title: HLSL How can one pass data between shaders / read existing colour value?
body: <p>I have 2 HLSL ps2.0 shaders. Simplified, they are:</p>
  
  <p>Shader 1<br> </p>
  
  <ul>
  <li>Reads texture</li>
  <li>Outputs colour value based on this texture</li>
  </ul>
  
  <p>Shader 2<br></p>
  
  <ul>
  <li><b>Problem: Need to read in the colour from Shader 1</b></li>
  <li>Outputs the final colour which is a function of the input colour</li>
  </ul>
  
  <p>(They need to be different shaders as I've reached the maximum vertex-shader outputs for 1 shader)</p>
  
  <hr>
  
  <p>My problem is I cannot work out how Shader 2 can access the existing fragment/pixel colour. <br></p>
  
  <p>Knowing how to do any of these things with HLSL would solve my problem;</p>
  
  <ul>
  <li>Read existing pixel colour (I don't think this is possible)</li>
  <li>Pass result of Shader 1 to Shader 2 as a float4</li>
  <li>Render result of Shader 1 as a texture in memory, and have Shader 2 read that in</li>
  </ul>