title: OpenGL Simple Blur effect
body: <p>I'm trying to put some blur around a sun, to give it a glow effect. </p>
  
  <p>I'm using the method here: </p>
  
  <p><a href="http://nehe.gamedev.net/tutorial/radial_blur__rendering_to_a_texture/18004/" rel="nofollow">http://nehe.gamedev.net/tutorial/radial_blur__rendering_to_a_texture/18004/</a></p>
  
  <p>Basically, I draw a sphere, it takes the current buffer and grabs it as a texture and redraws it a number of times, stretching it each time. </p>
  
  <p>This works great when the object is in the centre of the screen. However, I want to have it offset to say, the top right. </p>
  
  <p>This is the main part I believe that needs adjusting:</p>
  
  <pre><code>glColor4f(1.0f, 1.0f, 1.0f, alpha);                 // Set The Alpha Value (Starts At 0.2)
              glTexCoord2f(0+spost,1-spost);                      // Texture Coordinate   ( 0, 1 )
              glVertex2f(0,0);                                    // First Vertex     (   0,   0 )
  
              glTexCoord2f(0+spost,0+spost);                      // Texture Coordinate   ( 0, 0 )
              glVertex2f(0,480);                                  // Second Vertex    (   0, 480 )
  
              glTexCoord2f(1-spost,0+spost);                      // Texture Coordinate   ( 1, 0 )
              glVertex2f(640,480);                                // Third Vertex     ( 640, 480 )
  
              glTexCoord2f(1-spost,1-spost);                      // Texture Coordinate   ( 1, 1 )
              glVertex2f(640,0);
  </code></pre>
  
  <p>For the life of me though, I can't work out how to offset it each time so that the blurred images are not offset to the right. I understand that the whole screen is being captured, but there must be a way to offset this when the texture is drawn.....</p>
  
  <p>How?</p>