1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78

use bevy_math::primitives::Cuboid;
use wgpu::PrimitiveTopology;

use crate::{
    mesh::{Indices, Mesh, Meshable},
    render_asset::RenderAssetUsages,
};

impl Meshable for Cuboid {
    type Output = Mesh;

    fn mesh(&self) -> Self::Output {
        let min = -self.half_size;
        let max = self.half_size;

        // Suppose Y-up right hand, and camera look from +Z to -Z
        let vertices = &[
            // Front
            ([min.x, min.y, max.z], [0.0, 0.0, 1.0], [0.0, 0.0]),
            ([max.x, min.y, max.z], [0.0, 0.0, 1.0], [1.0, 0.0]),
            ([max.x, max.y, max.z], [0.0, 0.0, 1.0], [1.0, 1.0]),
            ([min.x, max.y, max.z], [0.0, 0.0, 1.0], [0.0, 1.0]),
            // Back
            ([min.x, max.y, min.z], [0.0, 0.0, -1.0], [1.0, 0.0]),
            ([max.x, max.y, min.z], [0.0, 0.0, -1.0], [0.0, 0.0]),
            ([max.x, min.y, min.z], [0.0, 0.0, -1.0], [0.0, 1.0]),
            ([min.x, min.y, min.z], [0.0, 0.0, -1.0], [1.0, 1.0]),
            // Right
            ([max.x, min.y, min.z], [1.0, 0.0, 0.0], [0.0, 0.0]),
            ([max.x, max.y, min.z], [1.0, 0.0, 0.0], [1.0, 0.0]),
            ([max.x, max.y, max.z], [1.0, 0.0, 0.0], [1.0, 1.0]),
            ([max.x, min.y, max.z], [1.0, 0.0, 0.0], [0.0, 1.0]),
            // Left
            ([min.x, min.y, max.z], [-1.0, 0.0, 0.0], [1.0, 0.0]),
            ([min.x, max.y, max.z], [-1.0, 0.0, 0.0], [0.0, 0.0]),
            ([min.x, max.y, min.z], [-1.0, 0.0, 0.0], [0.0, 1.0]),
            ([min.x, min.y, min.z], [-1.0, 0.0, 0.0], [1.0, 1.0]),
            // Top
            ([max.x, max.y, min.z], [0.0, 1.0, 0.0], [1.0, 0.0]),
            ([min.x, max.y, min.z], [0.0, 1.0, 0.0], [0.0, 0.0]),
            ([min.x, max.y, max.z], [0.0, 1.0, 0.0], [0.0, 1.0]),
            ([max.x, max.y, max.z], [0.0, 1.0, 0.0], [1.0, 1.0]),
            // Bottom
            ([max.x, min.y, max.z], [0.0, -1.0, 0.0], [0.0, 0.0]),
            ([min.x, min.y, max.z], [0.0, -1.0, 0.0], [1.0, 0.0]),
            ([min.x, min.y, min.z], [0.0, -1.0, 0.0], [1.0, 1.0]),
            ([max.x, min.y, min.z], [0.0, -1.0, 0.0], [0.0, 1.0]),
        ];

        let positions: Vec<_> = vertices.iter().map(|(p, _, _)| *p).collect();
        let normals: Vec<_> = vertices.iter().map(|(_, n, _)| *n).collect();
        let uvs: Vec<_> = vertices.iter().map(|(_, _, uv)| *uv).collect();

        let indices = Indices::U32(vec![
            0, 1, 2, 2, 3, 0, // front
            4, 5, 6, 6, 7, 4, // back
            8, 9, 10, 10, 11, 8, // right
            12, 13, 14, 14, 15, 12, // left
            16, 17, 18, 18, 19, 16, // top
            20, 21, 22, 22, 23, 20, // bottom
        ]);

        Mesh::new(
            PrimitiveTopology::TriangleList,
            RenderAssetUsages::default(),
        )
        .with_inserted_attribute(Mesh::ATTRIBUTE_POSITION, positions)
        .with_inserted_attribute(Mesh::ATTRIBUTE_NORMAL, normals)
        .with_inserted_attribute(Mesh::ATTRIBUTE_UV_0, uvs)
        .with_inserted_indices(indices)
    }
}

impl From<Cuboid> for Mesh {
    fn from(cuboid: Cuboid) -> Self {
        cuboid.mesh()
    }
}