plugin.rs

use crate::pipeline::{CollisionEvent, ContactForceEvent};
use crate::prelude::*;
use crate::reflect::{IntegrationParametersWrapper, SpringCoefficientsWrapper};
use bevy::app::DynEq;
use bevy::ecs::{
    intern::Interned,
    schedule::{IntoScheduleConfigs, ScheduleConfigs, ScheduleLabel},
    system::{ScheduleSystem, SystemParamItem},
};
use bevy::platform::collections::HashSet;
use bevy::{prelude::*, transform::TransformSystems};
use rapier::dynamics::IntegrationParameters;
use std::marker::PhantomData;

use super::context::DefaultRapierContext;

#[cfg(doc)]
use crate::plugin::context::systemparams::RapierContext;

/// No specific user-data is associated to the hooks.
pub type NoUserData = ();

/// A plugin responsible for setting up a full Rapier physics simulation pipeline and resources.
///
/// This will automatically setup all the resources needed to run a physics simulation with the
/// Rapier physics engine.
pub struct RapierPhysicsPlugin<PhysicsHooks = ()> {
    schedule: Interned<dyn ScheduleLabel>,
    default_system_setup: bool,
    /// Read during [`RapierPhysicsPlugin::build()`],
    /// to help initializing [`RapierContextInitialization`] resource.
    /// This will be ignored if that resource already exists.
    default_world_setup: RapierContextInitialization,
    /// Controls whether given `PhysicsSets` systems are injected into the scheduler.
    ///
    /// This is useful to opt out of default plugin behaviour, for example if you need to reorganize
    /// the systems in different schedules.
    ///
    /// If passing an empty set, the plugin will still add the Physics Sets to the plugin schedule,
    /// but no systems will be added automatically.
    enabled_physics_schedules: HashSet<PhysicsSet>,
    _phantom: PhantomData<PhysicsHooks>,
}

impl<PhysicsHooks> RapierPhysicsPlugin<PhysicsHooks>
where
    PhysicsHooks: 'static + BevyPhysicsHooks,
    for<'w, 's> SystemParamItem<'w, 's, PhysicsHooks>: BevyPhysicsHooks,
{
    /// Specifies a scale ratio between the physics world and the bevy transforms.
    ///
    /// This affects the size of every elements in the physics engine, by multiplying
    /// all the length-related quantities by the `length_unit` factor. This should
    /// likely always be 1.0 in 3D. In 2D, this is useful to specify a "pixels-per-meter"
    /// conversion ratio.
    pub fn with_length_unit(mut self, length_unit: f32) -> Self {
        self.default_world_setup =
            RapierContextInitialization::default_with_length_unit(length_unit);
        self
    }

    /// Specifies a default world initialization strategy.
    ///
    /// The default is to initialize a [`RapierContext`] with a length unit of 1.
    pub fn with_custom_initialization(
        mut self,
        default_world_initialization: RapierContextInitialization,
    ) -> Self {
        self.default_world_setup = default_world_initialization;
        self
    }

    /// Specifies whether the plugin should setup each of its [`PhysicsSet`]
    /// (`true`), or if the user will set them up later (`false`).
    ///
    /// The default value is `true`.
    pub fn with_default_system_setup(mut self, default_system_setup: bool) -> Self {
        self.default_system_setup = default_system_setup;
        self
    }

    /// Specifies how many pixels on the 2D canvas equal one meter on the physics world.
    ///
    /// This conversion unit assumes that the 2D camera uses an unscaled projection.
    #[cfg(feature = "dim2")]
    pub fn pixels_per_meter(pixels_per_meter: f32) -> Self {
        Self {
            default_system_setup: true,
            default_world_setup: RapierContextInitialization::default_with_length_unit(
                pixels_per_meter,
            ),
            ..default()
        }
    }

    /// Controls whether given `PhysicsSets` systems are injected into the scheduler.
    ///
    /// This is useful to opt out of default plugin behaviour, for example if you need to reorganize
    /// the systems in different schedules.
    ///
    /// If passing an empty set, the plugin will still add the Physics Sets to the plugin schedule,
    /// but no systems will be added automatically.
    pub fn with_physics_sets_systems(
        mut self,
        enabled_physics_schedules: HashSet<PhysicsSet>,
    ) -> Self {
        self.enabled_physics_schedules = enabled_physics_schedules;
        self
    }

    /// Adds the physics systems to the `FixedUpdate` schedule rather than `PostUpdate`.
    pub fn in_fixed_schedule(self) -> Self {
        self.in_schedule(FixedUpdate)
    }

