Misaki
d8a7b07624
- Refactor D3D12 backend and RenderGraph module - Update graphics RHI and core rendering components - Add Random.hlsl shader include - Regenerate API documentation and update user guides
2.3 KiB
ECS Concepts
GhostEngine's ECS implementation relies on several key concepts rooted in Data-Oriented Design. Understanding these concepts is essential to writing performant engine code and gameplay logic.
World
A World encapsulates all data and logic for an independent ECS simulation. It owns three core managers:
- EntityManager: Handles the creation, destruction, and structural modification of Entities.
- ComponentManager: Manages Archetypes and EntityQueries, keeping track of component memory layouts and chunk allocations.
- SystemManager: Manages the lifecycle and execution order of all Systems.
Multiple Worlds can exist simultaneously (e.g., one for logic, one for rendering, or server/client splits in multiplayer).
Entity
An Entity in Ghost.Entities is not an object or a class; it is merely an integer ID (often accompanied by a version number). It serves as a lookup key to find a specific set of component data.
Component
A Component is a pure, unmanaged data structure (struct). It implements IComponent or IEnableableComponent. Components contain no logic. By restricting components to unmanaged types, the engine ensures they can be packed tightly into continuous blocks of memory (Chunks), entirely avoiding Garbage Collection (GC) overhead and ensuring fast CPU cache lines.
Archetype and Chunks
When you create an entity with a specific set of components (e.g., Position and Velocity), the ECS groups it into an Archetype. An Archetype represents a unique signature of components.
Entities of the same Archetype have their component data stored in Chunks. A Chunk is a fixed-size block of unmanaged memory (e.g., 16KB).
Instead of storing arrays of Entities containing objects (Array of Structures), the Chunk stores independent arrays for each component type (Structure of Arrays). This means when a system queries for Position, it receives a contiguous unmanaged memory Span<Position>, allowing the CPU to aggressively prefetch data and vectorize operations.
System
A System provides the logic that transforms component data from one state to the next. Systems iterate over matching Archetypes using EntityQuery and process component data in bulk. Systems can be managed manually or grouped into a SystemGroup which topologically sorts execution order based on dependencies.