This is an ECS game engine written in C++20 with no external ECS library. Components are stored in sparse sets, with one densely packed array per component type. Iteration is cache-friendly, and adding, removing or looking up a component is O(1). Component types are assigned IDs at compile time through templates.
Queries are done using variadic templates and Iterators, for example reg.query<Transform, Mesh>(). They return an Iterator you can use in a range-based for-loop. A query iterates the smallest of the requested component pools and checks membership in the others, so its cost scales with the rarest component rather than the total entity count. When Entities/Components are "removed", deletion is deferred. Anything removed mid-frame is marked "dead", skipped by the iterator, and removed in a single flush() at the end of the frame. This makes it safe to destroy entities while iterating.
Entities are generational handles. Each entity index carries a generation counter, so a stale handle to a destroyed entity is detected instead of silently aliasing whatever reuses its slot.
Logic lives in systems: classes with start(), update() and onDestroy() hooks. Systems like camera control and rendering are all implemented as systems that read plain-data components.
Example psuedocode:
//Component: Camera
struct Camera {
float fov = 45.0f;
vec3 cameraDirection;
vec3 cameraPos;
}
//System: RenderSystem
class RenderSystem : public ISystem{
void start() override {
Camera cameraComp{...};
EntityHandle handle = ecs.newEntity();
ecs.addComponent(handle, cameraComp);
}
void update() override {
Query q = ecs.query<Camera>();
for (auto [entityHandle, camera] : q) {
glm::mat4 projection;
projection = glm::perspective(camera.fov, camera.cameraDirection, ...);
glUseProgram(myShader);
...
}
}
}I am planning to turn this project into a Minecraft clone as it's something I'm familiar with and offers me with a sandbox-y environment to explore programming ideas such as more advanced lighting and shader effects. I am currently sticking to OpenGL as it allows me to focus on concepts without the deep plumbing requirements of Vulkan.
The ECS data structures / logic were written without any AI-generated code. I aim to responsibly use AI mainly as a learning tool as game engines and graphics programming necessitate independent thinking / deep understanding of underlying systems and hardware.