title: Compatibility issues on GLSL fragment shaders
body: <p>I have found a few times differences between GPUs handling fragment shaders. One example was doing <code>pow(x)</code> where <code>x</code> is negative. One GPU handled it well while the other one failed.</p>
  
  <p>Another situation was where I rewrote <code>if()</code> statements with <code>step()</code> statement and shader worked well. I blamed this to branching limit or something.</p>
  
  <p>Now I am in situation where my fragment shader works on some GPUs and on some don't. I have tried to search for GPU/shader limits and similar information but found nothing.</p>
  
  <p>The very current test which works everywhere I tried except on my GTX 780 is <a href="https://www.shadertoy.com/view/XssXDH" rel="nofollow">here online(Shadertoy)</a></p>
  
  <p><strong>I am asking for any directions or a link to shader limitations and most common issues in compatibility.</strong></p>