064e5e48b4
# Objective `Entity::PLACEHOLDER` acts as a magic number that will *probably* never really exist, but it certainly could. And, `Entity` has a niche, so the only reason to use `PLACEHOLDER` is as an alternative to `MaybeUninit` that trades safety risks for logic risks. As a result, bevy has generally advised against using `PLACEHOLDER`, but we still use if for a lot internally. This pr starts removing internal uses of it, starting from observers. ## Solution Change all trigger target related types from `Entity` to `Option<Entity>` Small migration guide to come. ## Testing CI ## Future Work This turned a lot of code from ```rust trigger.target() ``` to ```rust trigger.target().unwrap() ``` The extra panic is no worse than before; it's just earlier than panicking after passing the placeholder to something else. But this is kinda annoying. I would like to add a `TriggerMode` or something to `Event` that would restrict what kinds of targets can be used for that event. Many events like `Removed` etc, are always triggered with a target. We can make those have a way to assume Some, etc. But I wanted to save that for a future pr.
94 lines
3.3 KiB
Rust
94 lines
3.3 KiB
Rust
//! Showcases how to change the material of a `Scene` spawned from a Gltf
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use bevy::{
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app::{App, PluginGroup, Startup},
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asset::{AssetServer, Assets},
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audio::AudioPlugin,
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color::{palettes, Color},
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gltf::GltfAssetLabel,
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math::{Dir3, Vec3},
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pbr::{DirectionalLight, MeshMaterial3d, StandardMaterial},
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prelude::{Camera3d, Children, Commands, Component, Query, Res, ResMut, Transform, Trigger},
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scene::{SceneInstanceReady, SceneRoot},
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DefaultPlugins,
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};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins.build().disable::<AudioPlugin>())
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.add_systems(Startup, setup_scene)
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.add_observer(change_material)
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.run();
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}
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/// This is added to a [`SceneRoot`] and will cause the [`StandardMaterial::base_color`]
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/// of all materials to be overwritten
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#[derive(Component)]
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struct ColorOverride(Color);
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fn setup_scene(mut commands: Commands, asset_server: Res<AssetServer>) {
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commands.spawn((
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Camera3d::default(),
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Transform::from_xyz(0., 1., 2.5).looking_at(Vec3::new(0., 0.25, 0.), Dir3::Y),
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));
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commands.spawn((
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DirectionalLight::default(),
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Transform::from_xyz(0., 1., 0.25).looking_at(Vec3::ZERO, Dir3::Y),
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));
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// FlightHelmet handle
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let flight_helmet = asset_server
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.load(GltfAssetLabel::Scene(0).from_asset("models/FlightHelmet/FlightHelmet.gltf"));
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// This model will keep its original materials
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commands.spawn(SceneRoot(flight_helmet.clone()));
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// This model will be tinted red
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commands.spawn((
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SceneRoot(flight_helmet.clone()),
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Transform::from_xyz(-1.25, 0., 0.),
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ColorOverride(palettes::tailwind::RED_300.into()),
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));
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// This model will be tinted green
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commands.spawn((
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SceneRoot(flight_helmet),
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Transform::from_xyz(1.25, 0., 0.),
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ColorOverride(palettes::tailwind::GREEN_300.into()),
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));
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}
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fn change_material(
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trigger: Trigger<SceneInstanceReady>,
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mut commands: Commands,
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children: Query<&Children>,
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color_override: Query<&ColorOverride>,
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mesh_materials: Query<&MeshMaterial3d<StandardMaterial>>,
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mut asset_materials: ResMut<Assets<StandardMaterial>>,
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) {
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// Get the `ColorOverride` of the entity, if it does not have a color override, skip
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let Ok(color_override) = color_override.get(trigger.target().unwrap()) else {
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return;
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};
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// Iterate over all children recursively
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for descendants in children.iter_descendants(trigger.target().unwrap()) {
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// Get the material of the descendant
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if let Some(material) = mesh_materials
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.get(descendants)
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.ok()
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.and_then(|id| asset_materials.get_mut(id.id()))
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{
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// Create a copy of the material and override base color
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// If you intend on creating multiple models with the same tint, it
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// is best to cache the handle somewhere, as having multiple materials
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// that are identical is expensive
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let mut new_material = material.clone();
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new_material.base_color = color_override.0;
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// Override `MeshMaterial3d` with new material
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commands
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.entity(descendants)
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.insert(MeshMaterial3d(asset_materials.add(new_material)));
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}
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}
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}
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