title: How Do I Use an HTML5 Canvas as a WebGL Texture
body: <p>I want to:</p>
  
  <ol>
  <li>Set Uniform values for case i. </li>
  <li>Render compute shader for case i to an HTML5 <code>&lt;canvas&gt;</code> tag.</li>
  <li>Use the <code>&lt;canvas&gt;</code> contents (case i render output) as a texture in the next render pass.</li>
  <li>Repeat for all cases.</li>
  <li>Extract answers into JS from color data.</li>
  </ol>
  
  <p>I'm trying to make a compute shader and need to carry a value per pixel (fragment) on each render pass. A simple example would be incrementing the blue value of a pixel on each render call.</p>
  
  <p>I.e. </p>
  
  <pre><code>pass 1: b=1
  pass 2: b=2
  pass 2: b=3
  etc.
  </code></pre>
  
  <ol>
  <li><p><strong>Is this kind of a shader loop even possible?</strong> </p></li>
  <li><p><strong>Is there a better way to keep a'carry' texture in video memory for multipass processing (where uniform values must change between passes, unlike standard in-shader multipass processing)?</strong></p></li>
  </ol>