    /// Adds the physics systems to the provided schedule rather than `PostUpdate`.
    pub fn in_schedule(mut self, schedule: impl ScheduleLabel) -> Self {
        self.schedule = schedule.intern();
        self
    }

    /// Provided for use when staging systems outside of this plugin using
    /// [`with_default_system_setup(false)`](Self::with_default_system_setup).
    /// See [`PhysicsSet`] for a description of these systems.
    pub fn get_systems(set: PhysicsSet) -> ScheduleConfigs<ScheduleSystem> {
        match set {
            PhysicsSet::SyncBackend => (
                (
                    // Initialize the rapier configuration.
                    // A good candidate for required component or hook components.
                    // The configuration is needed for following systems, so it should be chained.
                    setup_rapier_configuration,
                    // Run the character controller before the manual transform propagation.
                    systems::update_character_controls,
                )
                    .chain()
                    .in_set(PhysicsSet::SyncBackend),
                // Run Bevy transform propagation additionally to sync [`GlobalTransform`]
                (
                    bevy::transform::systems::sync_simple_transforms,
                    bevy::transform::systems::propagate_parent_transforms,
                )
                    .chain()
                    .in_set(RapierTransformPropagateSet),
                (
                    (
                        systems::on_add_entity_with_parent,
                        systems::on_change_context,
                        systems::sync_removals,
                        #[cfg(all(feature = "dim3", feature = "async-collider"))]
                        systems::init_async_scene_colliders,
                        #[cfg(all(feature = "dim3", feature = "async-collider"))]
                        systems::init_async_colliders,
                        systems::init_rigid_bodies,
                        systems::init_colliders,
                        systems::init_joints,
                    )
                        .chain()
                        .in_set(PhysicsSet::SyncBackend),
                    (
                        (
                            systems::apply_scale.in_set(RapierBevyComponentApply),
                            systems::apply_collider_user_changes.in_set(RapierBevyComponentApply),
                        )
                            .chain(),
                        systems::apply_joint_user_changes.in_set(RapierBevyComponentApply),
                    ),
                    // TODO: joints and colliders might be parallelizable.
                    systems::apply_initial_rigid_body_impulses.in_set(RapierBevyComponentApply),
                    systems::apply_rigid_body_user_changes.in_set(RapierBevyComponentApply),
                )
                    .chain(),
            )
                .chain()
                .into_configs(),
            PhysicsSet::StepSimulation => (systems::step_simulation::<PhysicsHooks>)
                .in_set(PhysicsSet::StepSimulation)
                .into_configs(),
            PhysicsSet::Writeback => (
                systems::update_colliding_entities,
                systems::writeback_rigid_bodies,
                // Each writeback write to different properties.
                systems::writeback_mass_properties.ambiguous_with(systems::writeback_rigid_bodies),
            )
                .in_set(PhysicsSet::Writeback)
                .into_configs(),
        }
    }
}

/// A set for rapier's copying bevy_rapier's Bevy components back into rapier.
#[derive(Debug, Hash, PartialEq, Eq, Clone, SystemSet)]
pub struct RapierBevyComponentApply;

/// A set for rapier's copy of Bevy's transform propagation systems.
///
/// See [`TransformSystems`](bevy::transform::TransformSystems::Propagate).
#[derive(Debug, Hash, PartialEq, Eq, Clone, SystemSet)]
pub struct RapierTransformPropagateSet;

impl<PhysicsHooksSystemParam> Default for RapierPhysicsPlugin<PhysicsHooksSystemParam> {
    fn default() -> Self {
        Self {
            schedule: PostUpdate.intern(),
            default_system_setup: true,
            default_world_setup: Default::default(),
            enabled_physics_schedules: HashSet::from_iter([
                PhysicsSet::SyncBackend,
                PhysicsSet::StepSimulation,
                PhysicsSet::Writeback,
            ]),
            _phantom: PhantomData,
        }
    }
}

