A WIP 2D game engine utilizing an Entity-Component-System(ECS) architecture, built in C++.
OpenGL for rendering, GLFW for window creation, Eigen for vector/matrix math, Glad for OpenGL loading, irrKlang for audio, and stb for image loading.
First create a game, specifying the window width and height.
Game myGame(800, 600);
You can add resources such as textures with the ResourceEngine. We utilize a service locator to provide access to these sub-engines.
Locator::getResourceEngine()->addTexture("mySprite.png", "mySprite");
You will fill your game with Entities, which can take on a variety of forms. Their form depends on which components are applied to them. Components give entities specific properties like a collision-shape or sprite. Note that an entity with applied components does nothing on its own.
Entity* e = new Entity();
e->applyComponent<Sprite>(Locator::getResourceEngine()->getTexture("mySprite");
e->applyComponent<gTransform>(Eigen::Vector3f(0,0,0));
Systems make your game come alive by acting on different entities. Which entities a given system acts on depends on which components it has.
myGame.addSystem(new SpriteRenderSystem());
Finally, start the game.
myGame.start();
Below we find the Sprite component used above. Note that the component has no functionality other than storing data. Derive from Component to create a new component.
struct Sprite : public Component {
Sprite(Texture* texture, Eigen::Vector2f origin = Eigen::Vector2f::Zero()) : texture(texture), origin(origin) {};
Texture* texture;
Eigen::Vector2f origin;
};
Here is the SpriteRenderSystem used above. Note that it acts only on entities with Sprite and gTransform components applied. The filtering is performed in the base class using std::bitset. Derive from System to create a new system. You should define init to add required components and execute to apply behaviours.
class SpriteRenderSystem : public System {
public:
void init() {
addRequiredComponent<Sprite>();
addRequiredComponent<gTransform>();
renderEngine_ = Locator::getRenderEngine();
ioEngine_ = Locator::getIOEngine();
}
private:
RenderEngine* renderEngine_;
IOEngine* ioEngine_;
void execute(Entity* e, const float dt) {
gTransform* t = e->getComponent<gTransform>();
renderEngine_->drawTexture(e->getComponent<Sprite>()->texture, t->position, t->scale, t->rotation);
}
};