Physics refactored out

src/main.rs

@@ -4,7 +4,9 @@ mod player;
 
 use bevy::{image::Image, math::I64Vec2, prelude::*};
 
-use crate::player::Player;
+use crate::{physics::PhysicsBody2D, player::Player};
+
+const UNITS_TO_PX_SCALE: i64 = 256;
 
 #[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Hash, States)]
 enum AppState {
@@ -151,10 +153,8 @@ fn levelload(
             ));
             match ei.identifier.as_str() {
                 "Player" => {
-                    spawned_ent.insert(Player {
-                        pos,
-                        vel: I64Vec2::ZERO,
-                    });
+                    spawned_ent.insert(Player {});
+                    spawned_ent.insert(PhysicsBody2D { pos, ..default() });
                     spawned_ent.insert(Sprite::from_color(Color::WHITE, vec2(16., 16.)));
                 }
                 "Parsnip" => {
@@ -173,10 +173,8 @@ fn levelload(
 
 fn gameloop(
     keyb: Res<ButtonInput<KeyCode>>,
-    mut player_sing: Single<(&mut Player, &mut Transform)>,
+    mut player_sing: Single<(&mut PhysicsBody2D, &mut Transform), With<Player>>,
 ) {
-    const UNITS_TO_PX_SCALE: i64 = 100;
-    const MAX_SPEED: i64 = 2 * UNITS_TO_PX_SCALE;
     let mut dir = I64Vec2::ZERO;
 
     if keyb.pressed(KeyCode::KeyA) || keyb.pressed(KeyCode::ArrowLeft) {
@@ -195,51 +193,22 @@ fn gameloop(
         dir.y = -1;
     }
 
-    let player = player_sing.0.as_mut();
+    let play_phys = player_sing.0.as_mut();
 
-    // player vel and pos are in px / 100
-    let mut p_vel = player.vel + dir * UNITS_TO_PX_SCALE * MAX_SPEED;
+    // player vel and pos are in UNITS_TO_PX_SCALE
     if dir.length_squared() == 0 {
-        p_vel = (p_vel * 8) / 10;
-        info!("Slowing! {p_vel}");
+        // very bare bones player friction
+        play_phys.vel *= 6;
+        play_phys.vel /= 10;
     } else {
-        info!("Changing vel: {p_vel}")
+        play_phys.add_vel(dir * UNITS_TO_PX_SCALE);
     }
 
-    // want unit vector with int math
-    // normally this would be x / len, y / len
-
-    // eg (2,2) -> length of 4 -> (0.5, 0.5)
-    // how to do with squares?
-
-    // (2, 2) -> sqr length of 8 -> sqr x / 8 -> 0.5... yes?
-    // but we can't get half units obvs so we need to work in centi-units
-    // 200, 200 -> should become 50, 50
-
-    // max speed is 3 px per update
-    if p_vel.length_squared() >= MAX_SPEED.pow(2) {
-        let l = p_vel.length_squared();
-        let x = p_vel.x * p_vel.x;
-        let y = p_vel.y * p_vel.y;
-
-        p_vel.x = match p_vel.x {
-            ..0 => (x * -MAX_SPEED) / l,
-            _ => (x * MAX_SPEED) / l,
-        };
-        p_vel.y = match p_vel.y {
-            ..0 => (y * -MAX_SPEED) / l,
-            _ => (y * MAX_SPEED) / l,
-        };
-
-        info!("Nerfed speed {p_vel}");
-    }
-
-    player.vel = p_vel;
-    player.pos += p_vel;
+    play_phys.tick();
 
     *player_sing.1 = Transform::from_xyz(
-        (player.pos.x as f32) / UNITS_TO_PX_SCALE as f32,
-        (player.pos.y as f32) / UNITS_TO_PX_SCALE as f32,
+        (play_phys.pos.x as f32) / UNITS_TO_PX_SCALE as f32,
+        (play_phys.pos.y as f32) / UNITS_TO_PX_SCALE as f32,
         100.,
     );
 }

src/physics.rs

@@ -0,0 +1,34 @@
+use bevy::{ecs::component::Component, math::I64Vec2};
+
+const MAX_SPEED: i64 = 256;
+
+#[derive(Default, Debug, Component)]
+pub struct PhysicsBody2D {
+    pub pos: I64Vec2,
+    pub vel: I64Vec2,
+}
+
+impl PhysicsBody2D {
+    pub fn tick(&mut self) {
+        self.pos += self.vel;
+    }
+
+    pub fn add_vel(&mut self, force: I64Vec2) {
+        let mut vel = self.vel + force;
+        if vel.length_squared() >= MAX_SPEED.pow(2) {
+            let l = vel.length_squared();
+            let x = vel.x * vel.x;
+            let y = vel.y * vel.y;
+
+            vel.x = match vel.x {
+                ..0 => (x * -MAX_SPEED) / l,
+                _ => (x * MAX_SPEED) / l,
+            };
+            vel.y = match vel.y {
+                ..0 => (y * -MAX_SPEED) / l,
+                _ => (y * MAX_SPEED) / l,
+            };
+        }
+        self.vel = vel;
+    }
+}

src/player.rs

@@ -1,10 +1,4 @@
-use bevy::{
-    ecs::component::Component,
-    math::{I64Vec2, IVec2},
-};
+use bevy::ecs::component::Component;
 
 #[derive(Default, Debug, Component)]
-pub struct Player {
-    pub pos: I64Vec2,
-    pub vel: I64Vec2,
-}
+pub struct Player {}