custom_skinned_mesh/
custom_skinned_mesh.rs

1//! Skinned mesh example with mesh and joints data defined in code.
2//! Example taken from <https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_019_SimpleSkin.md>
3
4use std::f32::consts::*;
5
6use bevy::{
7    math::ops,
8    prelude::*,
9    render::{
10        mesh::{
11            skinning::{SkinnedMesh, SkinnedMeshInverseBindposes},
12            Indices, PrimitiveTopology, VertexAttributeValues,
13        },
14        render_asset::RenderAssetUsages,
15    },
16};
17use rand::{Rng, SeedableRng};
18use rand_chacha::ChaCha8Rng;
19
20fn main() {
21    App::new()
22        .add_plugins(DefaultPlugins)
23        .insert_resource(AmbientLight {
24            brightness: 3000.0,
25            ..default()
26        })
27        .add_systems(Startup, setup)
28        .add_systems(Update, joint_animation)
29        .run();
30}
31
32/// Used to mark a joint to be animated in the [`joint_animation`] system.
33#[derive(Component)]
34struct AnimatedJoint(isize);
35
36/// Construct a mesh and a skeleton with 2 joints for that mesh,
37///   and mark the second joint to be animated.
38/// It is similar to the scene defined in `models/SimpleSkin/SimpleSkin.gltf`
39fn setup(
40    mut commands: Commands,
41    asset_server: Res<AssetServer>,
42    mut meshes: ResMut<Assets<Mesh>>,
43    mut materials: ResMut<Assets<StandardMaterial>>,
44    mut skinned_mesh_inverse_bindposes_assets: ResMut<Assets<SkinnedMeshInverseBindposes>>,
45) {
46    // Create a camera
47    commands.spawn((
48        Camera3d::default(),
49        Transform::from_xyz(2.5, 2.5, 9.0).looking_at(Vec3::ZERO, Vec3::Y),
50    ));
51
52    // Create inverse bindpose matrices for a skeleton consists of 2 joints
53    let inverse_bindposes = skinned_mesh_inverse_bindposes_assets.add(vec![
54        Mat4::from_translation(Vec3::new(-0.5, -1.0, 0.0)),
55        Mat4::from_translation(Vec3::new(-0.5, -1.0, 0.0)),
56    ]);
57
58    // Create a mesh
59    let mesh = Mesh::new(
60        PrimitiveTopology::TriangleList,
61        RenderAssetUsages::RENDER_WORLD,
62    )
63    // Set mesh vertex positions
64    .with_inserted_attribute(
65        Mesh::ATTRIBUTE_POSITION,
66        vec![
67            [0.0, 0.0, 0.0],
68            [1.0, 0.0, 0.0],
69            [0.0, 0.5, 0.0],
70            [1.0, 0.5, 0.0],
71            [0.0, 1.0, 0.0],
72            [1.0, 1.0, 0.0],
73            [0.0, 1.5, 0.0],
74            [1.0, 1.5, 0.0],
75            [0.0, 2.0, 0.0],
76            [1.0, 2.0, 0.0],
77        ],
78    )
79    // Add UV coordinates that map the left half of the texture since its a 1 x
80    // 2 rectangle.
81    .with_inserted_attribute(
82        Mesh::ATTRIBUTE_UV_0,
83        vec![
84            [0.0, 0.00],
85            [0.5, 0.00],
86            [0.0, 0.25],
87            [0.5, 0.25],
88            [0.0, 0.50],
89            [0.5, 0.50],
90            [0.0, 0.75],
91            [0.5, 0.75],
92            [0.0, 1.00],
93            [0.5, 1.00],
94        ],
95    )
96    // Set mesh vertex normals
97    .with_inserted_attribute(Mesh::ATTRIBUTE_NORMAL, vec![[0.0, 0.0, 1.0]; 10])
98    // Set mesh vertex joint indices for mesh skinning.
99    // Each vertex gets 4 indices used to address the `JointTransforms` array in the vertex shader
100    //  as well as `SkinnedMeshJoint` array in the `SkinnedMesh` component.
101    // This means that a maximum of 4 joints can affect a single vertex.
102    .with_inserted_attribute(
103        Mesh::ATTRIBUTE_JOINT_INDEX,
104        // Need to be explicit here as [u16; 4] could be either Uint16x4 or Unorm16x4.
105        VertexAttributeValues::Uint16x4(vec![
106            [0, 0, 0, 0],
107            [0, 0, 0, 0],
108            [0, 1, 0, 0],
109            [0, 1, 0, 0],
110            [0, 1, 0, 0],
111            [0, 1, 0, 0],
112            [0, 1, 0, 0],
113            [0, 1, 0, 0],
114            [0, 1, 0, 0],
115            [0, 1, 0, 0],
116        ]),
117    )
118    // Set mesh vertex joint weights for mesh skinning.
119    // Each vertex gets 4 joint weights corresponding to the 4 joint indices assigned to it.
