Phunny Fysics

game/dist/project-constants.json

@@ -16,5 +16,10 @@
             "details.sm_failure": "Game went FUBAR",
             "details.main_menu": "In the main menu"
         }
+    },
+    "player": {
+        "max_velocity": 3,
+        "acceleration": 2,
+        "deceleration": 1
     }
 }

game/game_logic/src/project_constants.rs

@@ -28,6 +28,20 @@ pub struct DiscordConstants {
     pub strings: HashMap<String, String>,
 }
 
+/// Constants relating to the Player
+#[derive(Debug, Deserialize)]
+pub struct PlayerConstants {
+
+    /// Maximum velocity, tiles per second
+    pub max_velocity: u32,
+
+    /// Acceleration, tiles per second per second
+    pub acceleration: u32,
+
+    /// Deceleration, tiles per second per second
+    pub deceleration: u32,
+}
+
 /// This structure is filled with the contents of `dist/project-constants.json` at runtime
 #[derive(Debug, Deserialize)]
 pub struct ProjectConstants {
@@ -40,6 +54,9 @@ pub struct ProjectConstants {
     /// The Discord constants
     pub discord: DiscordConstants,
 
+    /// The Player constants
+    pub player: PlayerConstants,
+
     /// The target framerate of the game
     pub target_fps: u32,
 

game/game_logic/src/scenes/mod.rs

@@ -69,7 +69,7 @@ impl SceneRenderDelegate {
                     .render_frame(raylib, rl_thread, &discord, global_resources, constants)
                     .await;
                 self.scene_playable
-                    .update_physics(raylib)
+                    .update_physics(raylib, constants)
                     .await;
             }
             MenuStateSignal::QuitGame => unimplemented!(),

game/game_logic/src/scenes/player_interaction.rs

@@ -102,24 +102,45 @@ impl PlayableScene {
     pub async fn update_physics(
         &mut self,
         raylib: & raylib::RaylibHandle,
+        constants: &ProjectConstants,
     ) {
+
+        // Get time since last physics update
         let time = SystemTime::now();
-        if time
-            .duration_since(self.last_update)
-            .expect("Time Appears to Have Moved Backwards!")
-            .as_millis() < 16 
-        {
-            return
-        }
-            
+        let elapsed = time.duration_since(self.last_update).expect("Time Appears to Have Moved Backwards!");
         self.last_update = time;
+        let delta_time = elapsed.as_millis() as f32 / 1000.0; // Physics will be scaled by this value
 
         let player = &mut self.player;
+
+        // Get input direction components
         let h_axis = raylib.is_key_down(KeyboardKey::KEY_D) as i8 - raylib.is_key_down(KeyboardKey::KEY_A) as i8;
         let v_axis = raylib.is_key_down(KeyboardKey::KEY_W) as i8 - raylib.is_key_down(KeyboardKey::KEY_S) as i8;
-        let direction = na::Vector2::new(h_axis as f32, v_axis as f32);
-        player.velocity += &direction;
-        player.position += &player.velocity;
+        if h_axis != 0 || v_axis != 0 {
+            // Normalize input and accelerate in desired direction
+            let direction = na::Vector2::new(h_axis as f32, v_axis as f32).normalize();
+            player.velocity += &direction.xy() 
+                * constants.player.acceleration as f32
+                * constants.tile_size as f32 
+                * delta_time;
+        }
+
+        if player.velocity.magnitude() != 0.0 {
+            player.velocity -= player.velocity.normalize() 
+                * constants.player.deceleration as f32 
+                * constants.tile_size as f32 
+                * delta_time;
+            if player.velocity.magnitude() < 0.01 {
+                player.velocity.set_magnitude(0.0);
+            }
+        }
+
+        if ((constants.player.max_velocity * constants.tile_size) as f32) 
+            < player.velocity.magnitude() {
+            player.velocity.set_magnitude((constants.player.max_velocity * constants.tile_size) as f32);
+        }
+
+        player.position += &player.velocity * delta_time;
     }
 }