Ufdjrw

First of all, let me describe my terms/implementations.

Component contains just data about something. e.g.

class TransformComponent : public Component<TransformComponent> /*CRTP*/ 
public:
 /*...*/

private:
 Transform mTransform;

Also, component can have some handy functions about itself if needed.

Entity is a container of components and responsible of its creation/deletion of the component.

class Entity 
public:
 template <typename T, typename ...Args>
 bool attach(Args ... args);
 template <typename T>
 bool detach();
 template <typename T>
 T* get();
 /*...*/

private:
 ComponentTypeBit mComponentBit;
 std::unordered_map<ComponentTypeBit, ComponentIsh> mComponentMap;

System manipulates component(s) of an entity. A system can be interested in one or more component types. Entity can be registered to a system. If an entity has all components that required by a system, then system stores the pointer of entity.

template<typename ... Args>
class System 
public:
 /*...*/
 void registerEntity(Entity& entity);
 void deregisterEntity(Entity& entity);
 const std::vector<Entity*>& getEntities() const;
 /*...*/
private:
 ComponentTypeBit mComponentBit;
 std::vector<Entity*> mEntities;


class HierarchySystem : public System<HierarchyComponent, TransformComponent> 
 /*If a entity has HierarchyComponent and TransformComponent,
 address of the entity adds to mEntities*/

The question is, well, not just about render class itself.

If I want to render an arbitary (static)mesh, I need view matrix and projection matrix from camera. My confusion started from here.

At first glance, I though mesh renderer can be defined like this:

class MeshRenderSystem : public System<TransformComponent, MeshComponent, MaterialComponent>
/*currently, MaterialComponent holds reference to fragment shader*/

So I can set model matrix uniform and vertex attributes, material uniforms.
But where should I put view and projection matrix? What about draw call?

Idea 1: class Scene that holds list of entities and camera(s).

Possible issue: The camera is not an entity. That means I need something like CameraTargetComponent. But to update that component, a system should reference to Scene

Idea 2: CameraComponent that represents the camera. Thus camera can have parent or children by HierarchyComponent.

Possible issue: If camera is an entity, where should I store view and projection matrix to render(because my systems don't have event queue or vice versa)? Do I need something like Scene again?

Idea 3: SceneManager that has SystemProvider and EntityProvider. And If an entity created by EntityProvider and registered to current scene of SceneManager then also registered to to system. SceneManager hold camera(s) and renderers.