refactor(ecs): another small speedup for archetypes

crates/comet_app/src/app.rs

@@ -1,5 +1,7 @@
 use comet_colors::{Color as ColorTrait, LinearRgba};
-use comet_ecs::{Camera2D, Component, Entity, Render2D, Scene, Text, Transform2D, Transform3D};
+use comet_ecs::{
+    Camera2D, Component, Entity, EntityId, Render2D, Scene, Text, Transform2D, Transform3D,
+};
 use comet_input::keyboard::Key;
 use comet_log::*;
 use comet_renderer::renderer::Renderer;
@@ -163,22 +165,22 @@ impl App {
     }
 
     /// Creates a new entity and returns its ID.
-    pub fn new_entity(&mut self) -> usize {
-        self.scene.new_entity() as usize
+    pub fn new_entity(&mut self) -> EntityId {
+        self.scene.new_entity()
     }
 
     /// Deletes an entity by its ID.
-    pub fn delete_entity(&mut self, entity_id: usize) {
+    pub fn delete_entity(&mut self, entity_id: EntityId) {
         self.scene.delete_entity(entity_id)
     }
 
     /// Gets an immutable reference to an entity by its ID.
-    pub fn get_entity(&self, entity_id: usize) -> Option<&Entity> {
+    pub fn get_entity(&self, entity_id: EntityId) -> Option<&Entity> {
         self.scene.get_entity(entity_id)
     }
 
     /// Gets a mutable reference to an entity by its ID.
-    pub fn get_entity_mut(&mut self, entity_id: usize) -> Option<&mut Entity> {
+    pub fn get_entity_mut(&mut self, entity_id: EntityId) -> Option<&mut Entity> {
         self.scene.get_entity_mut(entity_id)
     }
 
@@ -194,29 +196,29 @@ impl App {
 
     /// Adds a component to an entity by its ID and an instance of the component.
     /// Overwrites the previous component if another component of the same type is added.
-    pub fn add_component<C: Component>(&mut self, entity_id: usize, component: C) {
+    pub fn add_component<C: Component>(&mut self, entity_id: EntityId, component: C) {
         self.scene.add_component(entity_id, component)
     }
 
     /// Removes a component from an entity by its ID.
-    pub fn remove_component<C: Component>(&mut self, entity_id: usize) {
+    pub fn remove_component<C: Component>(&mut self, entity_id: EntityId) {
         self.scene.remove_component::<C>(entity_id)
     }
 
     /// Returns a reference to a component of an entity by its ID.
-    pub fn get_component<C: Component>(&self, entity_id: usize) -> Option<&C> {
+    pub fn get_component<C: Component>(&self, entity_id: EntityId) -> Option<&C> {
         self.scene.get_component::<C>(entity_id)
     }
 
     /// Returns a mutable reference to a component of an entity by its ID.
-    pub fn get_component_mut<C: Component>(&mut self, entity_id: usize) -> Option<&mut C> {
+    pub fn get_component_mut<C: Component>(&mut self, entity_id: EntityId) -> Option<&mut C> {
         self.scene.get_component_mut::<C>(entity_id)
     }
 
     /// Returns a list of entities that have the given components.
     /// The amount of queriable components is limited to 3 such that the `Archetype` creation is more efficient.
     /// Otherwise it would be a factorial complexity chaos.
-    pub fn get_entities_with(&self, components: Vec<TypeId>) -> Vec<usize> {
+    pub fn get_entities_with(&self, components: Vec<TypeId>) -> Vec<EntityId> {
         self.scene.get_entities_with(components)
     }
 
@@ -233,7 +235,7 @@ impl App {
     }
 
     /// Returns whether an entity has the given component.
-    pub fn has<C: Component>(&self, entity_id: usize) -> bool {
+    pub fn has<C: Component>(&self, entity_id: EntityId) -> bool {
         self.scene.has::<C>(entity_id)
     }
 
@@ -243,7 +245,7 @@ impl App {
     }
 
     /// Spawns a prefab with the given name.
-    pub fn spawn_prefab(&mut self, name: &str) -> Option<usize> {
+    pub fn spawn_prefab(&mut self, name: &str) -> Option<EntityId> {
         self.scene.spawn_prefab(name)
     }
 

crates/comet_ecs/component_derive/src/lib.rs

@@ -27,6 +27,13 @@ pub fn component_derive(input: TokenStream) -> TokenStream {
         }
     });
 
+    let clone_fields = fields.iter().map(|field| {
+        let field_name = &field.ident;
+        quote! {
+            #field_name: self.#field_name.clone()
+        }
+    });
+
     let default_fields = if let Data::Struct(data) = &input.data {
         match &data.fields {
             Fields::Named(fields) => fields
@@ -83,13 +90,11 @@ pub fn component_derive(input: TokenStream) -> TokenStream {
         impl Clone for #name {
             fn clone(&self) -> Self {
                 Self {
-                    ..*self
+                    #(#clone_fields),*
                 }
             }
         }
 
