2D精灵旋转 [英] 2D Sprite Rotation

问题描述

你好！

我需要旋转2D精灵的帮助.我想要做的是不断平滑旋转精灵，但是旋转速度会不时变化.它加速和减速.

I need help rotating 2D sprites. What I’m trying to do is smooth rotate a sprite constantly but the speed of the rotation varies from time to time. It accelerates and decelerates.

我使用浮动速度乘以(float)gameTime.ElapsedGameTime.TotalMillisecods来增加spriteBatch.Draw方法中的旋转.我正在使用弧度，它将继续无限旋转，没有问题，但是角度不断增加，我 在变量变得太大并崩溃之前，不知道它将旋转多长时间.

I use a float Speed multiplied by (float)gameTime.ElapsedGameTime.TotalMillisecods to add to the rotation in the spriteBatch.Draw method. I am using radians and it will continue to rotate indefinitely without problems but the angle keeps adding up and I don’t know for how long it will rotate until the variable becomes too big and crashes.

我还知道选项之一是在每次旋转时添加一个IF，然后查看角度是否为特定数值，然后将变量重置为再次从cero开始，但是由于sprite旋转的速度不同，因此重置为cero会导致精灵 跳起来，我需要一直保持平稳旋转.

I also know that one of the options is to add an IF at every rotation and see if the angle is at a specific number then resetting the variable to start from cero again but because the sprite rotates at different speeds, resetting to cero will cause the sprite to "jump" and I need smooth rotation all the time.

谢谢…

推荐答案

这是一种使用变量计算每帧旋转的方法:

This is one way you can calculate your rotation each frame using your variables:

rot =((int)(速度*(float)gameTime.TotalGameTime.TotalMilliseconds)％360);

rot = ((int)(speed * (float)gameTime.TotalGameTime.TotalMilliseconds) % 360);

这将始终为您提供0到359的值，该值可以平稳过渡(如果希望它以其他方式旋转，请在前面加上负号)，然后可以将其与以下项一起使用:MathHelper.ToRadians(rot)

This will always give you a 0 to 359 value which transitions smoothly (put a negative sign in front if you want it to rotate the other way), which you can then use with: MathHelper.ToRadians(rot)

此处的键是'％'运算符.它需要一个int值，其功能类似于除法运算，只不过它返回余数.它将允许您使用任何IF语句来解决问题.另外，我以0.03f的速度为例.

The key here is the '%' operator. It requires an int value and functions like a division calculation, except it returns the remainder instead. It will allow you to get around using any IF statements. Also, I used a speed of 0.03f as an example.

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