2D欧几里德矢量旋转 [英] 2D Euclidean vector rotations
问题描述
我有一个坐标为(0,1)
的欧氏向量 a
。
我想围绕原点将旋转90度(顺时针):
(0,0)
I have a euclidean vector a
sitting at the coordinates (0, 1)
.
I want to rotate a
by 90 degrees (clockwise) around the origin: (0, 0)
.
如果我正确理解这应该如何工作,旋转后的结果(x,y)坐标应该(1, 0)
。
如果我将它旋转45度(仍然顺时针),我会预期结果坐标为(0.707,0.707)
。
If I have a proper understanding of how this should work, the resultant (x, y) coordinates after the rotation should be (1, 0)
.
If I were to rotate it by 45 degrees (still clockwise) instead, I would have expected the resultant coordinates to be (0.707, 0.707)
.
theta = deg2rad(angle);
cs = cos(theta);
sn = sin(theta);
x = x * cs - y * sn;
y = x * sn + y * cs;
使用上述代码,使用 angle
值为90.0度,则结果坐标为:( - 1,1)
。
我很害怕。
以下链接中的示例代表了上面显示的相同公式?
Using the above code, with an angle
value of 90.0 degrees, the resultant coordinates are: (-1, 1)
.
And I am so damn confused.
The examples seen in the following links represent the same formula shown above surely?
我做错了什么?
或者我误解了一个向量是如何旋转的:
What have I done wrong? Or have I misunderstood how a vector is to be rotated?
推荐答案
你应该从函数中删除vars:
you should remove the vars from the function:
x = x * cs - y * sn; // now x is something different than original vector x
y = x * sn + y * cs;
创建新坐标,避免在到达第二行之前计算x:
create new coordinates becomes, to avoid calculation of x before it reaches the second line:
px = x * cs - y * sn;
py = x * sn + y * cs;
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