title: How can i get previous frame data in glsl?
body: <p>There is a site, <a href="http://www.shadertoy.com" rel="nofollow noreferrer">shadertoy.com</a> where i can easily test glsl code. Now I would like to play with my webcam. One my required step is to lowpass renderred image between frames: </p>
  
  <pre><code>void mainImage( out vec4 fragColor, in vec2 fragCoord )
  {
      vec2 uv = fragCoord.xy / iResolution.xy;
      fragColor.rgb = prevColor.rgb*0.9 + texture(iChannel0, uv).rgb*0.1;
  }
  </code></pre>
  
  <p>New webcam frame is located in <code>iChannel0</code> texture;  but <code>prevColor</code> - I can*t get. Where can I get previously rendered frame? Or how can I store rendered <code>fragColor.rgb</code> data, to make it "survive" between passes?</p>