title: How to get plane-vertices by a point and normal
body: <p>I'm having a point <code>p</code> and a normal <code>n</code> (in 3d space).
  I want to calculate 4 vertex-points which are lying on the plane which is perpendicular to the normal and lies on the point <code>p</code>.</p>
  
  <p>The vertices should form a rectangle and <code>p</code> should be the center of this rectangle.</p>
  
  <p><img src="https://i.stack.imgur.com/YyGa3.png" alt="enter image description here"></p>