循环移动背景objective-C

发布于 2024-12-07 08:24:21 字数 471 浏览 0 评论 0原文

我正在测试一个背景循环动画，其中尺寸均为 1024x768 像素的图像，向左移动，离开屏幕，然后跳回另一侧，然后重复。

我能够通过为两个背景图像移动创建恒定的速度（成功）来做到这一点，然后我尝试使用以下代码使其跳跃，但出现了一个问题：

    if((background.center.x) < -511){
        background.center = CGPointMake(1536, background.center.y);
    }

    if((background2.center.x) < -511){
        background2.center = CGPointMake(1536, background2.center.y);
    }

不知怎的，这并没有按照我预期的方式工作。它每次都会留下几个像素的间隙，我很困惑为什么。有谁知道是什么原因导致这种情况发生以及如何解决？谢谢！

原文

I am testing a background-loop animation where there will be to images both 1024x768 pixels in dimension, move leftwards, go offscreen, then jump back to the other side, and repeat.

I was able to do this by creating a constant speed for both background image to move (successful), and then I tried the following code to make it jump, but there was a problem:

    if((background.center.x) < -511){
        background.center = CGPointMake(1536, background.center.y);
    }

    if((background2.center.x) < -511){
        background2.center = CGPointMake(1536, background2.center.y);
    }

Somehow this is not working the way I expected. It leaves a few pixels of gap every time, and I am confused why. Does anyone know what's causing this to happen and how to fix it? Thanks!

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时光清浅 2024-12-14 08:24:21

您似乎忘记考虑移动的距离。由于您移动到较远的位置，可能会触发大于表达式。我猜你的运动大于 1 像素/帧。

我不确定什么样的价值观正在滋养你的运动，但我认为考虑到你的运动，你应该做一些事情......

 if ((background.center.x) < -511){
    CGFloat dist = background.center.x + 512;
    background.center = CGPointMake(1536+dist, background.center.y);
 }

 if ((background2.center.x) < -511){
    CGFloat dist = background2.center.x + 512;
    background2.center = CGPointMake(1536+dist, background2.center.y);
 }

It seems like you have forgotten to take into account the distance moved. The greater than expression might have been triggered because you moved to far. I guess your movement is larger than 1 pixel/frame.

I am not sure what kind of values that are feeding your movement but I think to take into account the movement you should do something like...

 if ((background.center.x) < -511){
    CGFloat dist = background.center.x + 512;
    background.center = CGPointMake(1536+dist, background.center.y);
 }

 if ((background2.center.x) < -511){
    CGFloat dist = background2.center.x + 512;
    background2.center = CGPointMake(1536+dist, background2.center.y);
 }

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夜光 2024-12-14 08:24:21

我不会让两个图像（某种程度上）独立移动，而是跟踪一个 backgroundPosition 变量，然后不断更新两个图像相对于该位置的位置。这应该使一切保持整洁：

CGFloat const backgroundWidth = 1024;
CGFloat const backgroundSpeed = 2;

- (void)animateBackground {
    backgroundPosition -= backgroundSpeed;
    if (backgroundPosition < 0) {
        backgroundPosition += backgroundWidth;
    }
    background1.center.x = backgroundPosition - backgroundWidth/2;
    background2.center.x = backgroundPosition + backgroundWidth/2;
}

Rather than have the two images move (sort of) independently, I would keep track of a single backgroundPosition variable and then constantly update the position of both images relative to that one position. This should keep everything nice and tidy:

CGFloat const backgroundWidth = 1024;
CGFloat const backgroundSpeed = 2;

- (void)animateBackground {
    backgroundPosition -= backgroundSpeed;
    if (backgroundPosition < 0) {
        backgroundPosition += backgroundWidth;
    }
    background1.center.x = backgroundPosition - backgroundWidth/2;
    background2.center.x = backgroundPosition + backgroundWidth/2;
}

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