# cadrum

Rust CAD library powered by statically linked, headless [OpenCASCADE][occt] (OCCT 8.0.0).

[![GitHub License][license_img]][license_link]
[![Crates.io][crate_img]][crate_link]
[![docs.rs][docsrs_img]][docsrs_link]

<div align="center"><img src="https://lzpel.github.io/cadrum/00_chijin.png" alt="cadrum" height="300" width="auto"/></div>

<!--GALLERY-->

<table>
<tr><th width='25%'><a href='#primitives'>primitives</a></th><th width='25%'><a href='#write-read'>write read</a></th><th width='25%'><a href='#transform'>transform</a></th><th width='25%'><a href='#boolean'>boolean</a></th></tr>
<tr><td width='25%'><a href='#primitives'><img src='https://lzpel.github.io/cadrum/01_primitives.png' width='100%' height='auto' alt='primitives'/></a></td><td width='25%'><a href='#write-read'><img src='https://lzpel.github.io/cadrum/02_write_read.png' width='100%' height='auto' alt='write read'/></a></td><td width='25%'><a href='#transform'><img src='https://lzpel.github.io/cadrum/03_transform.png' width='100%' height='auto' alt='transform'/></a></td><td width='25%'><a href='#boolean'><img src='https://lzpel.github.io/cadrum/04_boolean.png' width='100%' height='auto' alt='boolean'/></a></td></tr>
<tr><th width='25%'><a href='#extrude'>extrude</a></th><th width='25%'><a href='#loft'>loft</a></th><th width='25%'><a href='#sweep'>sweep</a></th><th width='25%'><a href='#shell'>shell</a></th></tr>
<tr><td width='25%'><a href='#extrude'><img src='https://lzpel.github.io/cadrum/05_extrude.png' width='100%' height='auto' alt='extrude'/></a></td><td width='25%'><a href='#loft'><img src='https://lzpel.github.io/cadrum/06_loft.png' width='100%' height='auto' alt='loft'/></a></td><td width='25%'><a href='#sweep'><img src='https://lzpel.github.io/cadrum/07_sweep.png' width='100%' height='auto' alt='sweep'/></a></td><td width='25%'><a href='#shell'><img src='https://lzpel.github.io/cadrum/08_shell.png' width='100%' height='auto' alt='shell'/></a></td></tr>
<tr><th width='25%'><a href='#bspline'>bspline</a></th><th width='25%'><a href='#fillet'>fillet</a></th><th width='25%'><a href='#chamfer'>chamfer</a></th><th width='25%'><a href='#multiview'>multiview</a></th></tr>
<tr><td width='25%'><a href='#bspline'><img src='https://lzpel.github.io/cadrum/09_bspline.png' width='100%' height='auto' alt='bspline'/></a></td><td width='25%'><a href='#fillet'><img src='https://lzpel.github.io/cadrum/10_fillet.png' width='100%' height='auto' alt='fillet'/></a></td><td width='25%'><a href='#chamfer'><img src='https://lzpel.github.io/cadrum/11_chamfer.png' width='100%' height='auto' alt='chamfer'/></a></td><td width='25%'><a href='#multiview'><img src='https://lzpel.github.io/cadrum/12_multiview.png' width='100%' height='auto' alt='multiview'/></a></td></tr>
</table>

## Summary

Other Rust CAD bindings either require the user to install OCCT ahead of time
(with all the version skew this entails on Linux distros and Windows) or
expose OCCT's class hierarchy 1:1, where building a cube ends up touching
`gp_Pnt`, `gp_Ax2`, `BRepPrimAPI_MakeBox`, and `TopoDS_Shape` before any
geometry actually appears.

`cadrum` takes a different bet:

- **Static linking with prebuilt binaries.** `cargo build` on a supported
  target downloads a self-contained OCCT 8.0.0 tarball and links it
  statically. No system OCCT, no dynamic libraries to ship, no
  `LD_LIBRARY_PATH` in production.
- **A minimal type surface.** Three concrete shape types — `Solid`, `Edge`,
  `Face` — plus a triangle `Mesh` for visual output and `glam` vectors for
  input. Operations are inherent methods on the shape types, so
  `Solid::cube(...).rotate_z(0.5).translate(DVec3::X * 10.0)` chains like
  any value-returning Rust API.
- **Collections are first-class.** `Vec<Solid>` and `[Solid; N]` carry the
  same transform, query, and boolean methods as a single `Solid` via the
  `Compound` trait; the wire / edge-list pair has the parallel `Wire`
  trait.

## Introduction

OpenCASCADE represents shapes as a *boundary representation* (BRep): a solid
is a topological assembly of faces, faces are trimmed surfaces bounded by
edges, edges are 3D curves with a parameter range. Booleans, fillets,
sweeps, and the like rebuild this assembly under the hood; CAD I/O formats
like STEP / IGES preserve it exactly across applications.

Working at that level pays off when the application needs to reason about
geometry — closest-point queries, swept profiles along arbitrary spines,
history-tracked face derivation through booleans — and not merely render
triangles. Triangle meshes are a separate, lossy projection that `cadrum`
exposes through `Solid::mesh` when an STL export or SVG render is required.

## Capabilities

| Area | Methods |
|---|---|
| **Primitives** | `Solid::cube`, `Solid::sphere`, `Solid::cylinder`, `Solid::cone`, `Solid::torus`, `Solid::half_space` |
| **Curves** | `Edge::line`, `Edge::arc_3pts`, `Edge::circle`, `Edge::polygon`, `Edge::helix`, `Edge::bspline` |
| **Surfacing** | `Solid::extrude`, `Solid::sweep`, `Solid::loft`, `Solid::bspline` |
| **Editing** | `Solid::shell`, `Solid::fillet_edges`, `Solid::chamfer_edges`, `Solid::clean` |
| **Booleans** | `Solid::boolean_union`, `Solid::boolean_subtract`, `Solid::boolean_intersect` |
| **Transforms** *(shared by `Solid` / `Edge` / `Compound` / `Wire`)* | `translate`, `rotate`, `rotate_x` / `_y` / `_z`, `scale`, `mirror`, `align_x` / `_y` / `_z` |
| **Queries** | `Solid::volume`, `Solid::area`, `Solid::center`, `Solid::inertia`, `Solid::bounding_box`, `Solid::contains` |
| **Topology** | `Solid::iter_face`, `Solid::iter_edge`, `Face::iter_edge`, `Face::project`, `Edge::project` |
| **Identity / history** | `Solid::id`, `Face::id`, `Edge::id`, `Solid::iter_history` |
| **I/O** | `Solid::read_step` / `Solid::write_step`, `Solid::read_brep_binary` / `Solid::write_brep_binary`, `Solid::read_brep_text` / `Solid::write_brep_text` |
| **Mesh** | `Solid::mesh` → `Mesh`, `Mesh::write_stl`, `Mesh::write_svg` |
| **Color** *(feature `color`)* | per-face color preserved across STEP / BRep / STL / SVG round-trips |