-        impl Copy for #name {}
-
         impl std::fmt::Debug for #name {
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 f.debug_struct(stringify!(#name))

crates/comet_ecs/src/archetypes.rs

@@ -1,9 +1,9 @@
 use comet_structs::ComponentSet;
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 
 #[derive(Debug, Clone)]
 pub struct Archetypes {
-    archetypes: HashMap<ComponentSet, HashSet<u32>>,
+    archetypes: HashMap<ComponentSet, Vec<u32>>,
 }
 
 impl Archetypes {
@@ -13,27 +13,31 @@ impl Archetypes {
         }
     }
 
-    pub fn component_sets(&self) -> Vec<ComponentSet> {
-        self.archetypes.keys().cloned().collect()
+    pub fn component_sets(&self) -> impl Iterator<Item = &ComponentSet> {
+        self.archetypes.keys()
     }
 
     pub fn create_archetype(&mut self, components: ComponentSet) {
-        self.archetypes.insert(components, HashSet::new());
+        self.archetypes.entry(components).or_insert_with(Vec::new);
     }
 
-    pub fn get_archetype(&self, components: &ComponentSet) -> Option<&HashSet<u32>> {
+    pub fn get_archetype(&self, components: &ComponentSet) -> Option<&Vec<u32>> {
         self.archetypes.get(components)
     }
 
     pub fn add_entity_to_archetype(&mut self, components: &ComponentSet, entity: u32) {
         if let Some(archetype) = self.archetypes.get_mut(components) {
-            archetype.insert(entity);
+            if !archetype.iter().any(|&e| e == entity) {
+                archetype.push(entity);
+            }
         }
     }
 
     pub fn remove_entity_from_archetype(&mut self, components: &ComponentSet, entity: u32) {
         if let Some(archetype) = self.archetypes.get_mut(components) {
-            archetype.retain(|&id| id != entity);
+            if let Some(pos) = archetype.iter().position(|&id| id == entity) {
+                archetype.swap_remove(pos);
+            }
         }
     }
 

crates/comet_ecs/src/component.rs

@@ -5,6 +5,7 @@
 // They are intended to work with the base suite of systems provided by the engine.
 use crate::math::{v2, v3};
 use crate::{Entity, Scene};
+use comet_log::*;
 use comet_colors::Color as ColorTrait;
 use comet_math::m4;
 use component_derive::Component;
@@ -110,10 +111,13 @@ pub struct Transform3D {
 // #                    TRAITS                      #
 // ##################################################
 
-pub trait Component: Send + Sync + PartialEq + Default + 'static {
+pub trait Component: Send + Sync + 'static {
     fn new() -> Self
     where
-        Self: Sized;
+        Self: Sized + Default,
+    {
+        Default::default()
+    }
 
     fn type_id() -> std::any::TypeId {
         std::any::TypeId::of::<Self>()
@@ -136,7 +140,7 @@ pub trait Render {
 }
 
 pub trait Camera {
-    fn get_visible_entities(&self, camera_position: Position2D, scene: Scene) -> Vec<Entity>;
+    fn get_visible_entities(&self, camera_position: &Position2D, scene: &Scene) -> Vec<Entity>;
     fn get_projection_matrix(&self) -> m4;
 }
 
@@ -246,8 +250,8 @@ impl Rectangle2D {
         }
     }
 
-    pub fn position(&self) -> Position2D {
-        self.position
+    pub fn position(&self) -> &Position2D {
+        &self.position
     }
 
     pub fn set_position(&mut self, position: Position2D) {
@@ -417,7 +421,7 @@ impl Camera2D {
         self.priority = priority;
     }
 
-    pub fn in_view_frustum(&self, camera_pos: Position2D, entity: Position2D) -> bool {
+    pub fn in_view_frustum(&self, camera_pos: &Position2D, entity: &Position2D) -> bool {
         let left = camera_pos.x() - self.zoom;
         let right = camera_pos.x() + self.zoom;
         let bottom = camera_pos.y() - self.zoom;
@@ -428,18 +432,19 @@ impl Camera2D {
 }
 
