density repulsion

src/density_grid.rs

@@ -0,0 +1,80 @@
+use crate::globals::MAX_MAP_WIDTH;
+use crate::physics_body::PhysicsBody;
+use bevy::prelude::*;
+
+const CELL_SIZE: usize = 32;
+const MAX_MAP_SIZE: usize = MAX_MAP_WIDTH * 2;
+const ARRAY_WIDTH: usize = MAX_MAP_SIZE / CELL_SIZE;
+const GRID_ARRAY_SIZE: usize = ARRAY_WIDTH * ARRAY_WIDTH;
+
+const DENSITY_FORCE_SCALE: f32 = 100.0;
+
+#[derive(Resource)]
+pub struct DensityGrid {
+    grid: Box<[i32; GRID_ARRAY_SIZE]>,
+}
+
+impl DensityGrid {
+    pub fn new() -> Self {
+        DensityGrid { grid: Box::new([0; GRID_ARRAY_SIZE]) }
+    }
+}
+
+pub fn pos_to_grid_cell(pos: Vec2) -> UVec2 {
+    let ix = ((pos.x + MAX_MAP_WIDTH as f32) / CELL_SIZE as f32) as u32;
+    let iy = ((pos.y + MAX_MAP_WIDTH as f32) / CELL_SIZE as f32) as u32;
+    UVec2::new(ix, iy)
+}
+
+fn get_index_from_uvec2(grid_cell: UVec2) -> usize {
+    if grid_cell.x >= ARRAY_WIDTH as u32 || grid_cell.y >= ARRAY_WIDTH as u32 {
+        panic!("Index out of bounds: {:?}", grid_cell);
+    }
+    (grid_cell.x + grid_cell.y * ARRAY_WIDTH as u32) as usize
+}
+
+#[derive(Component, Default)]
+pub struct DensityObject {}
+
+pub fn init_density_object(mut density_grid: ResMut<DensityGrid>, mut query: Query<&Transform>) {
+    for transform in &mut query {
+        let grid_cell = pos_to_grid_cell(transform.translation.xy());
+        // println!("grid cell {:?}", grid_cell);
+        let index = get_index_from_uvec2(grid_cell);
+        density_grid.grid[index] += 1;
+    }
+}
+
+pub fn density_grid_update(mut density_grid: ResMut<DensityGrid>, query: Query<&Transform>) {
+    density_grid.grid.fill(0);
+
+    for transform in &query {
+        let cell = pos_to_grid_cell(transform.translation.xy());
+        let idx = get_index_from_uvec2(cell);
+        density_grid.grid[idx] += 1;
+    }
+}
+
+pub fn density_grid_force(
+    density_grid: Res<DensityGrid>,
+    mut query: Query<(&mut PhysicsBody, &Transform), With<DensityObject>>,
+) {
+    for (mut physics_body, transform) in &mut query {
+        let grid_cell = pos_to_grid_cell(transform.translation.xy());
+        let mut density_gradient = Vec2::ZERO;
+
+        for dx in [-1, 0, 1] {
+            for dy in [-1, 0, 1] {
+                let offset = IVec2 { x: dx, y: dy };
+                let neighbor_cell = (offset + grid_cell.as_ivec2()).as_uvec2();
+                let index = get_index_from_uvec2(neighbor_cell);
+                let density = density_grid.grid[index];
+
+                // println!("offset : {:?} density: {:?}", offset.as_vec2(), density);
+                density_gradient += offset.as_vec2() * density as f32;
+            }
+        }
+        // println!("density : {:?}", density_gradient);
+        physics_body.force -= density_gradient * DENSITY_FORCE_SCALE;
+    }
+}

src/globals.rs

@@ -0,0 +1 @@
+pub static MAX_MAP_WIDTH: usize = 1024;

src/kirby.rs

@@ -10,14 +10,9 @@ pub struct Kirby {
 
 pub fn kirby_spawn(mut commands: Commands, asset_server: Res<AssetServer>) {
     let sprite = Sprite::from_image(asset_server.load("sprites/kirby.png"));
-    let body = PhysicsBody {
-        mass: 10.0,
-        force: Vec2::ZERO,
-        velocity: Vec2::ZERO,
-        drag: 0.05,
-    };
+    let body = PhysicsBody { mass: 10.0, force: Vec2::ZERO, velocity: Vec2::ZERO, drag: 0.05 };
     let transform = Transform::from_xyz(0.0, 0.0, 0.0).with_scale(Vec3::ONE * 0.25);
-    commands.spawn((Kirby { speed_force: 50.0 }, transform, sprite, body));
+    commands.spawn((Kirby { speed_force: 10000.0 }, transform, sprite, body));
 }
 
 pub fn get_dir(keys: Res<ButtonInput<KeyCode>>) -> Vec2 {
@@ -43,16 +38,13 @@ pub fn get_dir(keys: Res<ButtonInput<KeyCode>>) -> Vec2 {
     dir.normalize_or_zero()
 }
 
