title: How can i make gradient sphere on glsl?
body: <p>I'm just a noob to GLSL and don't know how to do this in GLSL.<br>
  What I trying to do is making alpha value to 1 on center of sphere and drop gradually on outer.</p>
  
  <p>So I made a prototype using Blender node editor and that's how I did.
  <a href="https://i.stack.imgur.com/uV8Fv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uV8Fv.png" alt="Sphere gradient"></a></p>
  
  <p>Now I am trying to do this in glsl.<br>
  Maybe i can use gl_Normal to replace "normal on Geometry" on Blender.<br>
  (Though it's removed after version 140, my final goal is just "make" it, so ignore that.)<br>
  And there are also dot function to calculate "dot product on vector math" on glsl.  </p>
  
  <p>Now i need is "View vector of camera data" and "ColorRamp".<br>
  I think "ColorRamp" can be done with mix and sin functions,<br>
  but have no idea how to get "View vector of camera data".<br>
  I already read <a href="https://blender.stackexchange.com/questions/27764/using-the-camera-data-node">this</a>, and understand what it is, but don't know how to get.</p>
  
  <p>So How can I get "View vector of camera data"?</p>