 impl Camera for Camera2D {
-    fn get_visible_entities(&self, camera_position: Position2D, scene: Scene) -> Vec<Entity> {
+    fn get_visible_entities(&self, camera_position: &Position2D, scene: &Scene) -> Vec<Entity> {
         let entities = scene.entities();
         let mut visible_entities = Vec::new();
         for entity in entities {
-            if self.in_view_frustum(
-                camera_position,
-                *scene
-                    .get_component::<Transform2D>(*entity.clone().unwrap().id() as usize)
-                    .unwrap()
-                    .position(),
-            ) {
-                visible_entities.push(entity.clone().unwrap());
+            if let Some(ent) = entity.clone() {
+                let id = ent.id();
+                if let Some(transform) = scene.get_component::<Transform2D>(id) {
+                    if self.in_view_frustum(camera_position, transform.position()) {
+                        visible_entities.push(ent);
+                    }
+                } else {
+                    error!("Entity {} missing Transform2D", id.index);
+                }
             }
         }
         visible_entities
@@ -498,7 +503,7 @@ impl Text {
     }
 
     pub fn color(&self) -> Color {
-        self.color
+        self.color.clone()
     }
 
     pub fn set_visibility(&mut self, visibility: bool) {

crates/comet_ecs/src/entity.rs

@@ -1,21 +1,35 @@
 use bit_set::BitSet;
 
+/// Handle used to reference entities safely. Contains an index into the entity
+/// storage and a generation counter to detect stale handles.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct EntityId {
+    pub index: u32,
+    pub gen: u32,
+}
+
+impl Default for EntityId {
+    fn default() -> Self {
+        Self { index: 0, gen: 0 }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub struct Entity {
-	id: u32,
-	components: BitSet
+    id: EntityId,
+    components: BitSet,
 }
 
 impl Entity {
-	pub(crate) fn new(id: u32) -> Self {
+    pub(crate) fn new(index: u32, gen: u32) -> Self {
         Self {
-			id,
-			components: BitSet::new()
+            id: EntityId { index, gen },
+            components: BitSet::new(),
         }
     }
 
-	pub fn id(&self) -> &u32 {
-		&self.id
+    pub fn id(&self) -> EntityId {
+        self.id
     }
 
     pub(crate) fn add_component(&mut self, component_index: usize) {

crates/comet_ecs/src/prefabs.rs

@@ -1,6 +1,6 @@
 use comet_structs::FlatMap;
 
-pub type PrefabFactory = fn(&mut crate::Scene) -> usize;
+pub type PrefabFactory = fn(&mut crate::Scene) -> crate::EntityId;
 
 pub(crate) struct PrefabManager {
     pub(crate) prefabs: FlatMap<String, PrefabFactory>,
@@ -26,8 +26,8 @@ impl PrefabManager {
 macro_rules! register_prefab {
     ($scene:expr, $name:expr, $($component:expr),* $(,)?) => {
         {
-            fn prefab_factory(scene: &mut $crate::Scene) -> usize {
-                let entity = scene.new_entity() as usize;
+            fn prefab_factory(scene: &mut $crate::Scene) -> $crate::EntityId {
+                let entity = scene.new_entity();
                 $(
                     scene.add_component(entity, $component);
                 )*

crates/comet_ecs/src/scene.rs

@@ -1,6 +1,6 @@
 use crate::archetypes::Archetypes;
 use crate::prefabs::PrefabManager;
-use crate::{Component, Entity, IdQueue};
+use crate::{Component, Entity, EntityId, IdQueue};
 use comet_log::*;
 use comet_structs::*;
 use std::any::TypeId;
@@ -8,6 +8,7 @@ use std::any::TypeId;
 pub struct Scene {
     id_queue: IdQueue,
     next_id: u32,
+    generations: Vec<u32>,
     entities: Vec<Option<Entity>>,
     components: ComponentStorage,
     archetypes: Archetypes,
@@ -19,6 +20,7 @@ impl Scene {
         Self {
             id_queue: IdQueue::new(),
             next_id: 0,
+            generations: Vec::new(),
             entities: Vec::new(),
             components: ComponentStorage::new(),
             archetypes: Archetypes::new(),
@@ -43,48 +45,78 @@ impl Scene {
         }
     }
 
+    fn is_alive(&self, id: EntityId) -> bool {
+        self.generations
+            .get(id.index as usize)
+            .is_some_and(|g| *g == id.gen)
+            && self
+                .entities
+                .get(id.index as usize)
+                .is_some_and(|e| e.is_some())
+    }
+
     /// Retuns the `Vec` of `Option<Entity>` which contains all the entities in the current Scene.
     pub fn entities(&self) -> &Vec<Option<Entity>> {
         &self.entities
     }
 
