title: How can I draw a fullscreen background image in WebGL like sketchfab?
body: <p>I know how to draw models, but I don't know how to draw a fullscreen background image.</p>
  
  <p>I think I should draw it at the zfar of the camera. But I have no idea how to calculate its size...</p>
  
  <p>In sketchfab, it seems the background image can implement the css property<code>background-size: cover</code>. And I notice sketchfab do not implement it by css.</p>
  
  <p>I really want to know how to implement this!</p>
  
  <p><a href="https://i.stack.imgur.com/ujFK3.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ujFK3.png" alt="enter image description here"></a></p>