/// [`SystemSet`] for each phase of the plugin.
#[derive(SystemSet, Debug, Hash, PartialEq, Eq, Clone)]
pub enum PhysicsSet {
    /// This set runs the systems responsible for synchronizing (and
    /// initializing) backend data structures with current component state.
    /// These systems typically run at the after [`Update`].
    SyncBackend,
    /// The systems responsible for advancing the physics simulation, and
    /// updating the internal state for scene queries.
    /// These systems typically run immediately after [`PhysicsSet::SyncBackend`].
    StepSimulation,
    /// The systems responsible for updating
    /// [`crate::geometry::CollidingEntities`] and writing
    /// the result of the last simulation step into our `bevy_rapier`
    /// components and the [`GlobalTransform`] component.
    /// These systems typically run immediately after [`PhysicsSet::StepSimulation`].
    Writeback,
}

impl<PhysicsHooks> Plugin for RapierPhysicsPlugin<PhysicsHooks>
where
    PhysicsHooks: 'static + BevyPhysicsHooks,
    for<'w, 's> SystemParamItem<'w, 's, PhysicsHooks>: BevyPhysicsHooks,
{
    fn build(&self, app: &mut App) {
        // Register components as reflectable.
        app.register_type::<RigidBody>()
            .register_type::<Velocity>()
            .register_type::<AdditionalMassProperties>()
            .register_type::<MassProperties>()
            .register_type::<LockedAxes>()
            .register_type::<ExternalForce>()
            .register_type::<ExternalImpulse>()
            .register_type::<Sleeping>()
            .register_type::<Damping>()
            .register_type::<Dominance>()
            .register_type::<Ccd>()
            .register_type::<SoftCcd>()
            .register_type::<GravityScale>()
            .register_type::<CollidingEntities>()
            .register_type::<Sensor>()
            .register_type::<Friction>()
            .register_type::<Restitution>()
            .register_type::<CollisionGroups>()
            .register_type::<SolverGroups>()
            .register_type::<ContactForceEventThreshold>()
            .register_type::<ContactSkin>()
            .register_type::<Group>()
            .register_type::<RapierContextEntityLink>()
            .register_type::<RapierConfiguration>()
            .register_type::<SimulationToRenderTime>()
            .register_type::<DefaultRapierContext>()
            .register_type::<RapierContextInitialization>()
            .register_type::<SpringCoefficientsWrapper>();

        app.insert_resource(Messages::<CollisionEvent>::default())
            .insert_resource(Messages::<ContactForceEvent>::default())
            .insert_resource(Messages::<MassModifiedEvent>::default());
        let default_world_init = app.world().get_resource::<RapierContextInitialization>();
        if let Some(world_init) = default_world_init {
            log::warn!("RapierPhysicsPlugin added but a `RapierContextInitialization` resource was already existing.\
            This might overwrite previous configuration made via `RapierPhysicsPlugin::with_custom_initialization`\
            or `RapierPhysicsPlugin::with_length_unit`.
            The following resource will be used: {world_init:?}");
        } else {
            app.insert_resource(self.default_world_setup.clone());
        }

        app.add_systems(
            PreStartup,
            (insert_default_context, setup_rapier_configuration).chain(),
        );

        // These *must* be in the main schedule currently so that they do not miss events.
        // See test `test_sync_removal` for an example of this.
        if self.schedule != PostUpdate.intern() {
            app.add_systems(
                PostUpdate,
                (systems::sync_removals,).before(TransformSystems::Propagate),
            );
        }

        // Add each set as necessary
        if self.default_system_setup {
            app.configure_sets(
                self.schedule,
                (
                    PhysicsSet::SyncBackend,
                    PhysicsSet::StepSimulation,
                    PhysicsSet::Writeback,
                )
                    .chain()
                    .before(TransformSystems::Propagate),
            );
            app.configure_sets(
                self.schedule,
                RapierTransformPropagateSet.in_set(PhysicsSet::SyncBackend),
            );
            app.configure_sets(
                self.schedule,
                RapierBevyComponentApply.in_set(PhysicsSet::SyncBackend),
            );
            let mut add_systems_if_enabled = |physics_set: PhysicsSet| {
                if self.enabled_physics_schedules.contains(&physics_set) {
                    app.add_systems(self.schedule, Self::get_systems(physics_set));
                }
            };
            add_systems_if_enabled(PhysicsSet::SyncBackend);
            add_systems_if_enabled(PhysicsSet::Writeback);
            add_systems_if_enabled(PhysicsSet::StepSimulation);

            app.init_resource::<TimestepMode>();