     /// Creates a new entity and returns its ID.
-    pub fn new_entity(&mut self) -> u32 {
-        let id = self.next_id;
-        if (self.next_id as usize) >= self.entities.len() {
-            self.entities.push(Some(Entity::new(self.next_id)));
-            self.get_next_id();
-            info!("Created entity! ID: {}", id);
-            return id;
+    pub fn new_entity(&mut self) -> EntityId {
+        let index = self.next_id;
+        let gen = if (index as usize) >= self.generations.len() {
+            self.generations.push(0);
+            0
+        } else {
+            self.generations[index as usize]
+        };
+
+        if (index as usize) >= self.entities.len() {
+            self.entities.push(Some(Entity::new(index, gen)));
+        } else {
+            self.entities[index as usize] = Some(Entity::new(index, gen));
         }
-        self.entities[self.next_id as usize] = Some(Entity::new(self.next_id));
+
+        let id = EntityId { index, gen };
         self.get_next_id();
-        info!("Created entity! ID: {}", id);
+        info!("Created entity! ID: {} (gen {})", id.index, id.gen);
         id
     }
 
     /// Gets an immutable reference to an entity by its ID.
-    pub fn get_entity(&self, entity_id: usize) -> Option<&Entity> {
-        self.entities.get(entity_id).unwrap().as_ref()
+    pub fn get_entity(&self, entity_id: EntityId) -> Option<&Entity> {
+        if !self.is_alive(entity_id) {
+            return None;
+        }
+        self.entities
+            .get(entity_id.index as usize)
+            .and_then(|e| e.as_ref())
     }
 
     /// Gets a mutable reference to an entity by its ID.
-    pub fn get_entity_mut(&mut self, entity_id: usize) -> Option<&mut Entity> {
-        self.entities.get_mut(entity_id).unwrap().as_mut()
+    pub fn get_entity_mut(&mut self, entity_id: EntityId) -> Option<&mut Entity> {
+        if !self.is_alive(entity_id) {
+            return None;
+        }
+        self.entities
+            .get_mut(entity_id.index as usize)
+            .and_then(|e| e.as_mut())
     }
 
     /// Deletes an entity by its ID.
-    pub fn delete_entity(&mut self, entity_id: usize) {
-        self.remove_entity_from_archetype_subsets(
-            entity_id as u32,
-            self.get_component_set(entity_id),
-        );
-        self.entities[entity_id] = None;
-        info!("Deleted entity! ID: {}", entity_id);
-        for (_, value) in self.components.iter_mut() {
-            value.remove::<u8>(entity_id);
+    pub fn delete_entity(&mut self, entity_id: EntityId) {
+        if !self.is_alive(entity_id) {
+            return;
         }
-        self.id_queue.sorted_enqueue(entity_id as u32);
+
+        let idx = entity_id.index as usize;
+        self.remove_entity_from_archetype(entity_id.index, self.get_component_set(idx));
+        self.entities[idx] = None;
+        info!("Deleted entity! ID: {}", entity_id.index);
+        self.components.remove_entity(idx);
+        if let Some(gen) = self.generations.get_mut(idx) {
+            *gen = gen.wrapping_add(1);
+        }
+        self.id_queue.sorted_enqueue(entity_id.index);
         self.get_next_id();
     }
 
@@ -107,24 +139,6 @@ impl Scene {
         }
     }
 
-    fn get_keys(&self, components: ComponentSet) -> Vec<ComponentSet> {
-        let component_sets = self.archetypes.component_sets();
-        component_sets
-            .iter()
-            .enumerate()
-            .filter_map(|(i, &ref elem)| {
-                if elem.is_subset(&components) {
-                    Some(i)
-                } else {
-                    None
-                }
-            })
-            .collect::<Vec<usize>>()
-            .iter()
-            .map(|index| component_sets[*index].clone())
-            .collect::<Vec<ComponentSet>>()
-    }
-
     fn add_entity_to_archetype(&mut self, entity_id: u32, components: ComponentSet) {
         self.archetypes
             .add_entity_to_archetype(&components, entity_id);
@@ -135,18 +149,6 @@ impl Scene {
             .remove_entity_from_archetype(&components, entity_id);
     }
 
-    fn remove_entity_from_archetype_subsets(&mut self, entity_id: u32, components: ComponentSet) {
-        let keys = self.get_keys(components);
-
-        for key in keys {
-            self.remove_entity_from_archetype(entity_id, key.clone());
-            if self.archetypes.get_archetype(&key).unwrap().len() == 0 {
-                self.archetypes.remove_archetype(&key);
-            }
-        }
-        info!("Removed entity {} from all archetypes!", entity_id);
-    }
-
     fn get_component_set(&self, entity_id: usize) -> ComponentSet {
         let components = match self.entities.get(entity_id) {
             Some(cmp) => match cmp.as_ref() {
@@ -192,120 +194,152 @@ impl Scene {
 
