了解游戏循环中的滴答插值

Question

抱歉，我只是在游戏循环中研究状态管理，我需要一些帮助来了解作者采用这种方式进行操作的原因。

void Game::run() {
    float newTime, frameTime, interpolation;
    float accumulator = 0.f;
    float currentTime = gameClock.getElapsedTime().asSeconds();

    while(data->renderWindow.isOpen()){
        data->stateManager.makeChanges();
        newTime = gameClock.getElapsedTime().asSeconds();
        frameTime = newTime - currentTime;
        if(frameTime > 0.2f)
            frameTime = 0.2f;       //why this if?
        currentTime = newTime;
        accumulator += frameTime;     //why don't he just make actions every dt time?
        while(accumulator >= dt){
            data->stateManager.getActiveState()->handleInput();
            data->stateManager.getActiveState()->update(dt);
            accumulator -= dt;
        }
        interpolation = accumulator/dt;
        data->stateManager.getActiveState()->draw(interpolation);    //really can't understand this :(
    }
}

我对我不了解的地方发表了评论。