如何并行使用requestAnimationFrame和setTimeout来制作更好的游戏循环？

Question

我的目标是创建一个有效的游戏循环，该循环requestAnimationFrame用于更新显示画布和setTimeout更新游戏逻辑。我的问题是我应该将所有绘图操作放到requestAnimationFrame循环中还是仅将更新HTML画布的主绘图操作放到循环中？

我所说的“所有绘制操作”是所有缓冲。例如，我将所有的精灵绘制到缓冲区，然后将缓冲区绘制到主画布。一方面，如果我将所有缓冲放入其中，则requestAnimationFrame不会在每次逻辑更新时都浪费cpu绘图，另一方面，绘图会占用大量cpu并可能导致requestAniomationFrame等待所有这些操作完成...将逻辑更新与绘图分开的目的是requestAnimationFrame不会因非绘图处理而陷入困境。

有没有人对使用这种创建游戏循环的方法有任何经验？而且不要说“只把它全部放进去requestAnimationFrame”，因为这会减慢渲染速度。我坚信将逻辑与绘图分开是必经之路。这是我正在谈论的示例：

/* The drawing loop. */
function render(time_stamp_){//First parameter of RAF callback is timestamp.
    window.requestAnimationFrame(render);

    /* Draw all my sprites in the render function? */
    /* Or should I move this to the logic loop? */
    for (var i=sprites.length-1;i>-1;i--){
        sprites[i].drawTo(buffer);
    }

    /* Update the on screen canvas. */
    display.drawImage(buffer.canvas,0,0,100,100,0,0,100,100);
}

/* The logic loop. */
function update(){
    window.setTimeout(update,20);

    /* Update all my sprites. */
    for (var i=sprites.length-1;i>-1;i--){
        sprites[i].update();
    }
}

谢谢！

编辑：

我决定与网络工作者一起将游戏逻辑与图形完全分离，据我所知，图形必须在DOM加载的主脚本中进行。

Answer 1

因此，我从未找到分离逻辑和绘图的好方法，因为 JavaScript 使用单线程。无论我做什么，绘图函数的执行都可能会妨碍逻辑，反之亦然。我所做的就是找到一种尽可能最及时地执行它们的方法，同时确保不断更新逻辑并使用 requestAnimation Frame 优化绘图。该系统设置为插入动画，以在设备速度太慢而无法以所需帧速率绘制时弥补跳帧。无论如何，这是我的代码。

var engine = {
        /* FUNCTIONS. */
        /* Starts the engine. */
        /* interval_ is the number of milliseconds to wait between updating the logic. */
        start : function(interval_) {
            /* The accumulated_time is how much time has passed between the last logic update and the most recent call to render. */
            var accumulated_time = interval_;
            /* The current time is the current time of the most recent call to render. */
            var current_time = undefined;
            /* The amount of time between the second most recent call to render and the most recent call to render. */
            var elapsed_time = undefined;
            /* You need a reference to this in order to keep track of timeout and requestAnimationFrame ids inside the loop. */
            var handle = this;
            /* The last time render was called, as in the time that the second most recent call to render was made. */
            var last_time = Date.now();

            /* Here are the functions to be looped. */
            /* They loop by setting up callbacks to themselves inside their own execution, thus creating a string of endless callbacks unless intentionally stopped. */
            /* Each function is defined and called immediately using those fancy parenthesis. This keeps the functions totally private. Any scope above them won't know they exist! */
            /* You want to call the logic function first so the drawing function will have something to work with. */
            (function logic() {
                /* Set up the next callback to logic to perpetuate the loop! */
                handle.timeout = window.setTimeout(logic, interval_);

                /* This is all pretty much just used to add onto the accumulated time since the last update. */
                current_time = Date.now();
                /* Really, I don't even need an elapsed time variable. I could just add the computation right onto accumulated time and save some allocation. */
                elapsed_time = current_time - last_time;
                last_time = current_time;

                accumulated_time += elapsed_time;

                /* Now you want to update once for every time interval_ can fit into accumulated_time. */
                while (accumulated_time >= interval_) {
                    /* Update the logic!!!!!!!!!!!!!!!! */
                    red_square.update();

                    accumulated_time -= interval_;
                }
            })();

            /* The reason for keeping the logic and drawing loops separate even though they're executing in the same thread asynchronously is because of the nature of timer based updates in an asynchronously updating environment. */
            /* You don't want to waste any time when it comes to updating; any "naps" taken by the processor should be at the very end of a cycle after everything has already been processed. */
            /* So, say your logic is wrapped in your RAF loop: it's only going to run whenever RAF says it's ready to draw. */
            /* If you want your logic to run as consistently as possible on a set interval, it's best to keep it separate, because even if it has to wait for the RAF or input events to be processed, it still might naturally happen before or after those events, and we don't want to force it to occur at an earlier or later time if we don't have to. */
            /* Ultimately, keeping these separate will allow them to execute in a more efficient manner rather than waiting when they don't have to. */
            /* And since logic is way faster to update than drawing, drawing won't have to wait that long for updates to finish, should they happen before RAF. */

            /* time_stamp_ is an argument accepted by the callback function of RAF. It records a high resolution time stamp of when the function was first executed. */
            (function render(time_stamp_) {
                /* Set up the next callback to RAF to perpetuate the loop! */
                handle.animation_frame = window.requestAnimationFrame(render);

                /* You don't want to render if your accumulated time is greater than interval_. */
                /* This is dropping a frame when your refresh rate is faster than your logic can update. */
                /* But it's dropped for a good reason. If interval > accumulated_time, then no new updates have occurred recently, so you'd just be redrawing the same old scene, anyway. */
                if (accumulated_time < interval_) {
                    buffer.clearRect(0, 0, buffer.canvas.width, buffer.canvas.height);

                    /* accumulated_time/interval_ is the time step. */
                    /* It should always be less than 1. */
                    red_square.draw(accumulated_time / interval_);

                    html.output.innerHTML = "Number of warps: " + red_square.number_of_warps;

                    /* Always do this last. */
                    /* This updates the actual display canvas. */
                    display.clearRect(0, 0, display.canvas.width, display.canvas.height);
                    display.drawImage(buffer.canvas, 0, 0, buffer.canvas.width, buffer.canvas.height, 0, 0, display.canvas.width, display.canvas.height);
                }
            })();
        },
        /* Stops the engine by killing the timeout and the RAF. */
        stop : function() {
            window.cancelAnimationFrame(this.animation_frame);
            window.clearTimeout(this.timeout);
            this.animation_frame = this.timeout = undefined;
        },
        /* VARIABLES. */
        animation_frame : undefined,
        timeout : undefined
    };

这是直接从我的一个项目中删除的，因此其中有一些变量是在代码中的其他地方定义的。red_square 是这些变量之一。如果您想查看完整的示例，请查看我的 github 页面！userpoth.github.io另外，顺便说一句，我尝试使用网络工作人员来分离逻辑，但这是一次悲惨的失败。当您需要执行大量数学运算并且需要在线程之间传递很少的对象时，Web Workers 非常有用，但它们无法进行绘图，并且在大数据传输方面速度很慢，至少在游戏逻辑的上下文中是这样。