C++ Game Engine Basics: ECS, Rendering, Physics, Input, Lua [#50-3]

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C++ Game Engine Basics: ECS, Rendering, Physics, Input, Lua [#50-3]

이 글의 핵심

Entity-Component-System, sprite render with z-order, simple AABB physics and collision response, input, and Lua integration for gameplay scripts.

Introduction

Without Unity/Unreal you still need stable simulation, draw order, responsive input, and scriptable logic. This article sketches ECS, 2D rendering (SDL2/SFML), AABB physics, input, and Lua embedding.

Goals: ECS layout, render pipeline with z-index, gravity + collision resolution, input + callbacks, Lua bindings (high level).

Requirements: C++17, SDL2 or SFML, optional Box2D, Lua 5.4.

ECS

  • Entity = id + map type_index → unique_ptr.
  • Transform, Sprite, RigidBody, Collider components.
  • Systems: RenderSystem (sort by z), PhysicsSystem (integrate + resolve), InputSystem.

Note: Naive get_entities_with each frame allocates—production engines use archetypes or sparse sets.

Rendering

  • Clear → sort sprites by z_index → SDL_RenderCopyEx → present.

Physics (simple)

  • Apply gravity → integrate positions → pairwise AABB test → resolve (bounce/swap velocities); triggers skip impulse.

Input

  • Poll keys; optional event callbacks for UI.

Scripting

  • Lua loads game data / rules; bind C++ functions with sol2 or C API (article-level detail).
  • Game engine architecture
  • Earlier game engine intro

Summary

ECS + sorted render + simple AABB gives a teachable 2D loop. Profile and replace hot paths (allocation, collision broadphase) as the project grows.