Hazel game engine (077) introduces EnTT

If there are errors in the code, terminology, etc. in the text, please correct me

foreword

• of this program

  Use the test Entt library to provide an API for ECS mode

• Entt library

  • why use it

    • Write your own ECS trouble

    • Excellent

  • address

    click here

Entt integrated into the project

1. Open Entt address

2. Click on single_include

   

3. Copy entt.hpp to the project (note the path)

   

4. Include entt.hpp in the premake.lua file

   IncludeDir["entt"] = "GameEngineLightWeight/vendor/entt/include"
   ......
   includedirs{
         
         
   ......
   "%{IncludeDir.stb_image}",
   "%{IncludeDir.entt}"
   }
   

basic use

#pragma once

#include "entt.hpp"
namespace Hazel {
    
    
	class Scene
	{
    
    
	public:
		Scene();
		~Scene();
		
	private:
		entt::registry m_Registry;
	};
}

#include "hzpch.h"
#include "Scene.h"
#include "glm/glm.hpp"
namespace Hazel {
    
    
    static void DoMath(const glm::mat4& transform) {
    
    

    }
    static void OnTransformConstruct(entt::registry& registry, entt::entity entity) {
    
    

    }
    Scene::Scene()
    {
    
    
        struct TransformComponent {
    
     // 不用继承Component
            glm::mat4 Transform;
            TransformComponent() = default;
            TransformComponent(const TransformComponent&) = default;
            TransformComponent(const glm::mat4& transform)
                : Transform(transform){
    
    }
            operator const glm::mat4& () {
    
     return Transform; }
        };
        struct MeshComponent {
    
    
            glm::mat4 Transform;
            MeshComponent() = default;
            MeshComponent(const MeshComponent&) = default;
            MeshComponent(const glm::mat4& transform)
                : Transform(transform) {
    
    }
            operator const glm::mat4& () {
    
     return Transform; }
        };
        TransformComponent transform;
        // 测试
        DoMath(transform.Transform);
        DoMath(transform); // 因为有类型转换函数
        // 若没有类型转换函数
        DoMath(*(glm::mat4*)&transform);

        // 1.创建一个实体,返回整数 id
        entt::entity entity = m_Registry.create(); // 是uint32_t
        // 2.实体放入TransformComponent组件.arg1:id，arg2：glm会转换为TransformComponent
        m_Registry.emplace<TransformComponent>(entity, glm::mat4(1.0f));
        // 3.判断实体是否有哦TransformComponent组件
        //if (m_Registry.has<TransformComponent>(entity))  // 代码报错不知道为什么
        // 4.获取实体的TransformComponent组件,根据id
        TransformComponent& transform = m_Registry.get<TransformComponent>(entity);
        // 5.m_Registry已注册的所有TransformComponent组件
        auto view = m_Registry.view<TransformComponent>();
        for (auto entity : view) {
    
    
            TransformComponent& transform1 = m_Registry.get<TransformComponent>(entity); // view、m_Registry两个都行
            TransformComponent& transform2 = view.get<TransformComponent>(entity);
        }
        // 6.m_Registry获取既有Transform组件又有Mesh组件的实体
        auto group = m_Registry.group<TransformComponent>(entt::get<MeshComponent>);
        for (auto entity : group) {
    
    
            auto&[transform, mesh] = group.get<TransformComponent, MeshComponent>(entity);
            //Renderer::Submit(mesh, transform);
        }
        // 7.设置当实体添加TransformComponent组件时执行OnTransformConstruct方法
        m_Registry.on_construct<TransformComponent>().connect<&OnTransformConstruct>();
    }
    Scene::~Scene()
    {
    
    
    }
}