120    // The sum of these weights should equal to 1.
121    .with_inserted_attribute(
122        Mesh::ATTRIBUTE_JOINT_WEIGHT,
123        vec![
124            [1.00, 0.00, 0.0, 0.0],
125            [1.00, 0.00, 0.0, 0.0],
126            [0.75, 0.25, 0.0, 0.0],
127            [0.75, 0.25, 0.0, 0.0],
128            [0.50, 0.50, 0.0, 0.0],
129            [0.50, 0.50, 0.0, 0.0],
130            [0.25, 0.75, 0.0, 0.0],
131            [0.25, 0.75, 0.0, 0.0],
132            [0.00, 1.00, 0.0, 0.0],
133            [0.00, 1.00, 0.0, 0.0],
134        ],
135    )
136    // Tell bevy to construct triangles from a list of vertex indices,
137    // where each 3 vertex indices form a triangle.
138    .with_inserted_indices(Indices::U16(vec![
139        0, 1, 3, 0, 3, 2, 2, 3, 5, 2, 5, 4, 4, 5, 7, 4, 7, 6, 6, 7, 9, 6, 9, 8,
140    ]));
141
142    let mesh = meshes.add(mesh);
143
144    // We're seeding the PRNG here to make this example deterministic for testing purposes.
145    // This isn't strictly required in practical use unless you need your app to be deterministic.
146    let mut rng = ChaCha8Rng::seed_from_u64(42);
147
148    for i in -5..5 {
149        // Create joint entities
150        let joint_0 = commands
151            .spawn(Transform::from_xyz(
152                i as f32 * 1.5,
153                0.0,
154                // Move quads back a small amount to avoid Z-fighting and not
155                // obscure the transform gizmos.
156                -(i as f32 * 0.01).abs(),
157            ))
158            .id();
159        let joint_1 = commands.spawn((AnimatedJoint(i), Transform::IDENTITY)).id();
160
161        // Set joint_1 as a child of joint_0.
162        commands.entity(joint_0).add_children(&[joint_1]);
163
164        // Each joint in this vector corresponds to each inverse bindpose matrix in `SkinnedMeshInverseBindposes`.
165        let joint_entities = vec![joint_0, joint_1];
166
167        // Create skinned mesh renderer. Note that its transform doesn't affect the position of the mesh.
168        commands.spawn((
169            Mesh3d(mesh.clone()),
170            MeshMaterial3d(materials.add(StandardMaterial {
171                base_color: Color::srgb(
172                    rng.gen_range(0.0..1.0),
173                    rng.gen_range(0.0..1.0),
174                    rng.gen_range(0.0..1.0),
175                ),
176                base_color_texture: Some(asset_server.load("textures/uv_checker_bw.png")),
177                ..default()
178            })),
179            SkinnedMesh {
180                inverse_bindposes: inverse_bindposes.clone(),
181                joints: joint_entities,
182            },
183        ));
184    }
185}
186
187/// Animate the joint marked with [`AnimatedJoint`] component.
188fn joint_animation(
189    time: Res<Time>,
190    mut query: Query<(&mut Transform, &AnimatedJoint)>,
191    mut gizmos: Gizmos,
192) {
193    for (mut transform, animated_joint) in &mut query {
194        match animated_joint.0 {
195            -5 => {
196                transform.rotation =
197                    Quat::from_rotation_x(FRAC_PI_2 * ops::sin(time.elapsed_secs()));
198            }
199            -4 => {
200                transform.rotation =
201                    Quat::from_rotation_y(FRAC_PI_2 * ops::sin(time.elapsed_secs()));
202            }
203            -3 => {
204                transform.rotation =
205                    Quat::from_rotation_z(FRAC_PI_2 * ops::sin(time.elapsed_secs()));
206            }
207            -2 => {
208                transform.scale.x = ops::sin(time.elapsed_secs()) + 1.0;
209            }
210            -1 => {
211                transform.scale.y = ops::sin(time.elapsed_secs()) + 1.0;
212            }
213            0 => {
214                transform.translation.x = 0.5 * ops::sin(time.elapsed_secs());
215                transform.translation.y = ops::cos(time.elapsed_secs());
216            }
217            1 => {
218                transform.translation.y = ops::sin(time.elapsed_secs());
219                transform.translation.z = ops::cos(time.elapsed_secs());
220            }
221            2 => {
222                transform.translation.x = ops::sin(time.elapsed_secs());
223            }
224            3 => {
225                transform.translation.y = ops::sin(time.elapsed_secs());
226                transform.scale.x = ops::sin(time.elapsed_secs()) + 1.0;
227            }
228            _ => (),
229        }
230        // Show transform
231        let mut axis = *transform;
232        axis.translation.x += animated_joint.0 as f32 * 1.5;
233        gizmos.axes(axis, 1.0);
234    }
235}
custom_skinned_mesh/custom_skinned_mesh.rs

custom_skinned_mesh/
custom_skinned_mesh.rs