## Build

Add this to your `Cargo.toml`:

```toml
[dependencies]
cadrum = "^0.7"
```

`cargo build` automatically downloads a prebuilt OCCT 8.0.0 binary for the targets below.

| | Target | Prebuilt |
|--|--------|----------|
| <img src="figure/linux.svg" width="16"> | `x86_64-unknown-linux-gnu` | ✅ |
| <img src="figure/linux.svg" width="16"> | `aarch64-unknown-linux-gnu` | ✅ |
| <img src="figure/windows.svg" width="16"> | `x86_64-pc-windows-msvc` | ✅ |
| <img src="figure/windows.svg" width="16"> | `x86_64-pc-windows-gnu` | ✅ |

For other targets, build OCCT from source:

```sh
OCCT_ROOT=/path/to/occt cargo build --features source-build
```

If `OCCT_ROOT` is not set, built binaries are cached under `target/`.

#### Requirements when building OpenCASCADE from source

- C++17 compiler (GCC, Clang, or MSVC)
- CMake

## Examples

#### Primitives

Primitive solids: box, cylinder, sphere, cone, torus — colored and exported as STEP + SVG.

```sh
cargo run --example 01_primitives
```

```rust,no_run
//! Primitive solids: box, cylinder, sphere, cone, torus — colored and exported as STEP + SVG.

use cadrum::{DVec3, Solid};

fn main() -> Result<(), cadrum::Error> {
    let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

    let solids = [
        Solid::cube(10.0, 20.0, 30.0)
            .color("#4a90d9"),
        Solid::cylinder(8.0, DVec3::Z, 30.0)
            .translate(DVec3::X * 30.0)
            .color("#e67e22"),
        Solid::sphere(8.0)
            .translate(DVec3::X * 60.0 + DVec3::Z * 15.0)
            .color("#2ecc71"),
        Solid::cone(8.0, 0.0, DVec3::Z, 30.0)
            .translate(DVec3::X * 90.0)
            .color("#e74c3c"),
        Solid::torus(12.0, 4.0, DVec3::Z)
            .translate(DVec3::X * 130.0 + DVec3::Z * 15.0)
            .color("#9b59b6"),
    ];

    Solid::write_step(&solids, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

    let scene = Solid::mesh(&solids, 0.5)?.scene(DVec3::ONE, DVec3::Z, true, false);
    scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
    scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

    println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
    Ok(())
}

```
- [01_primitives.png](https://lzpel.github.io/cadrum/01_primitives.png)
- [01_primitives.step](https://lzpel.github.io/cadrum/01_primitives.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/01_primitives.svg" alt="01_primitives" width="360"/>
</p>

#### Write read

Read and write: chain STEP, BRep text, and BRep binary round-trips with progressive rotation.

```sh
cargo run --example 02_write_read
```

```rust,no_run
//! Read and write: chain STEP, BRep text, and BRep binary round-trips with progressive rotation.

use cadrum::{Compound, DVec3, Solid};
use std::f64::consts::FRAC_PI_8;

fn main() -> Result<(), cadrum::Error> {
    let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();
    let step_path = format!("{example_name}.step");
    let text_path = format!("{example_name}_text.brep");
    let brep_path = format!("{example_name}.brep");

    // 0. Original: read colored_box.step
    let manifest_dir = env!("CARGO_MANIFEST_DIR");
    let original = Solid::read_step(
        &mut std::fs::File::open(format!("{manifest_dir}/steps/colored_box.step")).expect("open file"),
    )?;

    // 1. STEP round-trip: rotate 30° → write → read
    let a_written = original.clone().rotate_x(FRAC_PI_8);
    Solid::write_step(&a_written, &mut std::fs::File::create(&step_path).expect("create file"))?;
    let a = Solid::read_step(&mut std::fs::File::open(&step_path).expect("open file"))?;

    // 2. BRep text round-trip: rotate another 30° → write → read
    let b_written = a.clone().rotate_x(FRAC_PI_8);
    Solid::write_brep_text(&b_written, &mut std::fs::File::create(&text_path).expect("create file"))?;
    let b = Solid::read_brep_text(&mut std::fs::File::open(&text_path).expect("open file"))?;

    // 3. BRep binary round-trip: rotate another 30° → write → read
    let c_written = b.clone().rotate_x(FRAC_PI_8);
    Solid::write_brep_binary(&c_written, &mut std::fs::File::create(&brep_path).expect("create file"))?;
    let c = Solid::read_brep_binary(&mut std::fs::File::open(&brep_path).expect("open file"))?;

    // 4. Arrange side by side and export SVG + STL
    let [min, max] = original[0].bounding_box();
    let spacing = (max - min).length() * 1.5;
    let all: Vec<Solid> = [original, a, b, c].into_iter()
        .enumerate()
        .flat_map(|(i, solids)| solids.translate(DVec3::X * spacing * i as f64))
        .collect();

    let scene = Solid::mesh(&all, 0.5)?.scene(DVec3::new(1.0, 1.0, 2.0), DVec3::Z, true, false);
    scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
    scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

    Solid::mesh(&all, 0.1)?.write_stl(&mut std::fs::File::create(format!("{example_name}.stl")).unwrap())?;

    // 5. Print summary
    let stl_path = format!("{example_name}.stl");
    for (label, path) in [("STEP", &step_path), ("BRep text", &text_path), ("BRep binary", &brep_path), ("STL", &stl_path)] {
        let size = std::fs::metadata(path).map(|m| m.len()).unwrap_or(0);
        println!("{label:12} {path:30} {size:>8} bytes");
    }

    Ok(())
}

```
- [02_write_read.brep](https://lzpel.github.io/cadrum/02_write_read.brep)
- [02_write_read.png](https://lzpel.github.io/cadrum/02_write_read.png)
- [02_write_read.step](https://lzpel.github.io/cadrum/02_write_read.step)
- [02_write_read.stl](https://lzpel.github.io/cadrum/02_write_read.stl)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/02_write_read.svg" alt="02_write_read" width="360"/>
</p>
- [02_write_read_text.brep](https://lzpel.github.io/cadrum/02_write_read_text.brep)