            // Warn user if the timestep mode isn't in Fixed
            if self.schedule.dyn_eq(&FixedUpdate as &dyn DynEq) {
                let config = app.world_mut().resource::<TimestepMode>();
                match config {
                    TimestepMode::Fixed { .. } => {}
                    mode => {
                        log::warn!("TimestepMode is set to `{mode:?}`, it is recommended to use `TimestepMode::Fixed` if you have the physics in `FixedUpdate`");
                    }
                }
            }
        }
    }

    fn finish(&self, _app: &mut App) {
        #[cfg(all(feature = "dim3", feature = "async-collider"))]
        {
            use bevy::{asset::AssetPlugin, mesh::MeshPlugin, scene::ScenePlugin};
            if !_app.is_plugin_added::<AssetPlugin>() {
                _app.add_plugins(AssetPlugin::default());
            }
            if !_app.is_plugin_added::<MeshPlugin>() {
                _app.add_plugins(MeshPlugin);
            }
            if !_app.is_plugin_added::<ScenePlugin>() {
                _app.add_plugins(ScenePlugin);
            }
        }
    }
}

/// Specifies a default configuration for the default [`RapierContext`]
///
/// Designed to be passed as parameter to [`RapierPhysicsPlugin::with_custom_initialization`].
#[derive(Resource, Debug, Reflect, Clone)]
pub enum RapierContextInitialization {
    /// [`RapierPhysicsPlugin`] will not spawn any entity containing [`RapierContextSimulation`] automatically.
    ///
    /// You are responsible for creating a [`RapierContextSimulation`],
    /// before spawning any rapier entities (rigidbodies, colliders, joints).
    ///
    /// You might be interested in adding [`DefaultRapierContext`] to the created physics context.
    NoAutomaticRapierContext,
    /// [`RapierPhysicsPlugin`] will spawn an entity containing a [`RapierContextSimulation`]
    /// automatically during [`PreStartup`], with the [`DefaultRapierContext`] marker component.
    InitializeDefaultRapierContext {
        /// Integration parameters component which will be added to the default rapier context.
        #[reflect(remote = IntegrationParametersWrapper)]
        integration_parameters: IntegrationParameters,
        /// Rapier configuration component which will be added to the default rapier context.
        rapier_configuration: RapierConfiguration,
    },
}

impl Default for RapierContextInitialization {
    fn default() -> Self {
        Self::default_with_length_unit(1f32)
    }
}

impl RapierContextInitialization {
    /// Configures rapier with the specified length unit.
    ///
    /// See the documentation of [`IntegrationParameters::length_unit`] for additional details
    /// on that argument.
    ///
    /// The default gravity is automatically scaled by that length unit.
    pub fn default_with_length_unit(length_unit: f32) -> Self {
        let integration_parameters = IntegrationParameters {
            length_unit,
            ..default()
        };

        RapierContextInitialization::InitializeDefaultRapierContext {
            integration_parameters,
            rapier_configuration: RapierConfiguration::new(length_unit),
        }
    }
}

pub fn insert_default_context(
    mut commands: Commands,
    initialization_data: Res<RapierContextInitialization>,
) {
    match initialization_data.as_ref() {
        RapierContextInitialization::NoAutomaticRapierContext => {}
        RapierContextInitialization::InitializeDefaultRapierContext {
            integration_parameters,
            rapier_configuration,
        } => {
            commands.spawn((
                Name::new("Rapier Context"),
                RapierContextSimulation {
                    integration_parameters: *integration_parameters,
                    ..RapierContextSimulation::default()
                },
                *rapier_configuration,
                DefaultRapierContext,
            ));
        }
    }
}

pub fn setup_rapier_configuration(
    mut commands: Commands,
    rapier_context: Query<(Entity, &RapierContextSimulation), Without<RapierConfiguration>>,
) {
    for (e, rapier_context) in rapier_context.iter() {
        commands.entity(e).insert(RapierConfiguration::new(
            rapier_context.integration_parameters.length_unit,
        ));
    }
}

#[cfg(test)]
mod test {

    use bevy::{
        ecs::schedule::{NodeId, Stepping},
        prelude::Component,
        time::{TimePlugin, TimeUpdateStrategy},
    };
    use rapier::{data::Index, dynamics::RigidBodyHandle};

    use crate::{plugin::context::*, plugin::*, prelude::*};

    #[cfg(feature = "dim3")]
    fn cuboid(hx: Real, hy: Real, hz: Real) -> Collider {
        Collider::cuboid(hx, hy, hz)
    }
    #[cfg(feature = "dim2")]
    fn cuboid(hx: Real, hy: Real, _hz: Real) -> Collider {
        Collider::cuboid(hx, hy)
    }

    #[derive(Component)]
    pub struct TestMarker;

