csx

A pure Rust library for continuous-structure geometry and material modeling, compatible with CSXCAD and openEMS.

• Clean-room implementation (no CSXCAD/openEMS code was consulted), MIT licensed. Behaviour is derived from public documentation, the observable file format and black-box runs of CSXCAD.
• Zero runtime dependencies; XML support is an optional (default) feature.
• Edition 2024, MSRV 1.95.

Overview

• Geometric primitives: box, multi-box, sphere, spherical shell, cylinder, cylindrical shell, polygon, extruded polygon, revolved polygon, curve, wire, point, polyhedron (inline or STL/PLY file) and expression-defined regions, with transformations and Cartesian/cylindrical coordinates.
• Properties: materials (anisotropic, position-weighted), Drude/Lorentz and Debye dispersive materials, metals, conducting sheets, excitations, probes, field dumps, lumped elements.
• Parametric models: every value may be an expression over named parameters.
• Priority-based point queries (property_at, medium_at) and spatial index.
• Rectilinear grids with graded smoothing and automatic mesh generation from the geometry (mesh).
• Read/write CSXCAD and openEMS XML files, including typed FDTD settings (feature xml).
• Tessellation of primitives and STL/PLY/VTK export; STL/PLY import.
• Discretisation of materials, metals, excitations and lumped elements onto the FDTD grid (discretize).

Example

use csx::primitives::BoxShape;
use csx::properties::Material;
use csx::{ContinuousStructure, CoordSystem, Property, TypeMask, Vec3};

let mut model = ContinuousStructure::new();
let fr4 = model.add_property(Property::material("FR4", Material::new(4.3, 0.0)));
model.add_primitive(fr4, BoxShape::new([-10.0, -10.0, 0.0], [10.0, 10.0, 1.6])).unwrap();

// Write and read back a CSXCAD XML file (feature `xml`).
let xml = model.to_xml_string();
let model = ContinuousStructure::from_xml_str(&xml).unwrap();

let hit = model.property_at(Vec3::new(0.0, 0.0, 0.5), CoordSystem::Cartesian, TypeMask::ANY);
assert_eq!(hit.unwrap().property.name, "FR4");

More examples:

• cargo run --example info -- file.xml — summary of a CSXCAD/openEMS file
• cargo run --example patch_antenna -- out.xml [out.vtk] — build, mesh and write a parametric patch antenna
• cargo run --example export_vtk -- file.xml out_dir — VTK + STL export
• cargo run --release --example discretize -- file.xml — discretise onto the mesh and print statistics

Compatibility notes

Behaviour confirmed from public documentation, published XML output and black-box runs of CSXCAD 0.7 (its Python API, never its source):

• Coordinate systems: a Box in cylindrical coordinates is an annular sector; spheres, cylinders, their shells, curves, wires and points convert their defining points from (ρ, α, z); multi-boxes, polygons, extruded and revolved polygons and polyhedra are always Cartesian. Multi-boxes ignore their own CoordSystem and compare raw coordinates in the structure's system (no angle wrapping). Primitives without CoordSystem inherit the structure's; structure queries take coordinates in the structure's system. A cylindrical box compares cylindrical queries as given (negative ρ is outside, α modulo 2π); every other shape folds (-ρ, α) through the Cartesian conversion. Verified with 140k random cylindrical-structure queries. Known divergence: CSXCAD clips cylindrical wires to an inconsistently computed bounding box; csx keeps the true geometry.
• Curves and points never contain a point.
• Equal priorities: the earlier property wins.
• Transformations are applied in list order; angles are radians in files; Matrix is row-major acting on column vectors (translation in the last column); vector scaling is written Scale3.
• Polygon vertices (X1, X2) map to axes (n+1)%3, (n+2)%3 for normal n; revolved polygons rotate right-handed about RotAxisDir starting at the remaining (radial) axis.
• Material values are written as three comma separated values; with Isotropy="1" only the first is used. Dispersive terms use 1-based _n suffixes in Property and Weight.
• Weighting function variables: x y z rho a r t, in drawing units.
• Expressions: any non-zero value is true.
• UserDefined primitives are not supported by CSXCAD 0.7; csx reads and writes them in its own format (<Equation> text, <CoordShift> origin).

Features

License

MIT — see LICENSE.