G4Tet | G4Tet | Tetrahedron | | G4Polycone | G4Polycone | Multi-section solid of revolution | | G4Polyhedra | G4Polyhedra | Polygonal prism | | G4TwistedBox | G4TwistedBox | Twisted box | | G4TwistedTrd | G4TwistedTrd | Twisted trapezoid | | G4TwistedTrap | G4TwistedTrap | Twisted generic trapezoid | | G4TwistedTubs | G4TwistedTubs | Twisted tube |

Quick Start

import * as THREE from 'three';
import { G4Tubs, G4Sphere, G4Box } from '@chitrashensah/geant4-csg';

// Cylindrical tube: G4Tubs(name, rMin, rMax, halfZ, startPhi, deltaPhi)
const tube = new G4Tubs('myTube', 0.5, 1.0, 1.0, 0, 360);

// Sphere: G4Sphere(name, rMin, rMax, startPhi, deltaPhi, startTheta, deltaTheta)
const sphere = new G4Sphere('mySphere', 0, 1.0, 0, 360, 0, 180);

// Box: G4Box(name, halfX, halfY, halfZ)
const box = new G4Box('myBox', 1.0, 1.0, 1.0);

// All geometries extend THREE.BufferGeometry
const mesh = new THREE.Mesh(tube, new THREE.MeshStandardMaterial());
scene.add(mesh);

All dimensions are in centimeters. All angles are in degrees.

Scene Persistence with G4CSGLoader

By default, Three.js ObjectLoader does not know how to deserialize custom geometry types. Use G4CSGLoader to correctly save and reload scenes containing Geant4 geometries:

import { G4CSGLoader } from '@chitrashensah/geant4-csg';

// Replace THREE.ObjectLoader with G4CSGLoader when loading scenes
const loader = new G4CSGLoader();
const scene = await loader.parseAsync(json.scene);

G4CSGLoader extends THREE.ObjectLoader so it handles all standard Three.js objects identically — only custom Geant4 geometry types are handled differently.

Editor Integration

All geometries expose a static getEditorConfig() method for building parameter UIs dynamically:

import { getEditorConfig, GEOMETRY_CLASSES } from '@chitrashensah/geant4-csg';

// Get config for a specific geometry type
const config = getEditorConfig('G4Tubs', SetGeometryCommand);

// config.parameters — parameter definitions with labels, min, max, step, defaults
// config.validate   — validation function to enforce constraints
// config.createGeometry — factory function to build the geometry from params

JSON Serialization

All geometries support toJSON and fromJSON for scene serialization:

// Serialize
const json = geometry.toJSON();

// Deserialize
const geometry = G4Tubs.fromJSON(json);

Contributing

Contributions welcome. Please open an issue or pull request on GitHub.

License

MIT © Chitrashen Sah

Author

Chitrashen Sah — Research Assistant, Physics Department, University of South Dakota

Developed as part of the Geant4 Web Project — a web-based particle physics detector simulation platform built on Geant4 and Three.js.

Acknowledgments

• CSG Implementation — Based on THREE-CSGMesh by Sean Bradley (MIT License), derived from original work by Evan Wallace
• Dr. Jing Liu — Advisor, USD Physics Department
• Geant4 Collaboration
• Three.js Community