    #[test]
    pub fn hierarchy_link_propagation() {
        return main();

        use bevy::prelude::*;

        fn run_test(app: &mut App) {
            app.insert_resource(TimeUpdateStrategy::ManualDuration(
                std::time::Duration::from_secs_f32(1f32 / 60f32),
            ));

            app.add_systems(Update, setup_physics);

            app.finish();

            let mut stepping = Stepping::new();

            app.update();

            stepping
                .add_schedule(PostUpdate)
                .add_schedule(Update)
                .enable()
                .set_breakpoint(PostUpdate, systems::on_add_entity_with_parent)
                .set_breakpoint(PostUpdate, systems::init_rigid_bodies)
                .set_breakpoint(PostUpdate, systems::on_change_context)
                .set_breakpoint(PostUpdate, systems::sync_removals)
                .set_breakpoint(Update, setup_physics);

            app.insert_resource(stepping);

            let mut stepping = app.world_mut().resource_mut::<Stepping>();
            // Advancing once to get the context.
            stepping.continue_frame();
            app.update();
            // arbitrary hardcoded amount to run the simulation for a few frames.
            // This test uses stepping so the actual amount of frames is this `number / breakpoints`
            for _ in 0..20 {
                let world = app.world_mut();
                let stepping = world.resource_mut::<Stepping>();
                if let Some(cursor) = &stepping.cursor() {
                    let system = world
                        .resource::<Schedules>()
                        .get(cursor.0)
                        .unwrap()
                        .systems()
                        .unwrap()
                        .find(|s| NodeId::System(s.0) == cursor.1)
                        .unwrap();
                    println!(
                        "next system: {}",
                        system
                            .1
                            .name()
                            .to_string()
                            .split_terminator("::")
                            .last()
                            .unwrap()
                    );
                } else {
                    println!("no cursor, new frame!");
                }
                let mut stepping = world.resource_mut::<Stepping>();
                stepping.continue_frame();
                app.update();

                let rigidbody_set = app
                    .world_mut()
                    .query::<&RapierRigidBodySet>()
                    .single(app.world())
                    .unwrap();

                println!("{:?}", &rigidbody_set.entity2body);
            }
            let rigidbody_set = app
                .world_mut()
                .query::<&RapierRigidBodySet>()
                .single(app.world())
                .unwrap();

            assert_eq!(
                rigidbody_set.entity2body.iter().next().unwrap().1,
                // assert the generation is 0, that means we didn't modify it twice (due to change world detection)
                &RigidBodyHandle(Index::from_raw_parts(0, 0))
            );
        }

        fn main() {
            let mut app = App::new();
            app.add_plugins((
                TransformPlugin,
                TimePlugin,
                RapierPhysicsPlugin::<NoUserData>::default(),
            ));
            run_test(&mut app);
        }

        pub fn setup_physics(mut commands: Commands, mut counter: Local<i32>) {
            // run on the 3rd iteration: I believe current logic is:
            // - 1st is to setup bevy internals
            // - 2nd is to wait for having stepping enabled, as I couldnt get it to work for the first update.
            // - 3rd, we're looking to test adding a rapier entity while playing, opposed to a Startup function,
            //   which most examples are focused on.
            let run_at = 3;
            if *counter == run_at {
                return;
            }
            *counter += 1;
            if *counter < run_at {
                return;
            }

            commands.spawn((
                Transform::from_xyz(0.0, 13.0, 0.0),
                RigidBody::Dynamic,
                cuboid(0.5, 0.5, 0.5),
                TestMarker,
            ));
        }
    }

    #[test]
    pub fn test_sync_removal() {
        return main();

        use bevy::prelude::*;

        fn run_test(app: &mut App) {
            app.insert_resource(TimeUpdateStrategy::ManualDuration(
                std::time::Duration::from_secs_f32(1f32 / 60f32),
            ));
            app.insert_resource(Time::<Fixed>::from_hz(20.0));

            app.add_systems(Startup, setup_physics);
            app.add_systems(Update, remove_rapier_entity);
            app.add_systems(FixedUpdate, || println!("Fixed Update"));
            app.add_systems(Update, || println!("Update"));
            app.finish();
            // startup
            app.update();
            // normal updates starting
            // render only
            app.update();
            app.update();
            // render + physics
            app.update();

            let mut context_query = app.world_mut().query::<RapierContext>();
            let context = context_query.single(app.world()).unwrap();
            assert_eq!(context.rigidbody_set.entity2body.len(), 1);

            // render only + remove entities
            app.update();
            // Fixed Update hasn´t run yet, so it's a risk of not having caught the bevy removed event, which will be cleaned next frame.