     /// Adds a component to an entity by its ID and an instance of the component.
     /// Overwrites the previous component if another component of the same type is added.
-    pub fn add_component<C: Component + 'static>(&mut self, entity_id: usize, component: C) {
-        let old_component_set = self.get_component_set(entity_id);
-        if !old_component_set.to_vec().is_empty() {
-            self.remove_entity_from_archetype_subsets(entity_id as u32, old_component_set);
+    pub fn add_component<C: Component + 'static>(&mut self, entity_id: EntityId, component: C) {
+        if !self.is_alive(entity_id) {
+            error!(
+                "Attempted to add component {} to dead entity {}",
+                C::type_name(),
+                entity_id.index
+            );
+            return;
         }
 
-        self.components.set_component(entity_id, component);
-        let component_index = self
+        let old_component_set = self.get_component_set(entity_id.index as usize);
+        if !old_component_set.to_vec().is_empty() {
+            self.remove_entity_from_archetype(entity_id.index, old_component_set);
+        }
+
+        self.components
+            .set_component(entity_id.index as usize, component);
+        if let Some(component_index) = self
             .components
             .keys()
-            .iter_mut()
+            .iter()
             .position(|x| *x == C::type_id())
-            .unwrap();
-        self.get_entity_mut(entity_id)
-            .unwrap()
-            .add_component(component_index);
+        {
+            if let Some(entity) = self.get_entity_mut(entity_id) {
+                entity.add_component(component_index);
+            } else {
+                error!(
+                    "Attempted to add component to non-existent entity {}",
+                    entity_id.index
+                );
+            }
+        } else {
+            error!(
+                "Component {} not registered, cannot add to entity {}",
+                C::type_name(),
+                entity_id.index
+            );
+        }
 
-        let new_component_set = self.get_component_set(entity_id);
+        let new_component_set = self.get_component_set(entity_id.index as usize);
 
         if !self.archetypes.contains_archetype(&new_component_set) {
             self.create_archetype(new_component_set.clone());
         }
 
-        let subsets = ComponentSet::compute_subsets_up_to_size_3(new_component_set.to_vec());
-
-        for subset in subsets {
-            if !self.archetypes.contains_archetype(&subset) {
-                self.create_archetype(subset.clone());
-            }
-
-            self.add_entity_to_archetype(entity_id as u32, subset);
-        }
+        self.add_entity_to_archetype(entity_id.index, new_component_set);
 
         info!(
             "Added component {} to entity {}!",
             C::type_name(),
-            entity_id
+            entity_id.index
         );
     }
 
-    pub fn remove_component<C: Component + 'static>(&mut self, entity_id: usize) {
-        let old_component_set = self.get_component_set(entity_id);
-        self.remove_entity_from_archetype_subsets(entity_id as u32, old_component_set);
+    pub fn remove_component<C: Component + 'static>(&mut self, entity_id: EntityId) {
+        if !self.is_alive(entity_id) {
+            return;
+        }
+        let old_component_set = self.get_component_set(entity_id.index as usize);
+        self.remove_entity_from_archetype(entity_id.index, old_component_set);
 
-        self.components.remove_component::<C>(entity_id);
-        let component_index = self
+        self.components
+            .remove_component::<C>(entity_id.index as usize);
+        if let Some(component_index) = self
             .components
             .keys()
             .iter()
             .position(|x| *x == C::type_id())
-            .unwrap();
-        self.get_entity_mut(entity_id)
-            .unwrap()
-            .remove_component(component_index);
+        {
+            if let Some(entity) = self.get_entity_mut(entity_id) {
+                entity.remove_component(component_index);
+            }
+        }
 
-        let new_component_set = self.get_component_set(entity_id);
+        let new_component_set = self.get_component_set(entity_id.index as usize);
 
         if !new_component_set.to_vec().is_empty() {
             if !self.archetypes.contains_archetype(&new_component_set) {
                 self.create_archetype(new_component_set.clone());
             }
 
-            let subsets = ComponentSet::compute_subsets_up_to_size_3(new_component_set.to_vec());
-
-            for subset in subsets {
-                if !self.archetypes.contains_archetype(&subset) {
-                    self.create_archetype(subset.clone());
-                }
-
-                self.add_entity_to_archetype(entity_id as u32, subset);
-            }
+            self.add_entity_to_archetype(entity_id.index, new_component_set);
         }
 
         info!(
             "Removed component {} from entity {}!",
             C::type_name(),
-            entity_id
+            entity_id.index
         );
     }
 
     /// Returns a reference to a component of an entity by its ID.
-    pub fn get_component<C: Component + 'static>(&self, entity_id: usize) -> Option<&C> {
-        self.components.get_component::<C>(entity_id)
+    pub fn get_component<C: Component + 'static>(&self, entity_id: EntityId) -> Option<&C> {
+        if !self.is_alive(entity_id) {
+            return None;
+        }
+        self.components
+            .get_component::<C>(entity_id.index as usize)
     }
 
     pub fn get_component_mut<C: Component + 'static>(
         &mut self,
-        entity_id: usize,
+        entity_id: EntityId,
     ) -> Option<&mut C> {
-        self.components.get_component_mut::<C>(entity_id)
+        if !self.is_alive(entity_id) {
+            return None;
+        }
+        self.components
+            .get_component_mut::<C>(entity_id.index as usize)
     }
 