#### Transform

Transform operations: translate, rotate, scale, and mirror applied to a cone.

```sh
cargo run --example 03_transform
```

```rust,no_run
//! Transform operations: translate, rotate, scale, and mirror applied to a cone.

use cadrum::{DVec3, Solid};
use std::f64::consts::PI;

fn main() -> Result<(), cadrum::Error> {
    let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

    let base = Solid::cone(8.0, 0.0, DVec3::Z, 20.0)
        .color("#888888");

    let solids = [
        // original — reference, no transform
        base.clone(),
        // translate — shift +20 along Z
        base.clone()
            .color("#4a90d9")
            .translate(DVec3::X * 40.0 + DVec3::Z * 20.0),
        // rotate — 90° around X axis so the cone tips toward Y
        base.clone()
            .color("#e67e22")
            .rotate_x(PI / 2.0)
            .translate(DVec3::X * 80.0),
        // scaled — 1.5x from its local origin
        base.clone()
            .color("#2ecc71")
            .scale(DVec3::ZERO, 1.5)
            .translate(DVec3::X * 120.0),
        // mirror — flip across Z=0 plane so the tip points down
        base.clone()
            .color("#e74c3c")
            .mirror(DVec3::ZERO, DVec3::Z)
            .translate(DVec3::X * 160.0),
    ];

    Solid::write_step(&solids, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

    let scene = Solid::mesh(&solids, 0.5)?.scene(DVec3::ONE, DVec3::Z, true, false);
    scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
    scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

    println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
    Ok(())
}

```
- [03_transform.png](https://lzpel.github.io/cadrum/03_transform.png)
- [03_transform.step](https://lzpel.github.io/cadrum/03_transform.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/03_transform.svg" alt="03_transform" width="360"/>
</p>

#### Boolean

Boolean operations: union, subtract, and intersect between a box and a cylinder.

```sh
cargo run --example 04_boolean
```

```rust,no_run
//! Boolean operations: union, subtract, and intersect between a box and a cylinder.

use cadrum::{DVec3, Solid};

fn main() -> Result<(), cadrum::Error> {
    let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

    let make_box = Solid::cube(20.0, 20.0, 20.0)
        .translate(DVec3::X * -10.+ DVec3:: Y*-10.)
        .color("#4a90d9");
    let make_cyl = Solid::cylinder(8.0, DVec3::Z, 30.0)
        .translate(DVec3::Z*-5.)
        .color("#e67e22");

    // union: merge both shapes into one — offset X=0
    let union = (&make_box + &make_cyl)?;

    // subtract: box minus cylinder — offset X=40
    let subtract = (&make_box - &make_cyl)?;

    // intersect: only the overlapping volume — offset X=80
    let intersect = (&make_box * &make_cyl)?;

    let cylinder = Solid::cylinder(8.0, DVec3::Z, 30.0)
        .translate(DVec3::X*4.);
    let [cylinder0, cylinder1, cylinder2] = [cylinder.clone(), cylinder.clone().rotate_z(std::f64::consts::TAU/3.), cylinder.clone().rotate_z(-std::f64::consts::TAU/3.)];

    // sum = union of all cylinders
    let sum = [&cylinder0, &cylinder1, &cylinder2].into_iter().sum::<Result<Solid, _>>()?.color("#d875ff");
    
    // product = intersection of all cylinders
    let product = [&cylinder0, &cylinder1, &cylinder2].into_iter().product::<Result<Solid, _>>()?.color("#00ff22");

    let shapes = [
        union.translate(DVec3::X * 0.0), 
        subtract.translate(DVec3::X * 40.0), 
        intersect.translate(DVec3::X * 80.0), 
        sum.translate(DVec3::X * 20.0 + DVec3::Y * 40.0), 
        product.translate(DVec3::X * 60.0 + DVec3::Y * 40.0)
    ];

    Solid::write_step(&shapes, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

    let scene = Solid::mesh(&shapes, 0.5)?.scene(DVec3::new(1.0, 1.0, 2.0), DVec3::Z, true, false);
    scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
    scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

    println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
    Ok(())
}

```
- [04_boolean.png](https://lzpel.github.io/cadrum/04_boolean.png)
- [04_boolean.step](https://lzpel.github.io/cadrum/04_boolean.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/04_boolean.svg" alt="04_boolean" width="360"/>
</p>

#### Extrude

Demo of `Solid::extrude`: push a closed 2D profile along a direction vector.

```sh
cargo run --example 05_extrude
```

```rust,no_run
//! Demo of `Solid::extrude`: push a closed 2D profile along a direction vector.
//!
//! - **Box**: square polygon extruded along Z
//! - **Oblique cylinder**: circle extruded at a steep angle
//! - **L-beam**: L-shaped polygon extruded along Z
//! - **Heart**: BSpline heart-shaped profile extruded along Z

use cadrum::{BSplineEnd, DVec3, Edge, Error, Solid};

/// Square polygon → box (simplest extrude).
fn build_box() -> Result<Solid, Error> {
	let profile = Edge::polygon(&[
		DVec3::new(0.0, 0.0, 0.0),
		DVec3::new(5.0, 0.0, 0.0),
		DVec3::new(5.0, 5.0, 0.0),
		DVec3::new(0.0, 5.0, 0.0),
	])?;
	Solid::extrude(&profile, DVec3::Z * 8.0)
}

/// Circle extruded at a steep angle → oblique cylinder.
fn build_oblique_cylinder() -> Result<Solid, Error> {
	let profile = [Edge::circle(3.0, DVec3::Z)?];
	Solid::extrude(&profile, DVec3::new(-4.0, -6.0, 8.0))
}

/// L-shaped polygon → L-beam.
fn build_l_beam() -> Result<Solid, Error> {
	let profile = Edge::polygon(&[
		DVec3::new(0.0, 0.0, 0.0),
		DVec3::new(4.0, 0.0, 0.0),
		DVec3::new(4.0, 1.0, 0.0),
		DVec3::new(1.0, 1.0, 0.0),
		DVec3::new(1.0, 3.0, 0.0),
		DVec3::new(0.0, 3.0, 0.0),
	])?;
	Solid::extrude(&profile, DVec3::Z * 12.0)
}

/// Heart-shaped BSpline profile extruded along Z.
fn build_heart() -> Result<Solid, Error> {
	let profile = [Edge::bspline(
		&[
			DVec3::new(0.0, -4.0, 0.0),   // bottom tip
			DVec3::new(2.0, -1.5, 0.0),
			DVec3::new(4.0, 1.5, 0.0),
			DVec3::new(2.5, 3.5, 0.0),    // right lobe top
			DVec3::new(0.0, 2.0, 0.0),    // center dip
			DVec3::new(-2.5, 3.5, 0.0),   // left lobe top
			DVec3::new(-4.0, 1.5, 0.0),
			DVec3::new(-2.0, -1.5, 0.0),
		],
		BSplineEnd::Periodic,
	)?];
	Solid::extrude(&profile, DVec3::Z * 7.0)
}

fn main() -> Result<(), Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let box_solid = build_box()?.color("#b0d4f1");
	let oblique = build_oblique_cylinder()?.color("#f1c8b0").translate(DVec3::X * 10.0);
	let l_beam = build_l_beam()?.color("#b0f1c8").translate(DVec3::X * 20.0);
	let heart = build_heart()?.color("#f1b0b0").translate(DVec3::X * 30.0);

	let result = [box_solid, oblique, l_beam, heart];

	Solid::write_step(&result, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	let scene = Solid::mesh(&result, 0.5)?.scene(DVec3::ONE, DVec3::Z, true, false);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
	Ok(())
}

