title: How to get a value from vec3 in vertex shader? OpenGL 3.3
body: <p>I have the following vertex shader:</p>
  
  <pre><code>#version 330                                                                      
  layout (location = 0) in vec3 Position;                                           
  uniform mat4 gWVP;                                                                
  out vec4 Color;
  void main()                                                                       
  {                                                                                 
      gl_Position = gWVP * vec4(Position, 1.0);                     
  };
  </code></pre>
  
  <p>How can I get, for example, the third value of vec3? The first my thought was: "Maybe I can get it by multiplying this vector(Position) on something?" But I am not sure that something like "vertical vector type" exists.
  So, what is the best way? I need this value to set the color of the pixel.</p>