-    pub fn has<C: Component + 'static>(&self, entity_id: usize) -> bool {
-        self.components.get_component::<C>(entity_id).is_some()
+    pub fn has<C: Component + 'static>(&self, entity_id: EntityId) -> bool {
+        self.is_alive(entity_id)
+            && self
+                .components
+                .get_component::<C>(entity_id.index as usize)
+                .is_some()
     }
 
     /// Returns a list of entities that have the given components.
-    pub fn get_entities_with(&self, components: Vec<TypeId>) -> Vec<usize> {
+    pub fn get_entities_with(&self, components: Vec<TypeId>) -> Vec<EntityId> {
         let component_set = ComponentSet::from_ids(components);
-        if component_set.size() > 3 {
-            error!("An entity query should only contain at most 3 different components!");
-            return Vec::new();
+        let mut result = Vec::new();
+
+        for archetype_set in self.archetypes.component_sets() {
+            if component_set.is_subset(archetype_set) {
+                if let Some(entities) = self.archetypes.get_archetype(archetype_set) {
+                    for index in entities.iter() {
+                        if let Some(gen) = self.generations.get(*index as usize) {
+                            if self
+                                .entities
+                                .get(*index as usize)
+                                .is_some_and(|e| e.is_some())
+                            {
+                                result.push(EntityId {
+                                    index: *index,
+                                    gen: *gen,
+                                });
                             }
-        if self.archetypes.contains_archetype(&component_set) {
-            return self
-                .archetypes
-                .get_archetype(&component_set)
-                .unwrap()
-                .clone()
-                .iter()
-                .map(|x| *x as usize)
-                .collect();
                         }
-        Vec::new()
+                    }
+                }
+            }
+        }
+
+        result
     }
 
     /// Deletes all entities that have the given components.
@@ -317,14 +351,31 @@ impl Scene {
     }
 
     /// Iterates over all entities that have the two given components and calls the given function.
-    pub fn foreach<C: Component, K: Component>(&mut self, func: fn(&mut C, &mut K)) {
-        let entities = self.get_entities_with(vec![C::type_id(), K::type_id()]);
-        for entity in entities {
-            let c_ptr = self.get_component_mut::<C>(entity).unwrap() as *mut C;
-            let k_ptr = self.get_component_mut::<K>(entity).unwrap() as *mut K;
+    pub fn foreach<C: Component, K: Component>(&mut self, mut func: impl FnMut(&mut C, &mut K)) {
+        if std::any::TypeId::of::<C>() == std::any::TypeId::of::<K>() {
+            error!("foreach called with identical component types");
+            return;
+        }
 
-            unsafe {
-                func(&mut *c_ptr, &mut *k_ptr);
+        let required = ComponentSet::from_ids(vec![C::type_id(), K::type_id()]);
+        let (c_set, k_set) = self
+            .components
+            .get_two_mut(&C::type_id(), &K::type_id());
+
+        if let (Some(c_store), Some(k_store)) = (c_set, k_set) {
+            for archetype_set in self.archetypes.component_sets() {
+                if required.is_subset(archetype_set) {
+                    if let Some(entities) = self.archetypes.get_archetype(archetype_set) {
+                        for &idx in entities {
+                            let idx = idx as usize;
+                            if let (Some(c), Some(k)) =
+                                (c_store.get_mut::<C>(idx), k_store.get_mut::<K>(idx))
+                            {
+                                func(c, k);
+                            }
+                        }
+                    }
+                }
             }
         }
     }
@@ -335,7 +386,7 @@ impl Scene {
     }
 
     /// Spawns a prefab with the given name.
-    pub fn spawn_prefab(&mut self, name: &str) -> Option<usize> {
+    pub fn spawn_prefab(&mut self, name: &str) -> Option<EntityId> {
         if self.prefabs.has_prefab(name) {
             if let Some(factory) = self.prefabs.prefabs.get(&name.to_string()) {
                 let factory = *factory; // Copy the function pointer

crates/comet_renderer/src/camera.rs

@@ -18,7 +18,11 @@ impl CameraManager {
         self.cameras.get(self.active_camera).unwrap()
     }
 
