SwiftX

📖 Documentation: https://secondmouseau.github.io/SwiftX/

A small, native-Swift reader for DirectX .x model geometry — the legacy Microsoft retained-mode mesh format, still used by tools and simulators such as RailSim.

.x ships in four flavours, distinguished by the xof header: txt (text), bin (binary tokens), tzip (MSZip-compressed text), and bzip (MSZip-compressed binary). SwiftX reads all four (32- and 64-bit floats), extracting geometry only — vertices and triangle faces (polygons are fan-triangulated) across every Mesh in the file — and skipping templates, frames, normals, materials and textures.

• Pure Swift, no third-party dependencies.
• Validated against a 116-file RailSim corpus: geometry bbox-exact vs Assimp on every file.

Install

dependencies: [
    .package(url: "https://github.com/SecondMouseAU/SwiftX.git", from: "1.0.0"),
],
// target:
.target(name: "YourTarget", dependencies: [.product(name: "SwiftX", package: "SwiftX")]),

Use

import SwiftX

let mesh = try X.read(contentsOf: url)          // welded, degenerate faces dropped
print(mesh.vertexCount, mesh.triangleCount)

for t in 0..<mesh.triangleCount {
    let i = t * 3
    let a = mesh.positions[Int(mesh.indices[i])]
    // …
}

Everything is configurable via X.Options — weldEpsilon (seam welding; nil to keep raw indexing), dropDegenerate, scale, and flipZ (left-/right-handed). X.looksLikeX(data) sniffs the "xof " signature.

Scope & notes

SwiftX is a geometry reader: no rig/animation, materials, textures, or writing. The compressed flavours (tzip/bzip) use Apple's Compression framework for raw-DEFLATE; on platforms without it, compressed files throw X.Error.compressionUnavailable while text/binary .x still work. Multi-block MSZip (files >32 KB uncompressed) is a future addition — single-block (the vast majority of parts) is fully supported.

In simulators like RailSim, the .x files are individual parts and the assembly (which parts, how many, where placed) lives in separate text definition files. SwiftX reads the parts; the assembly is a separate concern.

License

MIT.