-pub fn kirby_player_move(
-    keys: Res<ButtonInput<KeyCode>>,
-    mut query: Query<(&mut PhysicsBody, &Kirby), With<Kirby>>,
-) {
+pub fn kirby_player_move(keys: Res<ButtonInput<KeyCode>>, mut query: Query<(&mut PhysicsBody, &Kirby), With<Kirby>>) {
     if keys.pressed(KeyCode::Space) {
         println!("SUCKING");
     }
     let dir = get_dir(keys);
     for (mut body, kirby) in &mut query {
-        body.velocity += dir * kirby.speed_force;
+        body.force += dir * kirby.speed_force;
     }
 }
 

src/lana.rs

@@ -0,0 +1,57 @@
+use crate::density_grid::DensityObject;
+use crate::kirby::Kirby;
+use crate::physics_body::PhysicsBody;
+use crate::sphere_collider::SphereCollider;
+use bevy::prelude::*;
+use rand::Rng;
+use std::f32::consts::TAU;
+
+#[derive(Component)]
+#[require(Sprite, PhysicsBody, SphereCollider, DensityObject)]
+pub struct Lana {
+    move_force: f32,
+}
+
+pub fn lana_spawn(mut commands: Commands, asset_server: Res<AssetServer>) {
+    let texture: Handle<Image> = asset_server.load("sprites/lana.png");
+    let mut rng = rand::rng();
+
+    for _ in 0..1_000 {
+        let angle = rng.random_range(0.0..TAU);
+        let pos = Vec2::from_angle(angle) * 500.0;
+
+        commands.spawn((
+            Lana { move_force: 3000.0 },
+            Sprite { image: texture.clone(), ..default() },
+            Transform::from_translation(pos.extend(0.0)).with_scale(Vec3::splat(0.02)),
+            PhysicsBody { mass: 10.0, force: Vec2::ZERO, velocity: Vec2::ZERO, drag: 0.05 },
+        ));
+    }
+}
+
+pub fn lana_move(
+    mut lana_query: Query<(&mut PhysicsBody, &Transform, &Lana), With<Lana>>,
+    kirby_query: Query<(&Transform, &Kirby), With<Kirby>>,
+) {
+    for (mut lana_body, lana_transform, lana) in &mut lana_query {
+        let mut nearest_kirby_pos = Vec3::ZERO;
+        let mut nearest_squared = f32::MAX;
+
+        for (kirby_transform, _kirby) in kirby_query {
+            let dist_squared = kirby_transform.translation.distance_squared(lana_transform.translation);
+            if (dist_squared) < nearest_squared {
+                nearest_squared = dist_squared;
+                nearest_kirby_pos = kirby_transform.translation;
+            }
+        }
+
+        let dir = (nearest_kirby_pos - lana_transform.translation).normalize().xy();
+        lana_body.force += dir * lana.move_force;
+    }
+}
+
+#[derive(Component)]
+#[require(Sprite, Transform)]
+pub struct KirbySuction {
+    box_size: Vec2,
+}

src/main.rs

@@ -1,12 +1,21 @@
 use bevy::prelude::*;
 use camera::spawn_camera;
+use density_grid::DensityGrid;
+use density_grid::density_grid_force;
+use density_grid::density_grid_update;
+use density_grid::init_density_object;
 use kirby::kirby_player_move;
 use kirby::kirby_spawn;
+use lana::lana_move;
+use lana::lana_spawn;
 use map::MapBounds;
 use physics_body::integrate;
 
 mod camera;
+mod density_grid;
+mod globals;
 mod kirby;
+mod lana;
 mod map;
 mod physics_body;
 mod sphere_collider;
@@ -14,12 +23,15 @@ mod sphere_collider;
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
-        .insert_resource(MapBounds {
-            min: Vec2::ONE * -400.0,
-            max: Vec2::ONE * 400.0,
-        })
+        .insert_resource(MapBounds { min: Vec2::ONE * -600.0, max: Vec2::ONE * 600.0 })
+        .insert_resource(DensityGrid::new())
         .add_systems(Startup, spawn_camera)
         .add_systems(Startup, kirby_spawn)
-        .add_systems(FixedUpdate, (kirby_player_move, integrate).chain())
+        .add_systems(Startup, lana_spawn)
+        .add_systems(PostStartup, init_density_object)
+        .add_systems(FixedUpdate, (density_grid_update, density_grid_force).chain())
+        .add_systems(FixedUpdate, kirby_player_move)
+        .add_systems(FixedUpdate, lana_move)
+        .add_systems(FixedPostUpdate, integrate)
         .run();
 }

src/physics_body.rs

@@ -35,7 +35,7 @@ pub fn integrate(
         physicsbody.velocity += force * delta_secs / mass;
         physicsbody.velocity *= 1.0 - drag;
 
-        bounce(&mut physicsbody.velocity, &transform, &bounds);
+        map_bounce(&mut physicsbody.velocity, &transform, &bounds);
 
         transform.translation.x += physicsbody.velocity.x * delta_secs;
         transform.translation.y += physicsbody.velocity.y * delta_secs;
@@ -44,7 +44,7 @@ pub fn integrate(
     }
 }
 
-fn bounce(velocity: &mut Vec2, transform: &Transform, bounds: &MapBounds) {
+fn map_bounce(velocity: &mut Vec2, transform: &Transform, bounds: &MapBounds) {
     if (transform.translation.x < bounds.min.x && velocity.x < 0.0)
         || (transform.translation.x > bounds.max.x && velocity.x > 0.0)
     {

src/sphere_collider.rs

@@ -5,3 +5,13 @@ use bevy::{prelude::*, render::renderer};
 pub struct SphereCollider {
     pub radius: f32,
 }
+
+impl SphereCollider {
+    fn point_inside(&self, self_pos: Vec3, point: Vec3) -> bool {
+        (self_pos - point).length_squared() < self.radius * self.radius
+    }
+    fn collides(&self, self_pos: Vec3, other: &SphereCollider, other_pos: Vec3) -> bool {
+        let radius_sum = self.radius + other.radius;
+        (self_pos - other_pos).length_squared() < radius_sum * radius_sum
+    }
+}