-    pub fn update_from_scene(&mut self, scene: &comet_ecs::Scene, camera_entities: Vec<usize>) {
+    pub fn update_from_scene(
+        &mut self,
+        scene: &comet_ecs::Scene,
+        camera_entities: Vec<comet_ecs::EntityId>,
+    ) {
         self.cameras.clear();
 
         let mut cameras_with_priority: Vec<(RenderCamera, u8)> = Vec::new();

crates/comet_renderer/src/renderer2d.rs

@@ -11,6 +11,7 @@ use comet_math::{m4, v2};
 use comet_resources::{
     font::Font, graphic_resource_manager::GraphicResourceManager, texture_atlas::*, Texture, Vertex,
 };
+use std::collections::HashSet;
 use std::sync::Arc;
 use wgpu::util::DeviceExt;
 use winit::{dpi::PhysicalSize, window::Window};
@@ -61,6 +62,7 @@ pub struct Renderer2D<'a> {
     resource_manager: GraphicResourceManager,
     camera_manager: CameraManager,
     render_passes: Vec<RenderPass>,
+    cached_render_entities: Vec<comet_ecs::EntityId>,
     last_frame_time: std::time::Instant,
     delta_time: f32,
 }
@@ -744,16 +746,45 @@ impl<'a> Renderer2D<'a> {
             return;
         }
 
-        let mut entities = scene.get_entities_with(vec![
+        let unsorted_entities = scene.get_entities_with(vec![
             comet_ecs::Transform2D::type_id(),
             comet_ecs::Render2D::type_id(),
         ]);
 
+        let mut dirty_sort = self.cached_render_entities.len() != unsorted_entities.len();
+
+        if !dirty_sort {
+            let unsorted_set: HashSet<comet_ecs::EntityId> =
+                unsorted_entities.iter().copied().collect();
+            dirty_sort = self
+                .cached_render_entities
+                .iter()
+                .any(|e| !unsorted_set.contains(e));
+        }
+
+        if !dirty_sort {
+            dirty_sort = !self.cached_render_entities.windows(2).all(|w| {
+                let a = scene
+                    .get_component::<comet_ecs::Render2D>(w[0])
+                    .map(|r| r.draw_index());
+                let b = scene
+                    .get_component::<comet_ecs::Render2D>(w[1])
+                    .map(|r| r.draw_index());
+                matches!((a, b), (Some(da), Some(db)) if da <= db)
+            });
+        }
+
+        if dirty_sort {
+            let mut entities = unsorted_entities;
             entities.sort_by(|&a, &b| {
                 let ra = scene.get_component::<comet_ecs::Render2D>(a).unwrap();
                 let rb = scene.get_component::<comet_ecs::Render2D>(b).unwrap();
                 ra.draw_index().cmp(&rb.draw_index())
             });
+            self.cached_render_entities = entities;
+        }
+
+        let entities = self.cached_render_entities.clone();
 
         let texts = scene.get_entities_with(vec![
             comet_ecs::Transform2D::type_id(),
@@ -922,7 +953,7 @@ impl<'a> Renderer2D<'a> {
         }
     }
 
-    fn setup_camera(&mut self, scene: &comet_ecs::Scene, cameras: Vec<usize>) {
+    fn setup_camera(&mut self, scene: &comet_ecs::Scene, cameras: Vec<comet_ecs::EntityId>) {
         if cameras.is_empty() {
             return;
         }
@@ -1012,6 +1043,7 @@ impl<'a> Renderer for Renderer2D<'a> {
             resource_manager: GraphicResourceManager::new(),
             camera_manager: CameraManager::new(),
             render_passes: Vec::new(),
+            cached_render_entities: Vec::new(),
             last_frame_time: std::time::Instant::now(),
             delta_time: 0.0,
         }

crates/comet_structs/src/column.rs

@@ -272,6 +272,33 @@ impl Column {
         }
     }
 
+    /// Remove an element without knowing its concrete type. Drops in place.
+    pub fn remove_any(&mut self, index: usize) {
+        if index >= self.data.len() {
+            return;
+        }
+        unsafe {
+            let ptr = self.data.swap_remove_and_forget_unchecked(index);
+            (self.data.drop)(ptr);
+        }
+    }
+
+    /// Overwrites an existing element in place, dropping the previous value.
+    pub fn set<T: 'static>(&mut self, index: usize, item: T) -> Option<()> {
+        assert_eq!(TypeId::of::<T>(), TypeId::of::<T>(), "Type mismatch");
+        if index >= self.data.len() {
+            return None;
+        }
+
+        unsafe {
+            let ptr = self.data.get_unchecked_mut(index) as *mut T;
+            ptr::drop_in_place(ptr);
+            ptr::write(ptr, item);
+        }
+
+        Some(())
+    }
+
     pub fn swap(&mut self, index1: usize, index2: usize) {
         assert!(
             index1 < self.data.len() && index2 < self.data.len(),

crates/comet_structs/src/component_storage.rs

@@ -55,4 +55,11 @@ impl ComponentStorage {
             None
         }
     }
+
+    /// Removes all components belonging to the given entity index.
+    pub fn remove_entity(&mut self, index: usize) {
+        for (_, value) in self.iter_mut() {
+            value.remove_any(index);
+        }
+    }
 }

crates/comet_structs/src/componet_set.rs

@@ -67,6 +67,10 @@ impl ComponentSet {
         self.set.is_subset(&other.set)
     }
 
