Entity System

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Entity Base

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Entity Lifecycle

pub trait EntityBase: Send + Sync + NBTStorage {
    fn tick<'a>(
        &'a self,
        caller: Arc<dyn EntityBase>,
        server: &'a Server,
    ) -> EntityBaseFuture<'a, ()>;
    
    fn init_data_tracker(&self) -> EntityBaseFuture<'_, ()>;
    
    fn teleport(
        self: Arc<Self>,
        position: Vector3<f64>,
        yaw: Option<f32>,
        pitch: Option<f32>,
        world: Arc<World>,
    ) -> TeleportFuture;
}

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Core Entity Properties

• Position & Rotation: Atomic position tracking
• Velocity: Physics-based movement
• Bounding Box: Collision detection
• Metadata: Synced entity data
• Age: Tick counter for entity lifecycle

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Entity Types

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Living Entities

pub struct LivingEntity {
    pub entity: Arc<Entity>,
    // Health, armor, attributes
}

• Players: Human-controlled entities
• Mobs: Hostile and neutral creatures
• Passive Mobs: Animals and friendly creatures

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Projectiles

• Arrows: Shot from bows/crossbows
• Snowballs: Throwable items
• Eggs: Thrown eggs
• Fireballs: Ghast/blaze projectiles
• Wind Charges: Breeze attacks
• Firework Rockets: Elytra propulsion

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Vehicles

• Boats: Water and chest boats
• Minecarts: Rail transport

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Other Entities

• Items: Dropped items (ItemEntity)
• Experience Orbs: XP drops
• TNT: Primed explosives
• Falling Blocks: Sand, gravel physics
• Armor Stands: Display entities
• Paintings: Decorative art
• End Crystals: End dimension entities

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Entity Spawning

world.spawn_from_type(
    entity_type: &'static EntityType,
    position: Vector3<f64>,
).await;

• EntityType::Zombie
• EntityType::Skeleton
• EntityType::Cow
• EntityType::Arrow

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Entity Metadata

pub struct Metadata {
    pub index: u8,
    pub metadata_type: MetaDataType,
    pub value: T,
}

• DATA_BABY: Baby entity flag
• DATA_CUSTOM_NAME: Entity display name
• DATA_HEALTH: Current health
• DATA_ARMOR: Armor value

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Mob AI System

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Goal System

pub struct GoalSelector {
    // Manages and executes AI goals
}

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Movement Goals

• WanderAround: Random exploration
• FollowParent: Baby animals follow adults
• FollowOwner: Tamed animals follow owner
• EscapeDanger: Flee from threats
• Swim: Prevent drowning

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Combat Goals

• MeleeAttack: Close-range combat
• ZombieAttack: Zombie-specific attack
• ChasePlayer: Enderman chase behavior
• Revenge: Target attackers
• ActiveTarget: Hunt specific entities

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Interaction Goals

• LookAtEntity: Face nearby entities
• LookAround: Ambient head movement
• Tempt: Follow player holding food
• Beg: Wolf begging behavior
• Breed: Animal breeding

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Special Goals

• CreeperIgnite: Creeper explosion
• EatGrass: Sheep grazing
• PickUpBlock: Enderman block pickup
• PlaceBlock: Enderman block placement
• DestroyEgg: Zombie turtle egg breaking

​

Pathfinding

pub struct WalkNodeEvaluator {
    // Evaluates path nodes for walking entities
}

pub struct PathfindingContext {
    // Context for pathfinding operations
}

• A Algorithm*: Efficient pathfinding
• Path Caching: Reuse computed paths
• Block Awareness: Navigate around obstacles
• Jump Detection: Navigate elevation changes

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Mob Types

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Hostile Mobs

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Zombies

• Zombie: Standard undead
• Zombie Villager: Curable zombie
• Husk: Desert variant
• Drowned: Underwater zombie

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Skeletons

• Skeleton: Bow-wielding undead
• Wither Skeleton: Nether variant
• Stray: Snow biome skeleton
• Bogged: Swamp skeleton
• Parched: Desert skeleton

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Other Hostiles

• Creeper: Explosive mob
• Enderman: Teleporting mob
• Silverfish: Small insect
• Bat: Ambient cave mob

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Passive Mobs

• Cow: Milk and beef source
• Pig: Rideable animal
• Sheep: Wool provider
• Chicken: Egg layer
• Cat: Tamed companion
• Wolf: Tamed protector

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Utility Mobs

• Iron Golem: Village protector
• Snow Golem: Snowball thrower

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Boss Mobs

• Wither: Three-headed boss

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Player Entity

pub struct Player {
    pub living_entity: Arc<LivingEntity>,
    pub gameprofile: GameProfile,
    pub config: ArcSwap<PlayerConfig>,
    pub world: Arc<World>,
    // Inventory, abilities, experience, etc.
}

• Gamemode: Survival, Creative, Adventure, Spectator
• Inventory: Item storage and hotbar
• Abilities: Flight, invulnerability
• Experience: Levels and points
• Hunger: Food and saturation
• Attributes: Health, speed, reach distance

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Entity Attributes

pub struct Attributes {
    pub max_health: f64,
    pub movement_speed: f64,
    pub attack_damage: f64,
    pub armor: f64,
    pub knockback_resistance: f64,
}

• Combat effectiveness
• Movement capabilities
• Survival stats

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Entity Effects

• Beneficial: Regeneration, Speed, Strength
• Harmful: Poison, Weakness, Slowness
• Mixed: Invisibility, Glowing

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Entity Combat

pub enum DamageType {
    Generic,
    Player,
    Mob,
    Projectile,
    Explosion,
    Fire,
    Fall,
    // ... more types
}

• Armor reduction
• Enchantment modifiers
• Invulnerability ticks
• Knockback calculation

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Projectile Deflection

pub trait ProjectileDeflection {
    fn can_deflect(&self) -> bool;
    fn deflect(&self, projectile: Arc<dyn EntityBase>);
}

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Network Synchronization

• CSpawnEntity: Initial entity spawn
• CUpdateEntityPos: Position updates
• CUpdateEntityPosRot: Position and rotation
• CUpdateEntityRot: Rotation only
• CSetEntityMetadata: Metadata changes
• CSetPassengers: Vehicle mounting
• CTeleportEntity: Teleportation

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Performance Optimizations

• Atomic Operations: Lock-free position/rotation updates
• Async Ticking: Non-blocking entity updates
• Spatial Partitioning: Efficient entity queries
• Packet Batching: Combine nearby entity updates