问题描述
如果我使用坐标数组定义了某些形状,例如
If I have some shapes defined using arrays of coordinates e.g.
[[-30, -30], [-30, 30], [30, 30], [30, -30]]
和使用:
[[0,1],[0,3],[1,2],[2,3]]
做一个正方形。
如何我以编程方式告诉形状在中心旋转*相对于javascript中0-> 359的角度吗?
How do I programmatically tell the shape to rotate *at the center against an angle of 0->359 in javascript?
*或者更好的是,有没有一个函数允许我选择旋转中心?
*Or better yet, is there a function which allows me to choose the center of rotation?
**
目前,我已经设法使用:
**Currently, I've managed to get the shape to circle the canvas using :
var x_rotate = Math.sin(angle * Math.PI /180);
var y_rotate = Math.cos(angle * Math.PI /180);
// for each coordinate
//add x_rotate and y_rotate if coordinate > 0 or subtract if coordinate < 0
推荐答案
在这里,旋转点 x,y
围绕点 centerx,centery
围绕 degrees
度。返回浮点值,如果需要,则取整。
Here you go, rotates point x, y
around point centerx, centery
by degrees
degrees. Returns floating values, round if you need to.
要旋转形状,请旋转所有点。
To rotate a shape, rotate all the points. Calculate the center if you need to, this does not do it.
Desmos link with x
as a
, y
as b
, centerx
as p
, centery
as q
, and degrees
as s
function rotatePoint(x, y, centerx, centery, degrees) {
var newx = (x - centerx) * Math.cos(degrees * Math.PI / 180) - (y - centery) * Math.sin(degrees * math.PI / 180) + centerx;
var newy = (x - centerx) * Math.sin(degrees * Math.PI / 180) + (y - centery) * Math.cos(degrees * math.PI / 180) + centery;
return [newx, newy];
}
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