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

custom_skinned_mesh/
custom_skinned_mesh.rs
