在 Java 中将角度归一化为 +/- π 弧度的标准方法
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原文地址: http://stackoverflow.com/questions/24234609/
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Standard way to normalize an angle to +/- π radians in Java
提问by David Moles
Is there a library function or a well-known quick efficient way in Java to normalize an angle to +/- π — e.g. when adding two angles?
Java 中是否有库函数或众所周知的快速有效的方法来将角度归一化为 +/- π——例如，在添加两个角度时？
What I've got now (based on this answer) is basically the code below...
我现在得到的（基于这个答案）基本上是下面的代码......
private static final double TWO_PI = 2 * Math.PI;
double normalize(double theta) {
double normalized = theta % TWO_PI;
normalized = (normalized + TWO_PI) % TWO_PI;
return normalized <= Math.PI ? normalized : normalized - TWO_PI;
}
...but it seems a little complicated and performance-wise I'm not excited about the modulo operator. (Note that I can't guarantee thetaisn't some relatively large number, so I don't think there's a pure addition/subtraction solution without looping. I don't actually know how a hand-rolled loop is likely to compare to %.)
...但它似乎有点复杂和性能方面我对模运算符并不感到兴奋。（请注意，我不能保证theta不是某个相对较大的数字，因此我认为没有没有循环的纯加法/减法解决方案。我实际上不知道手动循环与%. )
Is there a well-tested optimized library function I can use, or a better algorithm, or is this as good as it gets?
是否有我可以使用的经过充分测试的优化库函数，或者更好的算法，或者它是否已经足够好？
采纳答案by CupawnTae
Apache commons has one:
Apache Commons 有一个：
normalize an angle between -π and +π
a = MathUtils.normalizeAngle(a, 0.0);
标准化 -π 和 +π 之间的角度
a = MathUtils.normalizeAngle(a, 0.0);
And looking at the source code, you could reproduce it with this (they use their own FastMath.floorbut in case you want to do it without an external library):
查看源代码，您可以使用它来重现它（他们使用自己的代码，FastMath.floor但如果您想在没有外部库的情况下执行此操作）：
theta - TWO_PI * Math.floor((theta + Math.PI) / TWO_PI)
来源在这里：https: //github.com/apache/commons-math/blob/53ec46ba272e23c0c96ada42f26f4e70e96f3115/src/main/java/org/apache/commons/math4/util/MathUtils.java#L107
Note for readers from the future: this method has just (June 2017) been removedfrom the latest commons-math 4.x codebase. If you're using a version after this, you'll want to use commons-numbersinstead (once it's released) - currently:
未来读者请注意：此方法刚刚（2017 年 6 月）从最新的 commons-math 4.x 代码库中删除。如果您在此之后使用一个版本，您将需要使用commons-numbers代替（一旦发布） - 目前：
a = PlaneAngleRadians.normalizeBetweenMinusPiAndPi(a);
or
或者
a = PlaneAngleRadians.normalize(a, 0.0);
回答by cohadar
There is only one 100% foolproof way:
只有一种 100% 万无一失的方法：
public static double normalizeAngle(double angle) {
return Math.atan2(Math.sin(angle), Math.cos(angle));
}
Everything else is people trying to be too smart and failing.
其他一切都是人们试图变得过于聪明和失败。
