Fomalhaut

Fomalhaut

A clean, simple, c++14, Entity Component System like Overwatch ECS architecture

Overview

This is a simple entity component system library based on the Overwatch Gameplay Architecture and Netcode article. It is written in c++14 without other dependencies. You can easily add include-folder into your game project.

NOTE:

This is my thought about how the 'Overwatch' ECS should look. If you want to add it to a commercial project, you'd better read the source code and master it. Then add the features that you need.

Support(Need C++14)

• gcc >= v5 (tested with v5.4.0)
• clang
• MSVC >= VS2015

Installation

1. Git pull source code
2. cd Fomalhaut && mkdir build
3. Run ./run.sh

Tutorial

Create An EntityAdmin

EntityAdmin controlls all entities and systems. You can simply define it by the following code:

<pre><code>EntityAdmin admin; </code></pre>

Create Component

Declare some components that derived from BaseComponent such as:

<pre><code>class MovementComponent : public BaseComponent { public: void Reset(float velocity) { this->velocity = velocity; } void Print() { std::cout << "MovementComponent: " << velocity << std::endl; } float velocity; }; class HealthComponent : public BaseComponent { public: void Reset(float hp, float mana) { this->hp = hp; this->mana = mana; } void Print() { std::cout << "HealthComponent: " << hp << '\t' << mana << std::endl; } float hp, mana; }; class PositionComponent : public BaseComponent { public: void Reset(float px, float py, float pz) { x = px; y = py; z = pz; } void Print() { std::cout << "PositionComponent: " << x << '\t' << y << '\t' << z << std::endl; } float x, y, z; }; </code></pre>

Create An Entity

Entity is an aggregate that consists of one or more components. It was created by An EntityAdmin.

<pre><code>Entity& entity = admin.CreateEntity&lt;Entity>();</code></pre>

You can simply add or replace component by:

<pre><code>entity.Add&lt;PositionComponent>(3.f, 7.f, 10.f); entity.Replace&lt;PositionComponent>(10.f, 100.f, 100.f); </code></pre>

To check whether entity has any components:

<pre><code>bool result = entity.Has&lt;HealthComponent>(); bool result = entity.Has&lt;PositionComponent, HealthComponent>(); </code></pre>

Remove one or more components:

<pre><code>entity.Remove&lt;PositionComponent>(); entity.Remove&lt;PositionComponent, HealthComponent>(); </code></pre>

Use tuple to get some componets one-time:

<pre><code>PositionComponent* p = entity.Get&lt;PositionComponent>(); std::tuple&lt;PositionComponent*, HealthComponent*> va1 = entity.Get&lt;PositionComponent, HealthComponent>(); </code></pre>

Create A Demosystem And Iterate Components

<pre><code>class DemoSystem : public BaseSystem { public: using BaseSystem::BaseSystem; void Update(float time_step) override { for (PositionComponent* p : ComponentItr&lt;PositionComponent>(admin_)) { p->Print(); HealthComponent* h = p->Sibling&lt;HealthComponent>(); if (h) { h->Print(); } MovementComponent* m = p->Sibling&lt;MovementComponent>(); if (m) { m->Print(); } } } }; DemoSystem& sys = admin.CreateSystem&lt;DemoSystem>(); sys.Update(0.1f); </code></pre>

Use tuple-iterator to iterate Entity that has specific components with specific condition:

<pre><code>for (std::tuple&lt;PositionComponent*, HealthComponent*>&& t : ComponentItr&lt;PositionComponent, HealthComponent>( &admin, [](const PositionComponent*p, const HealthComponent* h) -> bool { return h->hp > 60; })) { std::get&lt;0>(t)->Print(); std::get&lt;1>(t)->Print(); }</code></pre>