            let mut context_query = app.world_mut().query::<RapierContext>();
            let context = context_query.single(app.world()).unwrap();

            println!("{:?}", &context.rigidbody_set.entity2body);
            assert_eq!(context.rigidbody_set.entity2body.len(), 0);
        }

        fn main() {
            let mut app = App::new();
            app.add_plugins((
                TransformPlugin,
                TimePlugin,
                RapierPhysicsPlugin::<NoUserData>::default().in_fixed_schedule(),
            ));
            run_test(&mut app);
        }

        pub fn setup_physics(mut commands: Commands) {
            commands.spawn((
                Transform::from_xyz(0.0, 13.0, 0.0),
                RigidBody::Dynamic,
                cuboid(0.5, 0.5, 0.5),
                TestMarker,
            ));
            println!("spawned rapier entity");
        }
        pub fn remove_rapier_entity(
            mut commands: Commands,
            to_remove: Query<Entity, With<TestMarker>>,
            mut counter: Local<i32>,
        ) {
            *counter += 1;
            if *counter != 5 {
                return;
            }
            println!("removing rapier entity");
            for e in &to_remove {
                commands.entity(e).despawn();
            }
        }
    }

    #[test]
    fn parent_child() {
        return main();

        use bevy::prelude::*;

        fn main() {
            let mut app = App::new();
            app.add_plugins((
                TransformPlugin,
                TimePlugin,
                RapierPhysicsPlugin::<NoUserData>::default().in_fixed_schedule(),
            ));
            run_test(&mut app);
        }

        fn run_test(app: &mut App) {
            app.insert_resource(TimeUpdateStrategy::ManualDuration(
                std::time::Duration::from_secs_f32(1f32 / 60f32),
            ));
            app.add_systems(Startup, init_rapier_configuration);
            app.add_systems(Startup, setup_physics);

            app.finish();
            for _ in 0..100 {
                app.update();
            }

            let mut context_query = app.world_mut().query::<RapierContext>();
            let context = context_query.single(app.world()).unwrap();

            println!("{:#?}", &context.rigidbody_set.bodies);
        }

        pub fn init_rapier_configuration(
            mut config: Query<&mut RapierConfiguration, With<DefaultRapierContext>>,
        ) {
            let mut config = config.single_mut().unwrap();
            *config = RapierConfiguration {
                force_update_from_transform_changes: true,
                ..RapierConfiguration::new(1f32)
            };
        }

        pub fn setup_physics(mut commands: Commands) {
            let parent = commands
                .spawn(Transform::from_scale(Vec3::splat(5f32)))
                .id();
            let mut entity_commands = commands.spawn((
                Collider::ball(1f32),
                Transform::from_translation(Vec3::new(200f32, 100f32, 3f32)),
                RigidBody::Fixed,
            ));
            entity_commands.insert(ChildOf(parent));
        }
    }

    #[test]
    fn initial_scale() {
        return main();

        use bevy::prelude::*;

        fn main() {
            let mut app = App::new();
            app.add_plugins((
                TransformPlugin,
                TimePlugin,
                RapierPhysicsPlugin::<NoUserData>::default().in_fixed_schedule(),
            ));
            run_test(&mut app);
        }

        fn run_test(app: &mut App) {
            app.insert_resource(TimeUpdateStrategy::ManualDuration(
                std::time::Duration::from_secs_f32(1f32 / 60f32),
            ));
            app.add_systems(Update, setup_physics.run_if(run_once));

            app.finish();

            // Running startup
            app.update();
            // Running first physics setup, initializes colliders and scaling.
            app.update();

            let collider = app
                .world_mut()
                .query::<&Collider>()
                .single(app.world())
                .unwrap();
            approx::assert_relative_eq!(collider.scale, Vect::splat(0.1), epsilon = 1.0e-5);

            let mut context_query = app.world_mut().query::<RapierContext>();
            let context = context_query.single(app.world()).unwrap();
            let physics_ball_radius = context
                .colliders
                .colliders
                .iter()
                .next()
                .unwrap()
                .1
                .shape()
                .as_ball()
                .unwrap()
                .radius;
            approx::assert_relative_eq!(physics_ball_radius, 0.1, epsilon = 0.1);
        }

        pub fn setup_physics(mut commands: Commands) {
            commands.spawn((
                Transform::from_translation(Vec3::new(-0.2, 0.0, 0.0)).with_scale(Vec3::splat(0.1)),
                Collider::ball(1.0),
            ));
        }
    }
}