```
- [05_extrude.png](https://lzpel.github.io/cadrum/05_extrude.png)
- [05_extrude.step](https://lzpel.github.io/cadrum/05_extrude.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/05_extrude.svg" alt="05_extrude" width="360"/>
</p>

#### Loft

Demo of `Solid::loft`: skin a smooth solid through cross-section wires.

```sh
cargo run --example 06_loft
```

```rust,no_run
//! Demo of `Solid::loft`: skin a smooth solid through cross-section wires.
//!
//! - **Frustum**: two circles of different radii → truncated cone (minimal loft)
//! - **Morph**: square polygon → circle (cross-section shape transition)
//! - **Tilted**: three non-parallel circular sections → twisted loft

use cadrum::{DVec3, Edge, Error, Solid};

/// Two circles → frustum (minimal loft example).
fn build_frustum() -> Result<Solid, Error> {
	let lower = [Edge::circle(3.0, DVec3::Z)?];
	let upper = [Edge::circle(1.5, DVec3::Z)?.translate(DVec3::Z * 8.0)];
	Ok(Solid::loft(&[lower, upper])?.color("#cd853f"))
}

/// Square polygon → circle (2-section morph loft).
fn build_morph() -> Result<Solid, Error> {
	let r = 2.5;
	let square = Edge::polygon(&[
		DVec3::new(-r, -r, 0.0),
		DVec3::new(r, -r, 0.0),
		DVec3::new(r, r, 0.0),
		DVec3::new(-r, r, 0.0),
	])?;
	let circle = Edge::circle(r, DVec3::Z)?.translate(DVec3::Z * 10.0);

	Ok(Solid::loft([square.as_slice(), std::slice::from_ref(&circle)])?.color("#808000"))
}

/// Three non-parallel circular sections → twisted loft.
fn build_tilted() -> Result<Solid, Error> {
	let bottom = [Edge::circle(2.5, DVec3::Z)?];
	let mid = [Edge::circle(2.0, DVec3::new(0.3, 0.0, 1.0).normalize())?
		.translate(DVec3::X + DVec3::Z * 5.0)];
	let top = [Edge::circle(1.5, DVec3::new(-0.2, 0.3, 1.0).normalize())?
		.translate(DVec3::new(-0.5, 1.0, 10.0))];

	Ok(Solid::loft(&[bottom, mid, top])?.color("#4682b4"))
}

fn main() -> Result<(), Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let frustum = build_frustum()?;
	let morph = build_morph()?.translate(DVec3::X * 10.0);
	let tilted = build_tilted()?.translate(DVec3::X * 20.0);

	let result = [frustum, morph, tilted];

	Solid::write_step(&result, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	let scene = Solid::mesh(&result, 0.5)?.scene(DVec3::ONE, DVec3::Z, true, false);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
	Ok(())
}

```
- [06_loft.png](https://lzpel.github.io/cadrum/06_loft.png)
- [06_loft.step](https://lzpel.github.io/cadrum/06_loft.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/06_loft.svg" alt="06_loft" width="360"/>
</p>

