movement affected by walking in water

src/control/controller.rs

@@ -50,6 +50,10 @@ pub struct PlayerMovement {
 #[reflect(Component)]
 pub struct MovementAcceleration(Scalar);
 
+#[derive(Component, Reflect)]
+#[reflect(Component)]
+pub struct MovementSpeedFactor(pub f32);
+
 /// The strength of a jump.
 #[derive(Component, Reflect)]
 #[reflect(Component)]
@@ -85,6 +89,7 @@ pub struct MovementBundle {
     acceleration: MovementAcceleration,
     jump_impulse: JumpImpulse,
     max_slope_angle: MaxSlopeAngle,
+    factor: MovementSpeedFactor,
 }
 
 impl MovementBundle {
@@ -93,6 +98,7 @@ impl MovementBundle {
             acceleration: MovementAcceleration(acceleration),
             jump_impulse: JumpImpulse(jump_impulse),
             max_slope_angle: MaxSlopeAngle(max_slope_angle),
+            factor: MovementSpeedFactor(1.),
         }
     }
 }
@@ -173,6 +179,7 @@ fn movement(
     controls: Res<Controls>,
     mut controllers: Query<(
         &MovementAcceleration,
+        &MovementSpeedFactor,
         &JumpImpulse,
         &mut LinearVelocity,
         Has<Grounded>,
@@ -194,7 +201,8 @@ fn movement(
 
     direction = direction.normalize_or_zero();
 
-    for (movement_acceleration, jump_impulse, mut linear_velocity, is_grounded) in &mut controllers
+    for (movement_acceleration, factor, jump_impulse, mut linear_velocity, is_grounded) in
+        &mut controllers
     {
         let mut direction = direction.extend(0.0).xzy();
 
@@ -203,8 +211,8 @@ fn movement(
                 (rig_transform.forward() * direction.z) + (rig_transform.right() * direction.x);
         }
 
-        linear_velocity.x = -direction.x * movement_acceleration.0 * delta_time;
-        linear_velocity.z = -direction.z * movement_acceleration.0 * delta_time;
+        linear_velocity.x = -direction.x * movement_acceleration.0 * delta_time * factor.0;
+        linear_velocity.z = -direction.z * movement_acceleration.0 * delta_time * factor.0;
 
         if is_grounded && jump_requested && !*jump_used {
             linear_velocity.y = jump_impulse.0;

src/main.rs

@@ -23,6 +23,7 @@ mod player;
 mod sounds;
 mod tb_entities;
 mod utils;
+mod water;
 
 use avian3d::prelude::*;
 use bevy::{
@@ -146,6 +147,7 @@ fn main() {
     app.add_plugins(cash_heal::plugin);
     app.add_plugins(debug::plugin);
     app.add_plugins(utils::observers::plugin);
+    app.add_plugins(water::plugin);
 
     app.init_state::<GameState>();
 

src/water.rs

@@ -0,0 +1,93 @@
+use crate::{
+    GameState, control::controller::MovementSpeedFactor, global_observer, player::Player,
+    tb_entities::Water,
+};
+use avian3d::prelude::*;
+use bevy::prelude::*;
+
+#[derive(Component, Reflect)]
+#[reflect(Component)]
+struct WaterSensor;
+
+#[derive(Event)]
+struct PlayerInWater {
+    player: Entity,
+    entered: bool,
+}
+
+pub fn plugin(app: &mut App) {
+    app.add_systems(OnEnter(GameState::Playing), setup);
+    app.add_systems(
+        Update,
+        check_water_collision.run_if(in_state(GameState::Playing)),
+    );
+    global_observer!(app, on_player_water);
+}
+
+fn setup(mut commands: Commands, query: Query<(Entity, &Children), With<Water>>) {
+    for (e, c) in query.iter() {
+        assert!(c.len() == 1);
+        let child = c.iter().next().unwrap();
+
+        commands.entity(e).insert((
+            Sensor,
+            ColliderConstructorHierarchy::new(ColliderConstructor::TrimeshFromMesh),
+        ));
+
+        commands.entity(*child).insert(WaterSensor);
+    }
+}
+
+fn check_water_collision(
+    mut cmds: Commands,
+    mut collisionstart_events: EventReader<CollisionStarted>,
+    mut collisionend_events: EventReader<CollisionEnded>,
+    query_player: Query<&Player>,
+    query_water: Query<(Entity, &WaterSensor)>,
+) {
+    let start_events = collisionstart_events
+        .read()
+        .map(|CollisionStarted(e1, e2)| (true, *e1, *e2));
+    let end_events = collisionend_events
+        .read()
+        .map(|CollisionEnded(e1, e2)| (false, *e1, *e2));
+
+    for (started, e1, e2) in start_events.chain(end_events) {
+        let entities = [e1, e2];
+
+        let player = entities
+            .iter()
+            .find(|e| query_player.contains(**e))
+            .copied();
+        let water = entities.iter().find(|e| query_water.contains(**e)).copied();
+
+        if !(player.is_some() && water.is_some()) {
+            continue;
+        }
+
+        let Some(player) = player else {
+            continue;
+        };
+
+        cmds.trigger(PlayerInWater {
+            player,
+            entered: started,
+        });
+    }
+}
+
+fn on_player_water(
+    trigger: Trigger<PlayerInWater>,
+    //TODO: use a sparse set component `InWater` that we attach to the player
+    // then we can have a movement factor system that reacts on these components to update the factor
+    // PLUS we can then always adhoc check if a player is `InWater` to play an according sound and such
+    mut query: Query<&mut MovementSpeedFactor, With<Player>>,
+) {
+    let player = trigger.player;
+
+    let Ok(mut factor) = query.get_mut(player) else {
+        return;
+    };
+
+    factor.0 = if trigger.entered { 0.5 } else { 1. };
+}