How can I manually create meshes in bevy with vertices?

Question

What do I have to do to to create a mesh for bevy with the following vertices:

let mut vertices : Vec<[f32; 3]> = Vec::new();

    vertices.push([0.0, 0.0, 0.0]);
    vertices.push([1.0, 2.0, 1.0]);
    vertices.push([2.0, 0.0, 0.0]);

I then want to spawn a MeshBundle like so

commands
    .spawn(MeshBundle {
        mesh: mesh,
        transform: Transform::from_translation(Vec3::new(0.0, 0.0, 0.0)),
        ..Default::default()
    });

Answer 1

This answer has been updated for the latest bevy = "0.11" and uses the default shaders.

The code below demonstrates how to:

1. Define vertex positions for a bevy::render::pipeline::PrimitiveTopology::TriangleList
2. Assign vertex normals and uv coordinates to the vertices
3. Create a triangle using the 3 vertices we defined

It is based on the built in shapes in bevy, which can be found here.

use bevy::prelude::*;
use bevy::render::mesh::{self, PrimitiveTopology};

fn main() {
    App::new()
        .insert_resource(Msaa::Sample4)
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);

    // Positions of the vertices
    // See https://bevy-cheatbook.github.io/features/coords.html
    mesh.insert_attribute(
        Mesh::ATTRIBUTE_POSITION,
        vec![[0., 0., 0.], [1., 2., 1.], [2., 0., 0.]],
    );

    // In this example, normals and UVs don't matter,
    // so we just use the same value for all of them
    mesh.insert_attribute(Mesh::ATTRIBUTE_NORMAL, vec![[0., 1., 0.]; 3]);
    mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, vec![[0., 0.]; 3]);

    // A triangle using vertices 0, 2, and 1.
    // Note: order matters. [0, 1, 2] will be flipped upside down, and you won't see it from behind!
    mesh.set_indices(Some(mesh::Indices::U32(vec![0, 2, 1])));

    commands.spawn(PbrBundle {
        mesh: meshes.add(mesh),
        material: materials.add(Color::rgb(0.3, 0.5, 0.3).into()),
        ..default()
    });

    commands.spawn(PointLightBundle {
        point_light: PointLight {
            intensity: 1500.0,
            shadows_enabled: true,
            ..default()
        },
        transform: Transform::from_xyz(4.0, 8.0, 4.0),
        ..default()
    });

    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });
}

You will have to define your own positions, uvs and normals according to your use case. Some shaders won't need all of these mesh attributes.