How can I manually create meshes in bevy with vertices? - rust

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 = "0.9.1" and uses the default shaders.
The code below demonstrates how to:
Define vertex positions for a bevy::render::pipeline::PrimitiveTopology::TriangleList
Assign vertex normals and uv coordinates to the vertices
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 { samples: 4 })
.add_plugins(DefaultPlugins)
.add_startup_system(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.

Answer 2

#frankenapps answer updated for bevy = 0.7
use bevy::prelude::*;
use bevy::render::mesh::{self, PrimitiveTopology};
fn main() {
App::new()
.insert_resource(Msaa { samples: 4 })
.add_plugins(DefaultPlugins)
.add_startup_system(setup)
.run();
}
/// set up a simple 3D scene
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
let vertices = [
([0.0, 0.0, 0.0], [0.0, 1.0, 0.0], [1.0, 1.0]),
([1.0, 2.0, 1.0], [0.0, 1.0, 0.0], [1.0, 1.0]),
([2.0, 0.0, 0.0], [0.0, 1.0, 0.0], [1.0, 1.0]),
];
let indices = mesh::Indices::U32(vec![0, 2, 1, 0, 3, 2]);
let mut positions = Vec::new();
let mut normals = Vec::new();
let mut uvs = Vec::new();
for (position, normal, uv) in vertices.iter() {
positions.push(*position);
normals.push(*normal);
uvs.push(*uv);
}
let mut mesh = Mesh::new(PrimitiveTopology::TriangleList);
mesh.set_indices(Some(indices));
mesh.insert_attribute(Mesh::ATTRIBUTE_POSITION, positions);
mesh.insert_attribute(Mesh::ATTRIBUTE_NORMAL, normals);
mesh.insert_attribute(Mesh::ATTRIBUTE_UV_0, uvs);
// add entities to the world
// plane
commands.spawn_bundle(PbrBundle {
mesh: meshes.add(mesh),
material: materials.add(Color::rgb(0.3, 0.5, 0.3).into()),
..default()
});
// light
commands.spawn_bundle(PointLightBundle {
point_light: PointLight {
intensity: 1500.0,
shadows_enabled: true,
..default()
},
transform: Transform::from_xyz(4.0, 8.0, 4.0),
..default()
});
// camera
commands.spawn_bundle(PerspectiveCameraBundle {
transform: Transform::from_xyz(-2.0, 2.5, 5.0)
.looking_at(Vec3::ZERO, Vec3::Y),
..default()
});
}