title: Render large circular points in modern OpenGL
body: <p>I want to render filled circles of a dynamically varying radius around a set of points whose 2D coordinates are stored in a VBO. So far I was using GL_POINT_SMOOTH, but having now shifted to OpenGL 4.0, this option is no longer available. I have seen a similar question <a href="https://stackoverflow.com/questions/17274820/drawing-round-points-using-modern-opengl">here</a> but that doesn't quite suit my need because the centres of the circles in that example are hard-coded in the fragment shader. How would I do this?</p>
  
  <p>At the moment, my vertex shader looks like this:</p>
  
  <pre><code>#version 400
  
  layout(location=0) in vec2 in_Position;
  layout(location=1) in vec4 in_Color;
  out vec4 ex_Color;
  
  uniform vec4 bounds;
  
  void main(void){
      float x = -1+2/(bounds.y-bounds.x)*(in_Position.x-bounds.x);
      float y = -1+2/(bounds.w-bounds.z)*(in_Position.y-bounds.z);
      gl_Position = vec4(x,y,0,1);
      ex_Color = in_Color;
  }
  </code></pre>
  
  <p>And my fragment shader looks like this:</p>
  
  <pre><code>#version 400
  
  in vec4 ex_Color;
  out vec4 out_Color;
  
  void main(void){
      out_Color = ex_Color;
  }
  </code></pre>
  
  <p>With these shaders, I am getting square points.</p>