#### Sweep

Sweep showcase: M2 screw (helix spine) + U-shaped pipe (line+arc+line spine)

```sh
cargo run --example 07_sweep
```

```rust,no_run
//! Sweep showcase: M2 screw (helix spine) + U-shaped pipe (line+arc+line spine)
//! + twisted ribbon (`Auxiliary` aux-spine mode).
//!
//! `ProfileOrient` controls how the profile is oriented as it travels along the spine:
//!
//! - `Fixed`: profile is parallel-transported without rotating. Cross-sections
//!   stay parallel to the starting orientation. Suited for straight extrusions;
//!   on a curved spine the profile drifts off the tangent and the result breaks.
//! - `Torsion`: profile follows the spine's principal normal (raw Frenet–Serret
//!   frame). Suited for constant-curvature/torsion curves like helices and for
//!   3D free curves where the natural twist should carry into the profile.
//!   Fails near inflection points where the principal normal flips.
//! - `Up(axis)`: profile keeps `axis` as its binormal — at every point the
//!   profile is rotated around the tangent so one in-plane axis stays in the
//!   tangent–`axis` plane. Suited for roads/rails/pipes that must preserve a
//!   gravity direction. On a helix, `Up(helix_axis)` is equivalent to `Torsion`.
//!   Fails when the tangent becomes parallel to `axis`.
//! - `Auxiliary(aux_spine)`: profile's tracked axis points from the main spine
//!   toward a parallel auxiliary spine. Arbitrary twist control — e.g. a
//!   helical `aux_spine` on a straight `spine` produces a twisted ribbon.

use cadrum::{DVec3, Edge, Error, ProfileOrient, Solid, Wire};

// ==================== Component 1: M2 ISO screw ====================

fn build_m2_screw() -> Result<Solid, Error> {
	let r = 1.0;
	let h_pitch = 0.4;
	let h_thread = 6.0;
	let r_head = 1.75;
	let h_head = 1.3;
	// ISO M thread fundamental triangle height: H = √3/2 · P (sharp 60° triangle).
	let r_delta = 3f64.sqrt() / 2.0 * h_pitch;

	// Helix spine at the root radius. x_ref=+X anchors the start at (r-r_delta, 0, 0).
	let helix = Edge::helix(r - r_delta, h_pitch, h_thread, DVec3::Z, DVec3::X)?;

	// Closed triangular profile in local coords (x: radial, y: along helix tangent).
	let profile = Edge::polygon(&[DVec3::new(0.0, -h_pitch / 2.0, 0.0), DVec3::new(r_delta, 0.0, 0.0), DVec3::new(0.0, h_pitch / 2.0, 0.0)])?;

	// Align profile +Z with the helix start tangent, then translate to the start point.
	let profile = profile.align_z(helix.start_tangent(), helix.start_point()).translate(helix.start_point());

	// Sweep along the helix. Up(+Z) ≡ Torsion for a helix and yields a correct thread.
	let thread = Solid::sweep(&profile, &[helix], ProfileOrient::Up(DVec3::Z))?;

	// Reconstruct the ISO 68-1 basic profile (trapezoid) from the sharp triangle:
	//   union(shaft) fills the bottom H/4 → P/4-wide flat at the root
	//   intersect(crest) trims the top H/8 → P/8-wide flat at the crest
	let shaft = Solid::cylinder(r - r_delta * 6.0 / 8.0, DVec3::Z, h_thread);
	let crest = Solid::cylinder(r - r_delta / 8.0, DVec3::Z, h_thread);
	let thread_shaft = (&(&thread + &shaft)? * &crest)?;

	// Stack the flat head on top. Screw ends up centered on the origin.
	let head = Solid::cylinder(r_head, DVec3::Z, h_head).translate(DVec3::Z * h_thread);
	Ok((&thread_shaft + &head)?.color("red"))
}

// ==================== Component 2: U-shaped pipe ====================

fn build_u_pipe() -> Result<Solid, Error> {
	let pipe_radius = 0.4;
	let leg_length = 6.0;
	let gap = 3.0;
	let half_gap = gap / 2.0;
	let bend_radius = half_gap;

	// U-shaped path in the XZ plane, centered on origin in X: A↑B ⌒ C↓D.
	let a = DVec3::new(-half_gap, 0.0, 0.0);
	let b = DVec3::new(-half_gap, 0.0, leg_length);
	let arc_mid = DVec3::new(0.0, 0.0, leg_length + bend_radius);
	let c = DVec3::new(half_gap, 0.0, leg_length);
	let d = DVec3::new(half_gap, 0.0, 0.0);

	// Spine wire: line → semicircle → line.
	let up_leg = Edge::line(a, b)?;
	let bend = Edge::arc_3pts(b, arc_mid, c)?;
	let down_leg = Edge::line(c, d)?;

	// Circular profile in XY (normal +Z) translated to the spine start `a`.
	// Spine tangent at `a` is +Z, so the XY-plane circle is already aligned.
	let profile = Edge::circle(pipe_radius, DVec3::Z)?.translate(a);

	// Up(+Y) fixes the binormal to the path-plane normal, avoiding Frenet
	// degeneracy on the straight segments.
	let pipe = Solid::sweep(&[profile], &[up_leg, bend, down_leg], ProfileOrient::Up(DVec3::Y))?;
	Ok(pipe.translate(DVec3::X * 6.0).color("blue"))
}

// ==================== Component 3: Auxiliary-spine twisted ribbon ====================

// Sweeping a straight spine with `Auxiliary(&[helix])` rotates the tracked
// axis of the profile at each point to face the corresponding helix point.
// A pitch=h helix makes exactly one 360° turn over [0, h], so a flat
// rectangular profile becomes a ribbon twisted once. With `Fixed` or
// `Torsion` the profile wouldn't rotate along a straight spine — visible
// twist is therefore proof that Auxiliary is in effect.
fn build_twisted_ribbon() -> Result<Solid, Error> {
	let h = 8.0;
	let aux_r = 3.0;

	let spine = Edge::line(DVec3::ZERO, DVec3::Z * h)?;
	let aux = Edge::helix(aux_r, h, h, DVec3::Z, DVec3::X)?;

	// Flat rectangle (10:1 aspect) — circles or squares wouldn't reveal any twist.
	let profile = Edge::polygon(&[DVec3::new(-2.0, -0.2, 0.0), DVec3::new(2.0, -0.2, 0.0), DVec3::new(2.0, 0.2, 0.0), DVec3::new(-2.0, 0.2, 0.0)])?;

	let ribbon = Solid::sweep(&profile, &[spine], ProfileOrient::Auxiliary(&[aux]))?;
	Ok(ribbon.translate(DVec3::X * 12.0).color("green"))
}

// ==================== main: side-by-side layout ====================
//
// Each builder places its component at its final world position (screw at
// origin, U-pipe at x=6, ribbon at x=12) and applies its color, so main
// just concatenates them.

fn main() -> Result<(), Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();
	let all = [build_m2_screw()?, build_u_pipe()?, build_twisted_ribbon()?];

	Solid::write_step(&all, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	// Helical threads have dense hidden lines that clutter the output; disable them.
	let scene = Solid::mesh(&all, 0.5)?.scene(DVec3::new(1.0, 1.0, -1.0), DVec3::Z, false, false);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png ({} solids)", all.len());
	Ok(())
}

```
- [07_sweep.png](https://lzpel.github.io/cadrum/07_sweep.png)
- [07_sweep.step](https://lzpel.github.io/cadrum/07_sweep.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/07_sweep.svg" alt="07_sweep" width="360"/>
</p>

#### Shell

Demo of `Solid::shell`:

```sh
cargo run --example 08_shell
```

```rust,no_run
//! Demo of `Solid::shell`:
//! - Cube: remove top face, offset inward → open-top container
//! - Sealed cube: empty open_faces → solid with an internal void (outer skin
//!   + reversed inner shell)
//! - Torus: bisect with a half-space to introduce planar cut faces, then
//!   shell using those cut faces as the openings → thin-walled half-ring
//!   with both cross-sections exposed

use cadrum::{DVec3, Error, Solid};

fn hollow_cube() -> Result<Solid, Error> {
	let cube = Solid::cube(8.0, 8.0, 8.0);
	// TopExp_Explorer order on a box is stable; +Z face ends up last.
	let top = cube.iter_face().last().expect("cube has faces");
	cube.shell(-1.0, [top])
}

fn sealed_cube() -> Result<Solid, Error> {
	let cube = Solid::cube(8.0, 8.0, 8.0);
	cube.shell(-1.0, std::iter::empty::<&cadrum::Face>())
}

fn halved_shelled_torus(thickness: f64) -> Result<Solid, Error> {
	let torus = Solid::torus(6.0, 2.0, DVec3::Y);
	// Bisect with Y=0 half-space (normal +Y): keep the +Y half of the ring — always 1 solid.
	let cutter = Solid::half_space(DVec3::ZERO, -DVec3::Z);
	// `iter_history()` yields [post_id, src_id] pairs for every result face.
	// Filter to those whose src_id is one of the cutter's faces, then collect
	// their post_ids — these are the planar cut faces in the result that we
	// want to use as shell openings.
	let cutter_face_ids: std::collections::HashSet<u64> =
		cutter.iter_face().map(|f| f.id()).collect();
	let half = (&torus * &cutter)?;
	let from_cutter: std::collections::HashSet<u64> = half
		.iter_history()
		.filter_map(|[post, src]| cutter_face_ids.contains(&src).then_some(post))
		.collect();
	half.shell(thickness, half.iter_face().filter(|f| from_cutter.contains(&f.id())))
}

fn main() -> Result<(), Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let result = [
		hollow_cube()?.color("#d0a878"),
		sealed_cube()?.color("#6fbf73").translate(DVec3::Y * 10.0),
		halved_shelled_torus(1.0)?.color("#ff5e00").translate(DVec3::X * 18.0),
		halved_shelled_torus(-1.0)?.color("#0052ff").translate(DVec3::X * 18.0 + DVec3::Y * 10.0),
	];

	Solid::write_step(&result, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	// Isometric view from (1, 1, 2) with shading so the cavity depth reads
	// naturally.
	let scene = Solid::mesh(&result, 0.2)?.scene(DVec3::new(1.0, 1.0, 2.0), DVec3::Z, true, true);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
	Ok(())
}

