games/examples/sensors.rs

use bevy::{
    color::palettes::css::{BLUE, GREEN},
    render::mesh::{SphereKind, SphereMeshBuilder},
};
use bevy_rapier3d::rapier::prelude::CollisionEventFlags;
use games::*;

/// Example showing using Rapier3d to do area intersection
///
/// Have you ever wanted to detect if a character is within some bounds?
/// This shows how to do that.
fn main() {
    App::new()
        .add_plugins(BaseGamePlugin)
        .init_resource::<InsideArea>()
        .add_systems(
            Startup,
            (
                setup_physics_scene,
                setup_ui,
                position_camera.after(setup_camera),
            ),
        )
        .add_systems(
            Update,
            (
                control_ball,
                process_events,
                sync_resource_to_ui::<InsideArea>.run_if(resource_changed::<InsideArea>),
            ),
        )
        .run();
}

/// Which area the sphere is in/touching
#[derive(Component, Debug, Clone)]
enum AreaMarker {
    Green,
    Blue,
}

/// Setup a basic scene with:
/// * Floor
/// * A light for dramatic shadows
/// * A sphere that can move
/// * Two cubes that designate area intersection
fn setup_physics_scene(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    // Create the ground.
    // Make this a physical looking object
    commands.spawn((
        Collider::cuboid(100.0, 0.1, 100.0),
        Transform::from_xyz(0.0, -1.0, 0.0),
        Mesh3d(meshes.add(Plane3d::new(Vec3::Y, Vec2::splat(50.0)))),
        MeshMaterial3d(materials.add(StandardMaterial {
            base_color: RED.into(),
            ..Default::default()
        })),
    ));

    commands.spawn((
        SpotLight {
            color: WHITE.into(),
            intensity: 10_000_000.0,
            shadows_enabled: true,
            ..default()
        },
        Transform::from_xyz(0.0, 10.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));

    // Create the bouncing ball.
    commands.spawn((
        RigidBody::Dynamic,
        GravityScale(1.0),
        Collider::ball(0.5),
        ColliderMassProperties::Mass(2.0),
        Restitution::coefficient(0.7),
        ExternalImpulse::default(),
        Transform::from_xyz(0.0, 4.0, 0.0),
        ActiveEvents::all(),
        Mesh3d(meshes.add(SphereMeshBuilder::new(
            0.5,
            SphereKind::Uv {
                sectors: 10,
                stacks: 10,
            },
        ))),
        MeshMaterial3d(materials.add(StandardMaterial {
            base_color: WHITE.into(),
            ..Default::default()
        })),
    ));

    // Create a box that the ball can pass into/through
    commands.spawn((
        Sensor,
        Collider::cuboid(1.0, 1.0, 1.0),
        Transform::from_xyz(0.0, 0.0, 2.0),
        Mesh3d(meshes.add(Cuboid::new(2.0, 2.0, 2.0))),
        MeshMaterial3d(materials.add(StandardMaterial {
            base_color: GREEN.with_alpha(0.5).into(),
            alpha_mode: AlphaMode::Blend,
            ..Default::default()
        })),
        AreaMarker::Green,
    ));

    // Create a box that the ball can pass into/through
    commands.spawn((
        Sensor,
        Collider::cuboid(1.0, 1.0, 1.0),
        Transform::from_xyz(0.0, 0.0, -2.0),
        Mesh3d(meshes.add(Cuboid::new(2.0, 2.0, 2.0))),
        MeshMaterial3d(materials.add(StandardMaterial {
            base_color: BLUE.with_alpha(0.5).into(),
            alpha_mode: AlphaMode::Blend,
            ..Default::default()
        })),
        AreaMarker::Blue,
    ));
}

/// Setup the UI for this example that indicates if the game "sees" the sphere
/// is inside the cube
fn setup_ui(mut commands: Commands) {
    commands.spawn((
        Node {
            align_self: AlignSelf::Start,
            justify_self: JustifySelf::Center,
            ..default()
        },
        Text("Placeholder".into()),
        SyncResource::<InsideArea>::default(),
    ));
}

/// Position the world camera to get a better view
fn position_camera(mut query: Query<&mut Transform, (With<Camera>, With<Camera3d>)>) {
    query.iter_mut().for_each(|mut t| {
        *t = Transform::from_xyz(10.0, 10.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y);
    })
}

/// Control the ball based on arrow keys
fn control_ball(keys: Res<ButtonInput<KeyCode>>, mut ball: Single<&mut ExternalImpulse>) {
    if keys.pressed(KeyCode::ArrowUp) {
        ball.torque_impulse = Vec3::new(0.0, 0.0, 0.1);
    }

    if keys.pressed(KeyCode::ArrowDown) {
        ball.torque_impulse = Vec3::new(0.0, 0.0, -0.1);
    }

    if keys.pressed(KeyCode::ArrowLeft) {
        ball.torque_impulse = Vec3::new(0.1, 0.0, 0.0);
    }

    if keys.pressed(KeyCode::ArrowRight) {
        ball.torque_impulse = Vec3::new(-0.1, 0.0, 0.0);
    }
}

/// Maps CollisionEvent to a game-specific construct (did X enter/exit an area)
#[derive(Debug)]
enum WithinBounds {
    Enter(Entity, Entity),
    Exit(Entity, Entity),
}

/// Resource tracking what box the sphere is in
#[derive(Resource, Debug, Default, Clone)]
struct InsideArea(Option<AreaMarker>);

impl Display for InsideArea {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self.0 {
            Some(AreaMarker::Blue) => write!(f, "Ball IS touching the BLUE box"),
            Some(AreaMarker::Green) => write!(f, "Ball IS touching the GREEN box"),
            None => write!(f, "Ball is NOT touching ANY box"),
        }
    }
}

/// Read collision events and procss them into resource updates to be displayed to the user
fn process_events(
    mut events: EventReader<CollisionEvent>,
    areas: Query<&AreaMarker>,
    mut inside: ResMut<InsideArea>,
) {
    events
        .read()
        .filter_map(|collision_event| match collision_event {
            CollisionEvent::Started(a, b, flags) => {
                (*flags == CollisionEventFlags::SENSOR).then_some(WithinBounds::Enter(*a, *b))
            }
            CollisionEvent::Stopped(a, b, flags) => {
                (*flags == CollisionEventFlags::SENSOR).then_some(WithinBounds::Exit(*a, *b))
            }
        })
        .for_each(|within_bounds| {
            match within_bounds {
                WithinBounds::Enter(a, b) => {
                    if let Ok(x) = areas.get(a) {
                        inside.0 = Some(x.clone());
                    } else if let Ok(x) = areas.get(b) {
                        inside.0 = Some(x.clone());
                    }
                }
                WithinBounds::Exit(a, b) => {
                    if areas.contains(a) || areas.contains(b) {
                        inside.0 = None;
                    }
                }
            }
        })
}