第二节：引擎架构分层

Layered Architecture of Game Engine

• Sea of Code

游戏引擎分层简介

Layers

• Tool Layer

• Function Layer

  • Physics

  • Animation

  • rendering

  • Camera HUD Input

  • Script FSM AI

• Resource Layer

  • Data and Files

• Core Layer

  • Swiss Knife of Game Engine

• Platform Layer

  • Launch on Different Platforms

  • Operation Systems

  • Platform File System

  • Platform SDK

• 3rd Party Libraries

5 + 1 层次涵盖了几乎所有引擎功能

Resource Layer

• How to Access My Data

  • Resource -> asset

  • Offline Resource Importing

  • 引擎的核心功能之一是资源关联

• Rentime Asset Manager

• Manage Asset Life Cycle

  • 生命周期管理

  • 延时加载

Function Layer

• How to Make the world alive

• 每个 Tick 进行一遍所有的系统执行

• 普朗克时间就是现实世界的 Tick

Dive into Tick

• tick main

  • tick logic 先世界模拟

  • tick render 再进行渲染

Heavy - duty Hotchpotch

• Function Layer provides major function modules for the game engine

• Game Loop updates the systems periodically

• Blur the boundary between engine and game

Multi-Threading

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难点在 Dependency 管理

Core Layer

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Math Library

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• math efficiency

• 倒数平方根很慢，quake 3 有一个近似算的很快

• SIMD ：专门做向量运算的组件，可以同时进行 4 次相加

Data Structure and Container

image-20220330204838371

• 需要重新写游戏引擎手动控制的容器数据结构，因为语言自带的托管内存的数据结构所占据的内存会产生很多空洞，内存的消耗是不可控的。

• 出现很多内存碎片，访问效率很低。

Memory Management 内存管理

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• 现代计算机的内存数据读写还是图灵机方式

• 需要有高效的内存分配模式

  • Put data together 数据在一块

  • Access data in order 数据按顺序读写

  • Allocate and de-allocate as a block 按照块状分配内存

Platform Layer

Target on Different Platform

需要做到平台无关性

• File system

• Graphic api , Render Hardware Interface (RHI) 重新定义一套渲染接口

  • Transparent different GPU architectures and SDK

  • Automatic optimization of target platforms

• Hardware Architecture 特定机器优化

Tool Layer

Allow Anyone to Create Game

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Manual Editors

• Level Editor

• Logical Editor

• Shader Editor

• Animation Editor

• UI Editor

• Flexible of coding languagesz

Digital Content Creation

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• 数字资产生产工具

• Asset conditioning pipeline，把资产导入引擎

• tool chains，工具链

Why Layered Architecture

• Decoupling and Reducing Complexity

  • Lower layers are independent from upper layers

  • Upper layers don't know how lower layers are implemented

• Response for Evolving Demands

  • Upper layers evolve fast, but lower layers are stable

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Mini Engine : Pilot

image-20220330211847914

Simple ECS framework

image-20220330212201585

Takeaways

• Engine is designed with a layered architecture

• Lower levels are more stable and upper levels are more customizable

• Virtual world is composed by a set of clocks - ticks