如何旋转坐标系？ [英] How to rotate coordinate system?

问题描述

如果我绕原点旋转，我正在尝试查找坐标的新值。

I am trying to find the new value of a coordinate if I rotate around the origin.

例如，说我有一点（1,1）。
如果我将坐标轴绕原点旋转45度，则变换后的坐标将为（0,1.414）

For example, say I have the point (1,1). If I rotate the coordinate axis 45 degrees around the origin, the transformed coordinate would be (0,1.414)

有没有一种方法可以在cocos2d，还是在objective-c中？
甚至解释数学的答案也将有所帮助。

Is there a way to do this efficiently in cocos2d, or in objective-c ? Even answers explaining the math to do this would be helpful.

推荐答案

请参见本页：
< a href = http://www.siggraph.org/education/materials/HyperGraph/modeling/mod_tran/2drota.htm rel = noreferrer> http://www.siggraph.org/education/materials/HyperGraph/模拟/mod_tran/2drota.htm

这是公式：

x'= x cos f-y sin f

x' = x cos f - y sin f

y'= y cos f + x sin f

y' = y cos f + x sin f

记住罪和cos采用弧度，因此您必须这样做：

Remember that sin and cos takes radians, so you have to do like this:

double x,y;
double newX,newY;
double angle;

//Test values:
x=1;
y=1;
angle = 45;

double rad = angle*M_PI/180;

newX = x * cos(rad) - y * sin(rad);
newY = y * cos(rad) + x * sin(rad);

我没有测试，所以可能会有错别字...;）

I didn't test this, so there might be typos... ;)

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