正文

方便计算，这里让\(\omega_0=1\)

便于理解，\(x=\theta,y=\dot{x}=\omega\)

于是

\(\frac{dx}{dt}=y\\\frac{dy}{dt}=-\sin(x)\)

Vector field里面写这个

// p.x and p.y are current coordinates
// v.x and v.y is a velocity at point p
vec2 get_velocity(vec2 p) {
  vec2 v = vec2(0., 0.);

  // change this to get a new vector field
  v.x = p.y;
  v.y =sin(p.x);
  return v;
}

录了个视频

<iframe src="//player.bilibili.com/player.html?aid=713586465&amp;cid=280516393&amp;page=1" scrolling="no" border="0" frameborder="no" framespacing="0" allowfullscreen="true" width="95%" height="450">
</iframe>

参考

https://wenku.baidu.com/view/e0f43d3e4973f242336c1eb91a37f111f1850dce.html 单摆运动相图

作图网站url，?query=也写进去了

https://www.cnblogs.com/artoriax/p/10364915.html 博客内插入bilibili视频

one minor hiccup

v.y =sin(p.x);
这里正负号打反了，将就着看吧。相位差了\(\pi\)

单摆相图绘制

原文：https://www.cnblogs.com/yhm138/p/14257879.html