我正在尝试学习一些基本的向量数学,但我似乎无法让这种旋转点的方法发挥作用。旋转矢量的大小正在按比例放大,我不知道 Angular 是怎么回事。
这是相关的函数。我正在使用 javascript/HTML Canvas 。
function rotate(point, center, angle) {
var theta = (Math.PI / 180) * angle,
cX = center.pos.x,
cY = center.pos.y,
pX = point.pos.x,
pY = point.pos.y,
pCos = Math.cos(theta),
pSin = Math.sin(theta),
x = pX - cX,
y = pY - cY;
x = (x * pCos - y * pSin) + cX;
y = (x * pSin + y * pCos) + cY;
return {x: Math.floor(x), y: Math.floor(y)};
}
最佳答案
该函数几乎是正确的,但您只是使用修改后的 x 值来计算 y
function rotate(point, center, angle) {
var theta = (Math.PI / 180) * angle,
cX = center.pos.x,
cY = center.pos.y,
pX = point.pos.x,
pY = point.pos.y,
pCos = Math.cos(theta),
pSin = Math.sin(theta),
x = pX - cX,
y = pY - cY;
/* You had
x = (x * pCos - y * pSin) + cX; // you change x on this line
y = (x * pSin + y * pCos) + cY; /// then used the modified x to get y
*/
// this will fix the problem
var xx = (x * pCos - y * pSin) + cX;
var yy = (x * pSin + y * pCos) + cY;
return {x: Math.floor(xx), y: Math.floor(yy)};
}
关于javascript - 旋转 HTML Canvas 中的点,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38568104/