auto aim

src/aim.rs

@@ -0,0 +1,131 @@
+use crate::{
+    billboards::Billboard,
+    player::{Player, PlayerHead},
+    tb_entities::EnemySpawn,
+};
+use bevy::prelude::*;
+use bevy_sprite3d::{Sprite3dBuilder, Sprite3dParams};
+use std::f32::consts::PI;
+
+#[derive(Resource, Reflect)]
+#[reflect(Resource)]
+struct AimState {
+    pub target: Option<Entity>,
+    pub range: f32,
+    pub angle: f32,
+}
+
+impl Default for AimState {
+    fn default() -> Self {
+        Self {
+            target: None,
+            range: 40.,
+            angle: PI / 10.,
+        }
+    }
+}
+
+#[derive(Component, Reflect)]
+#[reflect(Component)]
+struct Marker;
+
+#[derive(Event)]
+enum MarkerEvent {
+    Spawn(Entity),
+    Despawn,
+}
+
+pub fn plugin(app: &mut App) {
+    app.init_resource::<AimState>();
+    app.add_systems(Update, update);
+    app.add_observer(marker_event);
+}
+
+fn marker_event(
+    trigger: Trigger<MarkerEvent>,
+    mut commands: Commands,
+    asset_server: Res<AssetServer>,
+    mut sprite_params: Sprite3dParams,
+    marker: Query<Entity, With<Marker>>,
+) {
+    for m in marker.iter() {
+        commands.entity(m).despawn_recursive();
+    }
+
+    let MarkerEvent::Spawn(target) = trigger.event() else {
+        return;
+    };
+
+    let selector = asset_server.load("ui/selector.png");
+
+    let id = commands
+        .spawn((
+            Name::new("aim-marker"),
+            Billboard,
+            Marker,
+            Transform::from_translation(Vec3::new(0., 3., 0.)),
+            Sprite3dBuilder {
+                image: selector,
+                pixels_per_metre: 30.,
+                alpha_mode: AlphaMode::Blend,
+                unlit: true,
+                ..default()
+            }
+            .bundle(&mut sprite_params),
+        ))
+        .id();
+
+    commands.entity(*target).add_child(id);
+}
+
+fn update(
+    mut commands: Commands,
+    mut state: ResMut<AimState>,
+    query: Query<(Entity, &Transform), With<EnemySpawn>>,
+    player_pos: Query<&Transform, With<Player>>,
+    player_rot: Query<&Transform, With<PlayerHead>>,
+) {
+    let Some(player_pos) = player_pos.iter().next().map(|t| t.translation) else {
+        return;
+    };
+
+    let Some(player_forward) = player_rot.iter().next().map(|t| t.forward()) else {
+        return;
+    };
+
+    let mut new_target = None;
+    let mut target_distance = f32::MAX;
+
+    for (e, t) in query.iter() {
+        let delta = player_pos - t.translation;
+
+        let distance = delta.length();
+
+        if distance > state.range {
+            continue;
+        }
+
+        let angle = player_forward.angle_between(delta.normalize());
+
+        if angle < state.angle && distance < target_distance {
+            new_target = Some(e);
+            target_distance = distance;
+        }
+    }
+
+    if let Some(e) = state.target {
+        if commands.get_entity(e).is_none() {
+            state.target = None;
+            return;
+        }
+    }
+
+    if new_target != state.target {
+        if let Some(target) = new_target {
+            commands.trigger(MarkerEvent::Spawn(target));
+        } else {
+            commands.trigger(MarkerEvent::Despawn);
+        }
+        state.target = new_target;
+    }
+}