d8fa57bd7b
# Objective In #17905 we swapped to a named field on `ChildOf` to help resolve variable naming ambiguity of child vs parent (ex: `child_of.parent` clearly reads as "I am accessing the parent of the child_of relationship", whereas `child_of.0` is less clear). Unfortunately this has the side effect of making initialization less ideal. `ChildOf { parent }` reads just as well as `ChildOf(parent)`, but `ChildOf { parent: root }` doesn't read nearly as well as `ChildOf(root)`. ## Solution Move back to `ChildOf(pub Entity)` but add a `child_of.parent()` function and use it for all accesses. The downside here is that users are no longer "forced" to access the parent field with `parent` nomenclature, but I think this strikes the right balance. Take a look at the diff. I think the results provide strong evidence for this change. Initialization has the benefit of reading much better _and_ of taking up significantly less space, as many lines go from 3 to 1, and we're cutting out a bunch of syntax in some cases. Sadly I do think this should land in 0.16 as the cost of doing this _after_ the relationships migration is high.
72 lines
2.5 KiB
Rust
72 lines
2.5 KiB
Rust
//! Skinned mesh example with mesh and joints data loaded from a glTF file.
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//! Example taken from <https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_019_SimpleSkin.md>
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use std::f32::consts::*;
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use bevy::{math::ops, prelude::*, render::mesh::skinning::SkinnedMesh};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.insert_resource(AmbientLight {
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brightness: 750.0,
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..default()
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})
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.add_systems(Startup, setup)
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.add_systems(Update, joint_animation)
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.run();
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}
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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// Create a camera
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commands.spawn((
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Camera3d::default(),
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Transform::from_xyz(-2.0, 2.5, 5.0).looking_at(Vec3::new(0.0, 1.0, 0.0), Vec3::Y),
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));
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// Spawn the first scene in `models/SimpleSkin/SimpleSkin.gltf`
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commands.spawn(SceneRoot(asset_server.load(
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GltfAssetLabel::Scene(0).from_asset("models/SimpleSkin/SimpleSkin.gltf"),
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)));
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}
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/// The scene hierarchy currently looks somewhat like this:
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///
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/// ```text
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/// <Parent entity>
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/// + Mesh node (without `Mesh3d` or `SkinnedMesh` component)
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/// + Skinned mesh entity (with `Mesh3d` and `SkinnedMesh` component, created by glTF loader)
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/// + First joint
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/// + Second joint
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/// ```
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///
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/// In this example, we want to get and animate the second joint.
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/// It is similar to the animation defined in `models/SimpleSkin/SimpleSkin.gltf`.
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fn joint_animation(
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time: Res<Time>,
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children: Query<&ChildOf, With<SkinnedMesh>>,
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parents: Query<&Children>,
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mut transform_query: Query<&mut Transform>,
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) {
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// Iter skinned mesh entity
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for child_of in &children {
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// Mesh node is the parent of the skinned mesh entity.
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let mesh_node_entity = child_of.parent();
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// Get `Children` in the mesh node.
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let mesh_node_parent = parents.get(mesh_node_entity).unwrap();
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// First joint is the second child of the mesh node.
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let first_joint_entity = mesh_node_parent[1];
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// Get `Children` in the first joint.
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let first_joint_children = parents.get(first_joint_entity).unwrap();
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// Second joint is the first child of the first joint.
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let second_joint_entity = first_joint_children[0];
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// Get `Transform` in the second joint.
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let mut second_joint_transform = transform_query.get_mut(second_joint_entity).unwrap();
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second_joint_transform.rotation =
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Quat::from_rotation_z(FRAC_PI_2 * ops::sin(time.elapsed_secs()));
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}
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}
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