```
- [08_shell.png](https://lzpel.github.io/cadrum/08_shell.png)
- [08_shell.step](https://lzpel.github.io/cadrum/08_shell.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/08_shell.svg" alt="08_shell" width="360"/>
</p>

#### Bspline

```sh
cargo run --example 09_bspline
```

```rust,no_run
use cadrum::{DQuat, DVec3, Solid};
use std::f64::consts::TAU;

// 2 field-period stellarator-like torus.
// `Solid::bspline` is fed a 2D control-point grid to build a periodic B-spline solid.
// Every variation below is invariant under phi → phi+π (or shifts by a multiple
// of 2π), so the resulting shape has 180° rotational symmetry around the Z axis:
//   a(phi)       = 1.8 + 0.6 * sin(2φ)      radial semi-axis
//   b(phi)       = 1.0 + 0.4 * cos(2φ)      Z semi-axis
//   psi(phi)     = 2 * phi                  cross-section twist (2 turns per loop)
//   z_shift(phi) = 1.0 * sin(2φ)            vertical undulation
const M: usize = 48; // toroidal (U) — must be even for 180° symmetry
const N: usize = 24; // poloidal (V) — arbitrary
const RING_R: f64 = 6.0;

fn point(i: usize, j: usize) -> DVec3 {
	let phi = TAU * (i as f64) / (M as f64);
	let theta = TAU * (j as f64) / (N as f64);
	let two_phi = 2.0 * phi;
	let a = 1.8 + 0.6 * two_phi.sin();
	let b = 1.0 + 0.4 * two_phi.cos();
	let psi = two_phi; // twist: 2 full turns per toroidal loop
	let z_shift = 1.0 * two_phi.sin();
	// 1. Local cross-section (pre-twist ellipse in the (X, Z) plane)
	let local_raw = DVec3::X * (a * theta.cos()) + DVec3::Z * (b * theta.sin());
	// 2. Rotate by psi around the local Y axis (major-circle tangent) — the twist
	let local_twisted = DQuat::from_axis_angle(DVec3::Y, psi) * local_raw;
	// 3. Undulate vertically in the local frame
	let local_shifted = local_twisted + DVec3::Z * z_shift;
	// 4. Push outward along the major radius by RING_R
	let translated = local_shifted + DVec3::X * RING_R;
	// 5. Rotate the whole point around the global Z axis by phi
	DQuat::from_axis_angle(DVec3::Z, phi) * translated
}

fn main() -> Result<(), cadrum::Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let plasma = Solid::bspline(M, N, true, point).expect("2-period bspline torus should succeed");
	let objects = [plasma.color("cyan")];

	Solid::write_step(&objects, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	let scene = Solid::mesh(&objects, 0.05)?.scene(DVec3::new(0.05, 0.05, 1.0), DVec3::Y, false, true);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
	Ok(())
}

```
- [09_bspline.png](https://lzpel.github.io/cadrum/09_bspline.png)
- [09_bspline.step](https://lzpel.github.io/cadrum/09_bspline.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/09_bspline.svg" alt="09_bspline" width="360"/>
</p>

#### Fillet

Demo of `Solid::fillet_edges`:

```sh
cargo run --example 10_fillet
```

```rust,no_run
//! Demo of `Solid::fillet_edges`:
//! - All 12 cube edges filleted uniformly (rounded cube)
//! - Only top 4 edges filleted (soft top, sharp base)
//! - Cylinder top circular edge filleted (coin shape)

use cadrum::{DVec3, Error, Solid};

fn rounded_cube(size: f64) -> Result<Solid, Error> {
	let cube = Solid::cube(size, size, size).translate(-DVec3::ONE * (size / 2.0));
	let radius = size * 0.2;
	cube.fillet_edges(radius, cube.iter_edge())
}

fn soft_top_cube(size: f64) -> Result<Solid, Error> {
	let cube = Solid::cube(size, size, size).translate(-DVec3::ONE * (size / 2.0));
	let radius = size * 0.2;
	// Top cap boundary: a closed circular edge whose start == end lives at z = h.
	let top_edges = cube
		.iter_edge()
		.filter(|e| [e.start_point(), e.end_point()].iter().all(|p| (p.z - size / 2.0).abs() < 1e-6));
	cube.fillet_edges(radius, top_edges)
}

fn coin(radius: f64, height: f64) -> Result<Solid, Error> {
	let cyl = Solid::cylinder(radius, DVec3::Z, height);
	let radius = height * 0.3;
	// Top cap boundary: a closed circular edge whose start == end lives at z = h.
	let top_circle = cyl
		.iter_edge()
		.filter(|e| [e.start_point(), e.end_point()].iter().all(|p| (p.z - height).abs() < 1e-6));
	cyl.fillet_edges(radius, top_circle)
}

fn main() -> Result<(), Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let result = [
		rounded_cube(8.0)?.color("#d0a878"),
		soft_top_cube(8.0)?.color("#6fbf73").translate(DVec3::X * 12.0),
		coin(4.0, 2.0)?.color("#0052ff").translate(DVec3::X * 24.0),
	];

	Solid::write_step(&result, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	let scene = Solid::mesh(&result, 0.2)?.scene(DVec3::new(1.0, 1.0, 2.0), DVec3::Z, true, true);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
	Ok(())
}

```
- [10_fillet.png](https://lzpel.github.io/cadrum/10_fillet.png)
- [10_fillet.step](https://lzpel.github.io/cadrum/10_fillet.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/10_fillet.svg" alt="10_fillet" width="360"/>
</p>

