从计算的角度上圆的周长点在C＃中？ [英] Calculating point on a circle's circumference from angle in C#?

问题描述

我想，这是一个简单的问题，但我发现了我目前的code一些奇怪的结果，我没有数学背景，充分理解为什么。我的目标很简单，正如标题说：我只是想找到从中心点一定距离和角度的点

I imagine that this is a simple question, but I'm getting some strange results with my current code and I don't have the math background to fully understand why. My goal is simple, as stated in the title: I just want to find the point at some distance and angle from a center point.

我目前的code：

Point centerPoint = new Point ( 0, 0 );
Point result      = new Point ( 0, 0 );
double angle      = 0.5; //between 0 and 2 * PI, angle is in radians
int distance      = 1000;

result.Y = centerPoint.Y + (int)Math.Round( distance * Math.Sin( angle ) );
result.X = centerPoint.X + (int)Math.Round( distance * Math.Cos( angle ) );

在一般情况下，这似乎相当合理工作，但我得到在各个点的问题，最值得注意的是，当角对应点在负x和y轴。显然，我做错了什么吗？ - 那是什么想法

In general, this seems to work fairly reasonably, but I get problems at various spots, most notably when the angle corresponds to points in the negative x and y axis. Clearly I'm doing something wrong -- thoughts on what that is?

更新：这是我的错，这code正常工作 - 即不工作实际上是少数异常值由于是如何被计算1.5PI角度的错误。我想我已经检查了还不错，但显然没有。感谢大家的时间，希望工作code以上将证明是有益的给别人。

UPDATE: This was my mistake, this code works fine -- the few outliers that were not working were actually due to a bug in how the angle for 1.5PI was being calculated. I thought I had checked that well enough, but evidently had not. Thanks to everyone for their time, hopefully the working code above will prove helpful to someone else.

推荐答案

您忘了加中心点：

result.Y = (int)Math.Round( centerPoint.Y + distance * Math.Sin( angle ) );
result.X = (int)Math.Round( centerPoint.X + distance * Math.Cos( angle ) );

剩下的应该没问题。（是你得到什么奇怪的结果？你能给出一个确切的输入？）

The rest should be ok... (what strange results were you getting? Can you give an exact input?)

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