eaeba0866d
# Objective Fixes #4697. Hierarchical propagation of properties, currently only Transform -> GlobalTransform, can be a very expensive operation. Transform propagation is a strict dependency for anything positioned in world-space. In large worlds, this can take quite a bit of time, so limiting it to a single thread can result in poor CPU utilization as it bottlenecks the rest of the frame's systems. ## Solution - Move transforms without a parent or a child (free-floating (Global)Transform) entities into a separate parallel system. - Chunk the hierarchy based on the root entities and process it in parallel with `Query::par_for_each_mut`. - Utilize the hierarchy's specific properties introduced in #4717 to allow for safe use of `Query::get_unchecked` on multiple threads. Assuming each child is unique in the hierarchy, it is impossible to have an aliased `&mut GlobalTransform` so long as we verify that the parent for a child is the same one propagated from. --- ## Changelog Removed: `transform_propagate_system` is no longer `pub`.
110 lines
4.0 KiB
Rust
110 lines
4.0 KiB
Rust
#![warn(missing_docs)]
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#![warn(clippy::undocumented_unsafe_blocks)]
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#![doc = include_str!("../README.md")]
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/// The basic components of the transform crate
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pub mod components;
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mod systems;
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#[doc(hidden)]
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pub mod prelude {
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#[doc(hidden)]
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pub use crate::{components::*, TransformBundle, TransformPlugin};
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}
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use bevy_app::prelude::*;
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use bevy_ecs::prelude::*;
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use bevy_hierarchy::ValidParentCheckPlugin;
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use prelude::{GlobalTransform, Transform};
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/// A [`Bundle`] of the [`Transform`] and [`GlobalTransform`]
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/// [`Component`](bevy_ecs::component::Component)s, which describe the position of an entity.
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///
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/// * To place or move an entity, you should set its [`Transform`].
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/// * To get the global transform of an entity, you should get its [`GlobalTransform`].
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/// * For transform hierarchies to work correctly, you must have both a [`Transform`] and a [`GlobalTransform`].
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/// * You may use the [`TransformBundle`] to guarantee this.
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///
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/// ## [`Transform`] and [`GlobalTransform`]
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///
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/// [`Transform`] is the position of an entity relative to its parent position, or the reference
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/// frame if it doesn't have a parent.
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///
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/// [`GlobalTransform`] is the position of an entity relative to the reference frame.
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///
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/// [`GlobalTransform`] is updated from [`Transform`] in the systems labeled
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/// [`TransformPropagate`](crate::TransformSystem::TransformPropagate).
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///
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/// This system runs in stage [`CoreStage::PostUpdate`](crate::CoreStage::PostUpdate). If you
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/// update the [`Transform`] of an entity in this stage or after, you will notice a 1 frame lag
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/// before the [`GlobalTransform`] is updated.
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#[derive(Bundle, Clone, Copy, Debug, Default)]
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pub struct TransformBundle {
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/// The transform of the entity.
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pub local: Transform,
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/// The global transform of the entity.
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pub global: GlobalTransform,
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}
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impl TransformBundle {
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/// An identity [`TransformBundle`] with no translation, rotation, and a scale of 1 on all axes.
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pub const IDENTITY: Self = TransformBundle {
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local: Transform::IDENTITY,
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global: GlobalTransform::IDENTITY,
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};
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/// Creates a new [`TransformBundle`] from a [`Transform`].
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///
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/// This initializes [`GlobalTransform`] as identity, to be updated later by the
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/// [`CoreStage::PostUpdate`](crate::CoreStage::PostUpdate) stage.
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#[inline]
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pub const fn from_transform(transform: Transform) -> Self {
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TransformBundle {
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local: transform,
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..Self::IDENTITY
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}
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}
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}
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impl From<Transform> for TransformBundle {
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#[inline]
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fn from(transform: Transform) -> Self {
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Self::from_transform(transform)
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}
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}
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/// Label enum for the systems relating to transform propagation
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#[derive(Debug, Hash, PartialEq, Eq, Clone, SystemLabel)]
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pub enum TransformSystem {
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/// Propagates changes in transform to children's [`GlobalTransform`](crate::components::GlobalTransform)
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TransformPropagate,
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}
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/// The base plugin for handling [`Transform`] components
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#[derive(Default)]
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pub struct TransformPlugin;
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impl Plugin for TransformPlugin {
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fn build(&self, app: &mut App) {
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app.register_type::<Transform>()
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.register_type::<GlobalTransform>()
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.add_plugin(ValidParentCheckPlugin::<GlobalTransform>::default())
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// add transform systems to startup so the first update is "correct"
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.add_startup_system_to_stage(
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StartupStage::PostStartup,
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systems::sync_simple_transforms.label(TransformSystem::TransformPropagate),
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)
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.add_startup_system_to_stage(
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StartupStage::PostStartup,
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systems::propagate_transforms.label(TransformSystem::TransformPropagate),
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)
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.add_system_to_stage(
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CoreStage::PostUpdate,
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systems::sync_simple_transforms.label(TransformSystem::TransformPropagate),
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)
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.add_system_to_stage(
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CoreStage::PostUpdate,
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systems::propagate_transforms.label(TransformSystem::TransformPropagate),
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);
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}
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}
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