Question

I’m trying to put some blur around a sun, to give it a glow effect.

I’m using the method here:

http://nehe.gamedev.net/tutorial/radial_blur__rendering_to_a_texture/18004/

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.

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.

This is the main part I believe that needs adjusting:

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);

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…..

How?

Answer 1

This maybe isn’t a direct answer, to your question, but you shouldn’t focus too much on effects via the fixed pipeline. NeHE tutorials are good, but a bit outdated. I recommend you just skim through the basics and incorporate shaders in your code. They’re much faster and will allow you for creating much more complex effects easier.