A Glance of Game Engine Layers

工具层 Tool Layer
功能层 Function Layer
资源层 Resource Layer
核心层 Core Layer
平台层 Platform Layer
第三方库 3rd Party Libraries

Resource Layer

offline Resource Importing

resource->access 资源-》资产

• Unify file access by defining a meta asset file format
• Assets are faster to access by importing preprocess
• Build a composite asset file to refer to all resources
• GUID is an extra protection of reference
• 统一导入资源格式 使用更高效的格式
• 使用预处理更高效导入 ie.合并贴图
• 建立资源间链接
• 设置全局编号保护引用正确（防止资源路径变化

Runtime Resource Management

handle system
使用过程中的加载吧，没太懂，后面会具体介绍

Manage Asset Life Cycle

• Different resources have different life cycles
• Limited memory requires release of loaded resources when possible
• Garbage collection and deferred loading is critical features
• 生命周期控制的重要性
• 内存释放不到位造成卡顿
• 垃圾回收和延迟导入对流畅性至关重要

Function Layer

Key–Ticks

以帧率循环执行的函数 分为逻辑和渲染

• Fetch animation frame of character
• Drive the skeleton(骨架）and skin of character
• Render process all rendering jobs in an iteration of render tick for each frame
• Heavy-duty Hotchpotch（杂烩）
• Multi-Threading(Job sys)

void tickMain(float delta_time)
{
	while(!exit_flay)
	{
		tickLogic(delta_time);
		tickRender(delta_time);
	}
}

void tickLogic(float delta_time)
{
	tickCamera(delta_time);
	tickMotor(delta_time);
	tickController(delta_time);
	/*...*/
}
void tickRender(float delta_time)
{
	tickRenderCamera();
	rendering();
	postprocess();
	/*...*/
}

Core Layer

提供高效的底层工具

• Math Library
• Data Structure and Containers
• Memory Management
  -Polymorphic Memory Resource PMR 多态内存资源
  -Reduce cache miss
  -Put data together
  -Access data in order
  -Allocate and de-allocate as a block
  集中存放，按顺序获取，成组提取擦除

Platform Layer

Render Hardware Interface(RHI)适应不同硬件平台的着色器转换工具

Tool Layer

allow Anyone to create game
Asset Conditioning Pipeline(把其他平台工具应用到游戏引擎的管线(?)输入输出功能）

引擎分层作用

decoupling (解耦)and reducing complexity
Response for Evolving Demands
越底层越稳定，高层依赖于底层，不需要了解底层实现原理，高层更新频繁。

Conclusion

• 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