Entity Component System (ECS)
Almost everything that exists in the game is an entity, from the player and NPCs to the map terrain and UI. An entity doesn't do much on it's own, but acts as a container to add components to. This is a common pattern in game development called an Entity Component System (ECS). Each component is responsible for one piece of functionality. We can make an entity do something interesting with the right combination of components.
For example, to create a tree:
public static Entity createTree() {
Entity tree = new Entity()
.addComponent(new TextureRenderComponent("images/tree.png"))
.addComponent(new PhysicsComponent())
.addComponent(new ColliderComponent());
return tree;
}
- We start with a new entity
- We add a
TextureRenderComponent
which draws the tree texture on screen - We add a
PhysicsComponent
which lets the tree use game physics - We add a
ColliderComponent
which adds a rectangular collider around the tree, so other physics entities can't walk through it.
The tree would look like this in the game (green border indicates physics collider):
A simple player entity might look like:
public static Entity createPlayer() {
return new Entity()
.addComponent(new TextureRenderComponent("images/player.png"))
.addComponent(new PlayerMovementComponent())
.addComponent(new InventoryComponent())
.addComponent(new CombatComponent());
}
We can reuse the same texture render component that we used for the tree, but also add player-specific components to control movement, give the player an inventory, and give them combat capabilities (e.g. health and attack damage).
Inheritance has some strong limitations, both in game development and general software development. Inheritance only allows for change along one axis. This explanation of the bridge pattern has a great explanation of how this leads to problems. For an example that relates to game development, consider this inheritance tree for enemies:
If the scope of the project changes, and we now want to add a FlyingRangedEnemy
, we are in trouble. The flying code exists in an entirely different part of the inheritance tree! In this case, composition (e.g. the bridge pattern) can be used to extract the flight code into a separate class, which both FlyingRangedEnemy
and FlyingMeleeEnemy
can use.
ECS can be considered as simply the bridge pattern taken one step further, where entity behaviour is defined completely by composition. The core entity class only contains functionality that is required for every entity in the game, and is never extended from. In general, it is recommended to keep inheritance trees wide rather than deep, and use composition where possible.
- Article explaining ECS
- Game Engine Architecture, 3rd Edition, Chapter 16.2
- Famous talk on Data-Oriented Programming: One step beyond ECS, we can throw away the idea of representing data as objects. Data-Oriented programming can create very performant code and is gaining traction in game development.
- Unity Engine's Data-Oriented Implementation
Camera Angle and The Player's Perspective
Achievements Trophies and Cards
πΎ Obstacle/Enemy
βMonster Manual
βObstacles/Enemies
ββ- Alien Plants
ββ- Variation thorns
ββ- Falling Meteorites
ββ- FaceHugger
ββ- AlienMonkey
βSpaceship & Map Entry
βParticle effect
[code for debuff animations](code for debuff animations)
Main Character Movement, Interactions and Animations - Code Guidelines
ItemBar & Recycle system
πΎ Obstacle/Enemy
βObstacle/Enemy
βMonster Manual
βSpaceship Boss
βParticle effects
βOther Related Code
βUML & Sequence diagram of enemies/obstacles
Scoring System Implementation Explanation
Buff and Debuff Implementation
Infinite generating terrains Implementation Explanation
Game Over Screen and functions explaination
Buffer timer before game start
Rocks and woods layout optimization
Magma and nails code implementation
Guide: Adding Background music for a particular screen
History Scoreboard - Score Details
Listening for important events in the Achievements ecosystem
Hunger and Thirst icon code guidelines
Hunger and Thirst User Testing
Buff and Debuff Manual User Testing
The New Button User Test in Setting Page
The Main Menu Buttons User Testing
Infinite loop game and Terrain Testing
https://github.com/UQdeco2800/2021-ext-studio-2.wiki.git
πΎ Obstacle/Enemy
βObstacle testing
ββ- Alien Plants & Variation Thorns
ββ- Falling Meteorites
βEnemy testing
ββ- Alien Monkeys & Facehugger
ββ- Spaceship Boss
βMonster Manual
βParticle-effect
βPlayer attack testing
ββ- Player Attack
Sprint 1
Sprint 2
Sprint 3
Sprint 4
Changeable background & Buffer time testing
Game over screen test sprint 4
New terrain textures on bonus map test sprint 4
Achievements System, Game Records and Unlockable Chapters
Musics Implementation Testing plan