#### Chamfer

Demo of `Solid::chamfer_edges` — mirror of `10_fillet.rs` using bevels:

```sh
cargo run --example 11_chamfer
```

```rust,no_run
//! Demo of `Solid::chamfer_edges` — mirror of `10_fillet.rs` using bevels:
//! - All 12 cube edges chamfered uniformly (beveled cube)
//! - Only top 4 edges chamfered (soft top, sharp base)
//! - Cylinder top circular edge chamfered (coin with beveled rim)

use cadrum::{DVec3, Error, Solid};

fn beveled_cube(size: f64) -> Result<Solid, Error> {
	let cube = Solid::cube(size, size, size).translate(-DVec3::ONE * (size / 2.0));
	let distance = size * 0.2;
	cube.chamfer_edges(distance, cube.iter_edge())
}

fn beveled_top_cube(size: f64) -> Result<Solid, Error> {
	let cube = Solid::cube(size, size, size).translate(-DVec3::ONE * (size / 2.0));
	let distance = size * 0.2;
	// Top cap boundary: a closed circular edge whose start == end lives at z = h.
	let top_edges = cube
		.iter_edge()
		.filter(|e| [e.start_point(), e.end_point()].iter().all(|p| (p.z - size / 2.0).abs() < 1e-6));
	cube.chamfer_edges(distance, top_edges)
}

fn beveled_coin(radius: f64, height: f64) -> Result<Solid, Error> {
	let cyl = Solid::cylinder(radius, DVec3::Z, height);
	let distance = height * 0.3;
	// Top cap boundary: a closed circular edge whose start == end lives at z = h.
	let top_circle = cyl
		.iter_edge()
		.filter(|e| [e.start_point(), e.end_point()].iter().all(|p| (p.z - height).abs() < 1e-6));
	cyl.chamfer_edges(distance, top_circle)
}

fn main() -> Result<(), Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let result = [
		beveled_cube(8.0)?.color("#d0a878"),
		beveled_top_cube(8.0)?.color("#6fbf73").translate(DVec3::X * 12.0),
		beveled_coin(4.0, 2.0)?.color("#0052ff").translate(DVec3::X * 24.0),
	];

	Solid::write_step(&result, &mut std::fs::File::create(format!("{example_name}.step")).unwrap())?;

	let scene = Solid::mesh(&result, 0.2)?.scene(DVec3::new(1.0, 1.0, 2.0), DVec3::Z, true, true);
	scene.write_svg(&mut std::fs::File::create(format!("{example_name}.svg")).unwrap())?;
	scene.write_png([640, 640], &mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.step / {example_name}.svg / {example_name}.png");
	Ok(())
}

```
- [11_chamfer.png](https://lzpel.github.io/cadrum/11_chamfer.png)
- [11_chamfer.step](https://lzpel.github.io/cadrum/11_chamfer.step)

<p align="center">
  <img src="https://lzpel.github.io/cadrum/11_chamfer.svg" alt="11_chamfer" width="360"/>
</p>

#### Multiview

Fixed 4-view multiview PNG for LLM-driven design loops.

```sh
cargo run --example 12_multiview
```

```rust,no_run
//! Fixed 4-view multiview PNG for LLM-driven design loops.
//!
//! A single call to `Solid::write_multiview_png` produces a 1024×1024 PNG that lays out
//! 4 views — ISO plus the axis cyclic order (+X / +Y / +Z) — at the same scale. With no
//! parameters to tune, Solid maps 1:1 to an image, which suits state-snapshot rendering
//! for LLMs and automated design loops.

use cadrum::{DVec3, Solid};

fn main() -> Result<(), cadrum::Error> {
	let example_name = std::path::Path::new(file!()).file_stem().unwrap().to_str().unwrap();

	let block = Solid::cube(40.0, 30.0, 20.0)
		.translate(-DVec3::new(20.0, 15.0, 10.0));
	let hole = Solid::cylinder(5.0, DVec3::Z, 30.0)
		.translate(-DVec3::Z * 15.0);
	// Axis-orientation check: carve only the +X+Y+Z corner with a sphere.
	// Which corner the notch appears in on each panel uniquely confirms the gnomon's direction.
	let corner_cut = Solid::sphere(10.0)
		.translate(DVec3::new(20.0, 15.0, 10.0));
	let part = (&block - &hole)?;
	let part = (&part - &corner_cut)?;

	part.write_multiview_png(&mut std::fs::File::create(format!("{example_name}.png")).unwrap())?;

	println!("wrote {example_name}.png");
	Ok(())
}

```
- [12_multiview.png](https://lzpel.github.io/cadrum/12_multiview.png)


## The Type Map

Three concrete shape types and two trait umbrellas form the whole public
surface:

```text
    Edge  ── single 3D curve         ┐
    Face  ── trimmed 3D surface      │ concrete BRep handles
    Solid ── connected closed body   ┘

    Wire     ── trait carrying methods on Edge / Vec<Edge> / [Edge; N]
    Compound ── trait carrying methods on Solid / Vec<Solid> / [Solid; N]
```

On a single `Solid` or single `Edge`, every method is reachable inherently —
no trait import needed:

```rust,no_run
# use cadrum::{DVec3, Solid};
let s = Solid::cube(1.0, 1.0, 1.0).rotate_z(0.5).translate(DVec3::X);
let v = s.volume();
```

On a `Vec<Solid>` or `[Solid; N]`, the same operations live behind the
`Compound` trait. A single `use cadrum::Compound;` brings them into scope
on the collection — including the spatial transforms, which on collections
distribute element-wise:

```rust,no_run
use cadrum::{Compound, DVec3, Solid};

let parts: Vec<Solid> = vec![
    Solid::cube(1.0, 1.0, 1.0),
    Solid::sphere(1.0),
];
let shifted = parts.translate(DVec3::X * 5.0);
let total   = shifted.volume();        // Σ per-element volumes
let bbox    = shifted.bounding_box();  // union AABB
```

`Vec<Edge>` plays the equivalent role for wires (open or closed polylines
made of edges) under `Wire`. There is no separate `Wire` type — an ordered
`Vec<Edge>` *is* a wire, and sweep / loft / extrude all take any
`IntoIterator<Item = &Edge>`.