+    pub fn is_superset(&self, other: &ComponentSet) -> bool {
+        self.set.is_superset(&other.set)
+    }
+
     pub fn to_vec(&self) -> Vec<TypeId> {
         self.set.iter().cloned().collect()
     }

crates/comet_structs/src/flat_map.rs

@@ -44,6 +44,39 @@ impl<K: PartialEq + Clone, V: Clone> FlatMap<K, V> {
         }
     }
 
+    pub fn get_two_mut(&mut self, a: &K, b: &K) -> (Option<&mut V>, Option<&mut V>) {
+        if a == b {
+            let first = self.get_mut(a);
+            return (first, None);
+        }
+
+        let mut first_index = None;
+        let mut second_index = None;
+
+        for (idx, (key, _)) in self.map.iter().enumerate() {
+            if key == a {
+                first_index = Some(idx);
+            } else if key == b {
+                second_index = Some(idx);
+            }
+        }
+
+        match (first_index, second_index) {
+            (Some(i), Some(j)) => {
+                if i < j {
+                    let (left, right) = self.map.split_at_mut(j);
+                    (Some(&mut left[i].1), Some(&mut right[0].1))
+                } else {
+                    let (left, right) = self.map.split_at_mut(i);
+                    (Some(&mut right[0].1), Some(&mut left[j].1))
+                }
+            }
+            (Some(i), None) => (self.map.get_mut(i).map(|pair| &mut pair.1), None),
+            (None, Some(j)) => (None, self.map.get_mut(j).map(|pair| &mut pair.1)),
+            _ => (None, None),
+        }
+    }
+
     pub fn contains(&self, key: &K) -> bool {
         self.map.iter().any(|node| node.0 == *key)
     }

crates/comet_structs/src/sparse_set.rs

@@ -28,6 +28,12 @@ impl SparseSet {
         }
 
         if let Some(page_vec) = &mut self.sparse[page] {
+            // If there is already a mapping, overwrite the existing dense value instead of pushing.
+            if let Some(sparse_index) = page_vec[index % self.page_size] {
+                let _ = self.dense.set::<T>(sparse_index, value);
+                return;
+            }
+
             page_vec[index % self.page_size] = Some(self.dense.data.len());
         }
 
@@ -69,6 +75,64 @@ impl SparseSet {
         None
     }
 
+    /// Removes an element by external index without knowing its type. Returns true if something was removed.
+    pub fn remove_any(&mut self, index: usize) -> bool {
+        if let Some(page_vec) = self
+            .sparse
+            .get(index / self.page_size)
+            .and_then(|x| x.as_ref())
+        {
+            if let Some(sparse_index) = page_vec
+                .get(index % self.page_size)
+                .and_then(|x| x.as_ref())
+            {
+                let dense_index = *sparse_index;
+                let last_dense_index = self.dense.data.len() - 1;
+
+                if dense_index != last_dense_index {
+                    if let Some(ext_index) = self.find_external_index(last_dense_index) {
+                        if let Some(page_vec) = self
+                            .sparse
+                            .get_mut(ext_index / self.page_size)
+                            .and_then(|x| x.as_mut())
+                        {
+                            page_vec[ext_index % self.page_size] = Some(dense_index);
+                        }
+                    }
+                    self.dense.swap(dense_index, last_dense_index);
+                }
+
+                if let Some(page_vec) = self
+                    .sparse
+                    .get_mut(index / self.page_size)
+                    .and_then(|x| x.as_mut())
+                {
+                    page_vec[index % self.page_size] = None;
+                }
+
+                self.dense.remove_any(dense_index);
+                return true;
+            }
+        }
+        false
+    }
+
+    /// Finds the external index that maps to a given dense index.
+    fn find_external_index(&self, dense_index: usize) -> Option<usize> {
+        for (page_idx, page_opt) in self.sparse.iter().enumerate() {
+            if let Some(page) = page_opt {
+                for (offset, entry) in page.iter().enumerate() {
+                    if let Some(idx) = entry {
+                        if *idx == dense_index {
+                            return Some(page_idx * self.page_size + offset);
+                        }
+                    }
+                }
+            }
+        }
+        None
+    }
+
     pub fn get<T: 'static>(&self, index: usize) -> Option<&T> {
         if let Some(page_vec) = self
             .sparse