Hi I come from the Flappy Bird Course using SFML from udemy. This its not  a problem but an explanation I required here.

On the main Game.cpp where everything its handle we have this code:

void Game::Run()
	{
		float newTime, frameTime, interpolation; //frameTime
		float currentTime = mClock.getElapsedTime().asSeconds();
		float accumulator = 0.0f;

		while (mData->window.isOpen())
		{
			//1.handle events and changes
			mData->machine.ProcessStateChanges();

			newTime = mClock.getElapsedTime().asSeconds();

			frameTime = newTime - currentTime; //The time that took a frame to be executed

			if (frameTime > 0.25f)
			{
				frameTime = 0.25f;
			}

			currentTime = newTime;
			accumulator += frameTime;

			while (accumulator >= dt)
			{
				mData->machine.GetActiveState()->HandleInput();
				mData->machine.GetActiveState()->Update(dt);

				accumulator -= dt;
			}

			interpolation = accumulator / dt;
			mData->machine.GetActiveState()->Draw(interpolation);
		}
	}

I would like some detail explanation on the frame mathematics here.

I do understand that our while()  here its executed once every frame or at least thats what we want to achieve here.

So we calculate the time between frames as the difference of time between the previous call to our while() and the next one the while() its call.

Once the frameTime has been calculated, we check if frameTime > 0.25 and if so its set to 0.25...¿why its this done? I guess its to set a limit but no clue.

Then theres the accumulator and the while (accumulator > dt). dt its 1/60 which its the time that takes 1 frame to be executed at 60 fps.

I dont understand this part too well. An example to understand it would be great.

Thank you