### Spatial transforms across the whole hierarchy

The transform family — `translate`, `rotate`, `rotate_x` / `_y` / `_z`,
`scale`, `mirror`, `align_x` / `_y` / `_z` — is implemented identically on
every shape and every collection. The same method name and signature works
on:

- a single `Solid` — `cube.rotate_z(angle)`
- a single `Edge` — `circle.translate(offset)`
- `Vec<Solid>` / `[Solid; N]` via `Compound` — element-wise
- `Vec<Edge>` / `[Edge; N]` via `Wire` — element-wise

```rust,no_run
use cadrum::{Compound, DVec3, Edge, Solid, Wire};
use std::f64::consts::FRAC_PI_4;

let s: Solid          = Solid::sphere(1.0).translate(DVec3::X);
let e: Edge           = Edge::circle(1.0, DVec3::Z)?.rotate_x(FRAC_PI_4);
let v_s: Vec<Solid>   = vec![Solid::cube(1.0, 1.0, 1.0)].translate(DVec3::Y);
let v_e: Vec<Edge>    = Edge::polygon(&[
    DVec3::ZERO, DVec3::X, DVec3::X + DVec3::Y, DVec3::Y,
])?.rotate_z(FRAC_PI_4);
# Ok::<(), cadrum::Error>(())
```

On `Solid` / `Edge` themselves the methods are inherent (no import
required); on collections `use cadrum::Compound;` / `use cadrum::Wire;`
brings them into scope.

## Working with Wires

Wire constructors return either a single `Edge` or `Vec<Edge>` depending on
what is natural for the curve:

```rust,no_run
use cadrum::{BSplineEnd, DVec3, Edge};

// Single-edge primitives → Edge
let line   = Edge::line(DVec3::ZERO, DVec3::X)?;
let arc    = Edge::arc_3pts(DVec3::ZERO, DVec3::X, DVec3::Y)?;
let circle = Edge::circle(1.0, DVec3::Z)?;
let helix  = Edge::helix(1.0, 0.4, 6.0, DVec3::Z, DVec3::X)?;

// Multi-edge primitive → Vec<Edge>
let square = Edge::polygon(&[
    DVec3::new(0.0, 0.0, 0.0),
    DVec3::new(1.0, 0.0, 0.0),
    DVec3::new(1.0, 1.0, 0.0),
    DVec3::new(0.0, 1.0, 0.0),
])?;

// Free-form curve → Edge (single B-spline)
let curve = Edge::bspline(
    &[DVec3::ZERO, DVec3::X, DVec3::X + DVec3::Y, DVec3::Y],
    BSplineEnd::NotAKnot,
)?;
# Ok::<(), cadrum::Error>(())
```

Either shape feeds `Solid::extrude`, `Solid::sweep`, or `Solid::loft`
uniformly because they take `IntoIterator<Item = &Edge>`:

```rust,no_run
# use cadrum::{DVec3, Edge, Solid};
# let circle = Edge::circle(1.0, DVec3::Z)?;
# let square: Vec<Edge> = vec![];
let s1 = Solid::extrude(&[circle], DVec3::Z * 5.0)?;
let s2 = Solid::extrude(&square,   DVec3::Z * 5.0)?;
# Ok::<(), cadrum::Error>(())
```

Pass a single edge as `&[edge]` rather than relying on a sugar that lets
`&edge` adapt — the slice form keeps the "this function consumes a
collection" intent visible at the call site.

## Booleans and Topology History

Boolean operations return `Vec<Solid>` because a subtraction or
intersection can split into several disjoint pieces. Each result solid
carries a `Solid::iter_history` log of `[post_id, src_id]` pairs — every
face in the result remembers which face of which input it came from. That
makes face selectors stable across boolean stages:

```rust,no_run
use cadrum::{Compound, DVec3, Solid};

let block = Solid::cube(20.0, 20.0, 20.0);
let hole  = Solid::cylinder(8.0, DVec3::Z, 30.0)
    .translate(DVec3::new(10.0, 10.0, -5.0));

let drilled = Solid::boolean_subtract([&block], [&hole])?;
let from_block: Vec<u64> = drilled[0]
    .iter_history()
    .filter(|[_, src]| *src == block.id())   // faces inherited from `block`
    .map(|[post, _]| post)
    .collect();
# Ok::<(), cadrum::Error>(())
```

See `examples/08_shell.rs` for a worked end-to-end use of this mechanism
(shelling a torus through cut faces produced by a half-space subtraction).

## Mesh and Visual Output

`Solid::mesh` flattens any number of solids into a single triangle `Mesh`
using OCCT's BRep mesher (`BRepMesh_IncrementalMesh`). From a `Mesh`,
`Mesh::write_stl` emits a binary STL; `Mesh::scene` builds a backend-
agnostic `Scene2D` (projection + shading + silhouette + occlusion) which
each 2D backend (currently SVG) consumes — handy for documentation and
quick visual diffs:

```rust,no_run
use cadrum::{DVec3, Solid};

let parts = [Solid::cube(10.0, 20.0, 30.0)];
let mesh  = Solid::mesh(&parts, 0.5)?;

mesh.write_stl(&mut std::fs::File::create("out.stl").unwrap())?;
mesh.scene(
    DVec3::ONE,   // view direction
    DVec3::Z,     // up direction
    true,         // classify hidden lines
    false,        // Lambertian shading off
).write_svg(&mut std::fs::File::create("out.svg").unwrap())?;
# Ok::<(), cadrum::Error>(())
```

## Errors

Every fallible operation returns `Result<T, Error>` with `Error`
enumerating the failure modes (`Error::SweepFailed`,
`Error::FilletFailed`, `Error::InvalidEdge`, etc.). Variants that need
detail carry a `String` payload identifying which constructor or parameter
combination tripped OCCT, so panics are reserved for true logic bugs.

## Features

- **`color`** *(default)*: Enables `Solid::color` and per-face colormap
  propagation through STEP / BRep / STL / SVG I/O via OCCT's XDE document
  model. Disable for a smaller binary if shape color is irrelevant.
- **`source-build`**: When the prebuilt-binary cache is empty, fall back
  to building OCCT from upstream sources via CMake instead of failing.
  Required on targets without a published prebuilt (anything outside the
  four-way Linux / Windows × x86_64 / aarch64 table). Pulls `cmake` in as
  a build-dep.

## Showcase

[Try it now →](https://katachiform.com/out/21)

A browser-based configurator that lets you tweak dimensions of a STEP model and get an instant 3D preview and quote. cadrum powers the parametric reshaping and meshing on the backend.

## License

This project is licensed under the MIT License.

Compiled binaries include [OpenCASCADE Technology][occt] (OCCT),
which is licensed under the [LGPL 2.1][occt-license].
Users who distribute applications built with cadrum must comply with the LGPL 2.1 terms.
Since cadrum builds OCCT from source, end users can rebuild and relink OCCT to satisfy this requirement.

<!-- Badges -->
[license_img]: https://img.shields.io/github/license/lzpel/cadrum
[license_link]: https://github.com/lzpel/cadrum/blob/main/LICENSE
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[docsrs_link]: https://docs.rs/cadrum

<!-- External References -->
[occt]: https://dev.opencascade.org/
[occt-license]: https://dev.opencascade.org/resources/licensing
