Hexahedron (Cube)

Add the hexahedron module

src/lib.rs additions:

#![allow(unused)]
fn main() {
use truck_meshalgo::prelude::*;

// ...keep earlier functions: write_polygon_mesh, triangle, square, tetrahedron...
pub mod hexahedron; //add this
pub use hexahedron::hexahedron; //add this
}

Construct Main Function

src/hexahedron.rs:

#![allow(unused)]
fn main() {
use std::iter::FromIterator;
use truck_meshalgo::prelude::*;

/// Unit cube (hexahedron) using quads.
pub fn hexahedron() -> PolygonMesh {

    //PLACE STEP 1-4 HERE

}
}

Step 1: Define vertex positions

#![allow(unused)]
fn main() {
    let positions = vec![
        Point3::new(0.0, 0.0, 0.0), //[0]
        Point3::new(1.0, 0.0, 0.0), //[1]
        Point3::new(1.0, 1.0, 0.0), //[2]
        Point3::new(0.0, 1.0, 0.0), //[3]
        Point3::new(0.0, 0.0, 1.0), //[4]
        Point3::new(1.0, 0.0, 1.0), //[5]
        Point3::new(1.0, 1.0, 1.0), //[6]
        Point3::new(0.0, 1.0, 1.0), //[7]
    ];
}

Step 2: Build attribute set

#![allow(unused)]
fn main() {
    let attrs = StandardAttributes {
        positions,
        ..Default::default()
    };

}

Step 3: Define mesh faces

#![allow(unused)]
fn main() {
    let faces = Faces::from_iter([
        [3, 2, 1, 0], // bottom
        [0, 1, 5, 4], // front
        [1, 2, 6, 5], // right
        [2, 3, 7, 6], // back
        [3, 0, 4, 7], // left
        [4, 5, 6, 7], // top
    ]);
}

Cube illustration

Step 4: Construct the mesh

#![allow(unused)]
fn main() {
    PolygonMesh::new(attrs, faces)
}

Export the cube

Add examples/hexahedron.rs:

fn main() {
    let mesh = truck_meshes::hexahedron();
    truck_meshes::write_polygon_mesh(&mesh, "output/hexahedron.obj");
}

Run it:

cargo run --example hexahedron

View it

Open output/hexahedron.obj in Preview/3D Viewer/ParaView/Blender. You should see a single hexahedron.

gif below from Preview (mac).

Hexahedron

File tree after this step

truck_meshes/
├─ Cargo.toml
├─ src/
│  ├─ lib.rs
│  ├─ triangle.rs
│  ├─ square.rs
│  ├─ tetrahedron.rs
│  └─ hexahedron.rs
├─ examples/
│  ├─ triangle.rs
│  ├─ square.rs
│  ├─ tetrahedron.rs
│  └─ hexahedron.rs
└─ output/          # exported OBJ files (e.g., output/hexahedron.obj)

Full code:

src/lib.rs:

#![allow(unused)]
fn main() {
use truck_meshalgo::prelude::*;

/// Write any mesh to an OBJ file.
pub fn write_polygon_mesh(mesh: &PolygonMesh, path: &str) {
    let mut obj = std::fs::File::create(path).unwrap();
    obj::write(mesh, &mut obj).unwrap();
}

pub mod triangle;
pub use triangle::triangle;

pub mod square;
pub use square::square;

pub mod tetrahedron;
pub use tetrahedron::tetrahedron;

pub mod hexahedron;
pub use hexahedron::hexahedron;
}

src/hexahedron.rs:

#![allow(unused)]
fn main() {
use std::iter::FromIterator;
use truck_meshalgo::prelude::*;

pub fn hexahedron() -> PolygonMesh {
    let positions = vec![
        Point3::new(0.0, 0.0, 0.0),
        Point3::new(1.0, 0.0, 0.0),
        Point3::new(1.0, 1.0, 0.0),
        Point3::new(0.0, 1.0, 0.0),
        Point3::new(0.0, 0.0, 1.0),
        Point3::new(1.0, 0.0, 1.0),
        Point3::new(1.0, 1.0, 1.0),
        Point3::new(0.0, 1.0, 1.0),
    ];

    let attrs = StandardAttributes {
        positions,
        ..Default::default()
    };

    let faces = Faces::from_iter([
        [3, 2, 1, 0],
        [0, 1, 5, 4],
        [1, 2, 6, 5],
        [2, 3, 7, 6],
        [3, 0, 4, 7],
        [4, 5, 6, 7],
    ]);

    PolygonMesh::new(attrs, faces)
}
}

examples/hexahedron.rs:

fn main() {
    let mesh = truck_meshes::hexahedron();
    truck_meshes::write_polygon_mesh(&mesh, "output/hexahedron.obj");
}

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