Building Eisen Engine: Architecture of a Custom C++20 Game Engine from Scratch (Vulkan, ECS & AI Subsystems)

TL;DR: Commercial game engines like Unreal Engine and Unity carry millions of lines of legacy code, runtime garbage collection spikes, and deep OOP class hierarchies that hinder low-latency AI workflows. This article details the full architectural design of Eisen Engine—a high-performance, modular C++20 game engine featuring explicit Vulkan/OpenGL rendering abstractions, a cache-aligned Entity Component System (ECS), lock-free event dispatching, and embedded AI-native tick loops.

1. Why Build a Custom Game Engine from Scratch?

In modern game development, standard commercial engines offer convenience at the cost of control:

Monolithic Bloat: Even empty starter projects in modern engines compile to hundreds of megabytes of binary dependencies.

Cache Inefficiency: Object-oriented architectures (Actor -> Pawn -> Character) scatter entity data across disconnected heap locations, triggering severe CPU L1/L2 cache misses.