Out-of-range panic when generating a basic procedural mesh

[luca-aurelia]

Hey folks! I'm thinking about using Bevy for doing generative art, which means procedurally generating meshes. As a test, I'm trying to procedurally generate a circle mesh.

I've written some code, but I'm getting an out-of-range panic (panicked at 'range end index 320 out of range for slice of length 288') and I'm not sure what's causing it.

Here's my mesh generation code:

fn get_circle_mesh(center: [f32; 3], radius: f32, num_sides: usize) -> Mesh {
    let [center_x, center_y, center_z] = center;

    let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);

    let mut positions = Vec::with_capacity(num_sides);
    let mut indexes: Vec<u16> = Vec::with_capacity(num_sides * 3);
    let mut normals = Vec::with_capacity(num_sides);
    let mut uvs = Vec::with_capacity(num_sides);

    positions.push(center);
    normals.push([0.0, 0.0, 1.0]);
    uvs.push([0.0, 0.0, 1.0]);

    for i in 1..=num_sides {
        let progress = (i - 1) as f32 / num_sides as f32;

        // Generate circle vertices.
        let rotation = progress * TAU;
        let x = center_x + radius * rotation.cos();
        let y = center_y + radius * rotation.sin();
        positions.push([x, y, center_z]);

        // Get indexes.
        let mut next_index = i + 1;
        if next_index > num_sides {
            next_index = 1;
        }

        indexes.push(0);
        indexes.push(i as u16);
        indexes.push(next_index as u16);

        normals.push([0.0, 0.0, 1.0]);
        uvs.push([0.0, 0.0, 1.0]);
    }

    // Set mesh vertex positions
    mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, positions);
    // Set mesh vertex normals
    mesh.insert_attribute(Mesh::ATTRIBUTE_NORMAL, normals);
    // Set mesh vertex UVs. Although the mesh doesn't have any texture applied,
    //  UVs are still required by the render pipeline. So these UVs are zeroed out.
    mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, uvs);
    // Tell bevy to construct triangles from a list of vertex indices,
    //  where each 3 vertex indices form an triangle.
    mesh.set_indices(Some(Indices::U16(indexes)));

    mesh
}

And my setup code:

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .insert_resource(AmbientLight {
            brightness: 1.0,
            ..Default::default()
        })
        .add_startup_system(setup)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    // Create a camera
    commands.spawn_bundle(PerspectiveCameraBundle {
        transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });

    let circle_mesh = get_circle_mesh([0.0, 0.0, 0.0], 1.0, 8);
    let circle_mesh_handle = meshes.add(circle_mesh);

    commands.spawn_bundle(PbrBundle {
        mesh: circle_mesh_handle,
        material: materials.add(Color::rgb(0.0, 0.0, 1.0).into()),
        transform: Transform::from_xyz(0.0, 0.0, 0.0),
        ..Default::default()
    });
}

[afonsolage]

Mesh::ATTRIBUTE_UV_0 has the type VertexFormat::Float32x2 so you should use a [f32; 2].

Here is the problem:

uvs.push([0.0, 0.0, 1.0]);

Just set to:

uvs.push([0.0, 0.0]);

And it should work fine.

Edit: This question was already answered on Discord by IceSentry, which already sent an PR to solve this issue.