Quote:

Before blurring you should also downsample the image to 1/4 of its original size. This way the shader is much faster and the result looks much more blurry.


How do you do that?

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com