based off the bevy gizmos example

.gitignore

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+/target

Cargo.toml

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+[package]
+name = "audubon"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+argh = "0.1.12"
+bevy = "0.12.0"
+rand = "0.8.5"
+rstar = "0.11.0"

LICENSE.md

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+# The Chaos License (GLP)
+
+This software is released under the terms of the Chaos License. In cases where the terms of the
+license are unclear, refer to the [Fuck Around and Find Out
+License](https://git.sr.ht/~boringcactus/fafol/tree/master/LICENSE-v0.2.md).

src/lib.rs

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+use argh::FromArgs;
+use bevy::prelude::*;
+
+#[derive(Debug, FromArgs, Resource)]
+/// Toid Watching
+pub struct Config {
+    /// how many Toids to spawn
+    #[argh(option, short = 't', default = "100")]
+    pub toids: usize,
+}
+
+pub type Point = (f32, f32, f32);
+
+pub type Toint = rstar::primitives::GeomWithData<Point, Entity>;
+
+pub trait Pointable {
+    fn to_point(&self) -> Point;
+}
+
+impl Pointable for Vec3 {
+    fn to_point(&self) -> Point {
+        (self.x, self.y, self.z)
+    }
+}
+
+#[derive(Resource, Deref, DerefMut)]
+pub struct Index(pub rstar::RTree<Toint>);
+
+#[derive(Component, Debug, Clone, Deref, DerefMut, Default)]
+pub struct Buddies(Vec<Entity>);
+
+#[derive(Component, Debug, Clone, Deref, DerefMut, Default)]
+pub struct Velocity(Vec3);
+
+#[derive(Component)]
+pub struct Toid;
+
+pub fn turkey_time(commands: &mut Commands, scene: &Handle<Scene>) -> Entity {
+    commands
+        .spawn(SpatialBundle::default())
+        .insert((Velocity::default(), Buddies::default(), Toid))
+        .with_children(|t| {
+            t.spawn(SceneBundle {
+                scene: scene.to_owned(),
+                ..Default::default()
+            })
+            .insert(Transform::from_rotation(Quat::from_axis_angle(
+                Vec3::Y,
+                -std::f32::consts::FRAC_PI_2,
+            )));
+        })
+        .id()
+}
+
+pub fn add_gizmos(mut gizmos: Gizmos, toids: Query<(&Transform, Entity), With<Toid>>) {
+    let gizmos = &mut gizmos;
+    for (pos, _entity) in toids.iter() {
+        let nudge = pos.up() * 0.15;
+        let rpos = pos.translation + nudge;
+        gizmos.ray(rpos, pos.forward(), Color::RED);
+    }
+}

src/main.rs

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+//use std::f32::consts::PI;
+
+use bevy::prelude::*;
+
+use audubon::*;
+
+fn main() {
+    let config: audubon::Config = argh::from_env();
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .insert_resource(config)
+        .add_systems(Startup, setup)
+        .add_systems(
+            Update,
+            (
+                add_gizmos,
+                rotate_camera,
+                update_config,
+                bevy::window::close_on_esc,
+            ),
+        )
+        .run();
+}
+
+fn setup(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+    config: Res<Config>,
+    models: Res<AssetServer>,
+) {
+    commands.spawn(Camera3dBundle {
+        transform: Transform::from_xyz(0., 1.5, 6.).looking_at(Vec3::ZERO, Vec3::Y),
+        ..default()
+    });
+    // plane
+    commands.spawn(PbrBundle {
+        mesh: meshes.add(Mesh::from(shape::Plane::from_size(5.0))),
+        material: materials.add(Color::rgb(0.3, 0.5, 0.3).into()),
+        ..default()
+    });
+
+    let toid_model = models.load("models/boid.glb#Scene0");
+
+    for _ in 0..config.toids {
+        let _ = turkey_time(&mut commands, &toid_model);
+    }
+
+    // light
+    commands.spawn(PointLightBundle {
+        point_light: PointLight {
+            intensity: 1500.0,
+            shadows_enabled: true,
+            ..default()
+        },
+        transform: Transform::from_xyz(4.0, 8.0, 4.0),
+        ..default()
+    });
+
+    // example instructions
+    commands.spawn(
+        TextBundle::from_section(
+            "Press 'D' to toggle drawing gizmos on top of everything else in the scene\n\
+            Press 'P' to toggle perspective for line gizmos\n\
+            Hold 'Left' or 'Right' to change the line width",
+            TextStyle {
+                font_size: 20.,
+                ..default()
+            },
+        )
+        .with_style(Style {
+            position_type: PositionType::Absolute,
+            top: Val::Px(12.0),
+            left: Val::Px(12.0),
+            ..default()
+        }),
+    );
+}
+
+fn rotate_camera(mut query: Query<&mut Transform, With<Camera>>, time: Res<Time>) {
+    let mut transform = query.single_mut();
+
+    transform.rotate_around(Vec3::ZERO, Quat::from_rotation_y(time.delta_seconds() / 2.));
+}
+
+fn update_config(mut config: ResMut<GizmoConfig>, keyboard: Res<Input<KeyCode>>, time: Res<Time>) {
+    if keyboard.just_pressed(KeyCode::D) {
+        config.depth_bias = if config.depth_bias == 0. { -1. } else { 0. };
+    }
+    if keyboard.just_pressed(KeyCode::P) {
+        // Toggle line_perspective
+        config.line_perspective ^= true;
+        // Increase the line width when line_perspective is on
+        config.line_width *= if config.line_perspective { 5. } else { 1. / 5. };
+    }
+
+    if keyboard.pressed(KeyCode::Right) {
+        config.line_width += 5. * time.delta_seconds();
+    }
+    if keyboard.pressed(KeyCode::Left) {
+        config.line_width -= 5. * time.delta_seconds();
+    }
+}