title: How to determine the 3D boundaries of camera field of view in three.js
body: <p>I have a three.js scene and would like to know the 3D boundaries of the viewport.</p>
  
  <p>For instance, let's say I have a canvas that is 500px wide and 1000px tall. My camera is looking at position <code>{ 0, 0, 0 }</code> and is at position <code>{ 0, 0, 100 }</code>;</p>
  
  <p>My camera will never move.</p>
  
  <p>Let's say I have an object located at <code>{ 0, 0, 0 }</code>. I need to be able to move that object to various points within the viewable area (within the camera field of view). How can I calculate, say, the upper/left hand corner of the camera's field of view? Also, how could I calculate 20% in from the left and 10% down from the top of the camera's field of view?</p>
  
  <p>Here is my camera object:</p>
  
  <pre><code>{
      "object": {
          "uuid": "E26C5F88-CD17-45F8-A492-F3DD704949BF",
          "type": "PerspectiveCamera",
          "matrix": [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 100, 1],
          "zoom": 1,
          "fov": 50,
          "aspect": 0.625,
          "near": 0.1,
          "far": 1000
      }
  }
  </code></pre>