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//! Skinned mesh example with mesh and joints data defined in code.
//! Example taken from <https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_019_SimpleSkin.md>
use std::f32::consts::*;
use bevy::{
prelude::*,
render::{
mesh::{
skinning::{SkinnedMesh, SkinnedMeshInverseBindposes},
Indices, PrimitiveTopology, VertexAttributeValues,
},
render_asset::RenderAssetUsages,
},
};
use rand::{Rng, SeedableRng};
use rand_chacha::ChaCha8Rng;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.insert_resource(AmbientLight {
brightness: 3000.0,
..default()
})
.add_systems(Startup, setup)
.add_systems(Update, joint_animation)
.run();
}
/// Used to mark a joint to be animated in the [`joint_animation`] system.
#[derive(Component)]
struct AnimatedJoint;
/// Construct a mesh and a skeleton with 2 joints for that mesh,
/// and mark the second joint to be animated.
/// It is similar to the scene defined in `models/SimpleSkin/SimpleSkin.gltf`
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
mut skinned_mesh_inverse_bindposes_assets: ResMut<Assets<SkinnedMeshInverseBindposes>>,
) {
// Create a camera
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
..default()
});
// Create inverse bindpose matrices for a skeleton consists of 2 joints
let inverse_bindposes = skinned_mesh_inverse_bindposes_assets.add(vec![
Mat4::from_translation(Vec3::new(-0.5, -1.0, 0.0)),
Mat4::from_translation(Vec3::new(-0.5, -1.0, 0.0)),
]);
// Create a mesh
let mesh = Mesh::new(
PrimitiveTopology::TriangleList,
RenderAssetUsages::RENDER_WORLD,
)
// Set mesh vertex positions
.with_inserted_attribute(
Mesh::ATTRIBUTE_POSITION,
vec![
[0.0, 0.0, 0.0],
[1.0, 0.0, 0.0],
[0.0, 0.5, 0.0],
[1.0, 0.5, 0.0],
[0.0, 1.0, 0.0],
[1.0, 1.0, 0.0],
[0.0, 1.5, 0.0],
[1.0, 1.5, 0.0],
[0.0, 2.0, 0.0],
[1.0, 2.0, 0.0],
],
)
// Set mesh vertex normals
.with_inserted_attribute(Mesh::ATTRIBUTE_NORMAL, vec![[0.0, 0.0, 1.0]; 10])
// Set mesh vertex joint indices for mesh skinning.
// Each vertex gets 4 indices used to address the `JointTransforms` array in the vertex shader
// as well as `SkinnedMeshJoint` array in the `SkinnedMesh` component.
// This means that a maximum of 4 joints can affect a single vertex.
.with_inserted_attribute(
Mesh::ATTRIBUTE_JOINT_INDEX,
// Need to be explicit here as [u16; 4] could be either Uint16x4 or Unorm16x4.
VertexAttributeValues::Uint16x4(vec![
[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
[0, 1, 0, 0],
]),
)
// Set mesh vertex joint weights for mesh skinning.
// Each vertex gets 4 joint weights corresponding to the 4 joint indices assigned to it.
// The sum of these weights should equal to 1.
.with_inserted_attribute(
Mesh::ATTRIBUTE_JOINT_WEIGHT,
vec![
[1.00, 0.00, 0.0, 0.0],
[1.00, 0.00, 0.0, 0.0],
[0.75, 0.25, 0.0, 0.0],
[0.75, 0.25, 0.0, 0.0],
[0.50, 0.50, 0.0, 0.0],
[0.50, 0.50, 0.0, 0.0],
[0.25, 0.75, 0.0, 0.0],
[0.25, 0.75, 0.0, 0.0],
[0.00, 1.00, 0.0, 0.0],
[0.00, 1.00, 0.0, 0.0],
],
)
// Tell bevy to construct triangles from a list of vertex indices,
// where each 3 vertex indices form an triangle.
.with_inserted_indices(Indices::U16(vec![
0, 1, 3, 0, 3, 2, 2, 3, 5, 2, 5, 4, 4, 5, 7, 4, 7, 6, 6, 7, 9, 6, 9, 8,
]));
let mesh = meshes.add(mesh);
// We're seeding the PRNG here to make this example deterministic for testing purposes.
// This isn't strictly required in practical use unless you need your app to be deterministic.
let mut rng = ChaCha8Rng::seed_from_u64(42);
for i in -5..5 {
// Create joint entities
let joint_0 = commands
.spawn(TransformBundle::from(Transform::from_xyz(
i as f32 * 1.5,
0.0,
i as f32 * 0.1,
)))
.id();
let joint_1 = commands
.spawn((AnimatedJoint, TransformBundle::IDENTITY))
.id();
// Set joint_1 as a child of joint_0.
commands.entity(joint_0).push_children(&[joint_1]);
// Each joint in this vector corresponds to each inverse bindpose matrix in `SkinnedMeshInverseBindposes`.
let joint_entities = vec![joint_0, joint_1];
// Create skinned mesh renderer. Note that its transform doesn't affect the position of the mesh.
commands.spawn((
PbrBundle {
mesh: mesh.clone(),
material: materials.add(Color::srgb(
rng.gen_range(0.0..1.0),
rng.gen_range(0.0..1.0),
rng.gen_range(0.0..1.0),
)),
..default()
},
SkinnedMesh {
inverse_bindposes: inverse_bindposes.clone(),
joints: joint_entities,
},
));
}
}
/// Animate the joint marked with [`AnimatedJoint`] component.
fn joint_animation(time: Res<Time>, mut query: Query<&mut Transform, With<AnimatedJoint>>) {
for mut transform in &mut query {
transform.rotation = Quat::from_rotation_z(FRAC_PI_2 * time.elapsed_seconds().sin());
}
}