Blur

I'm attempting to blur the entire screen by:

cameraviewport camera,0,0,256,256
renderworld
copyrect 0,0,256,256,0,0,backbuffer(),texturebuffer(blur)

but it produces a blur which is offset slightly dependant on the camera pitch. What am I doing wrong here? I tried changing the texture dimensions to 320,200, but it doesn't help.

I have no idea what kind of offset you're referring to. And even if I did I'd still need you to post a demo. I've never heard of this issue.

is texture "blur" appied to a sprite or quad?

applied to a sprite. But it doesn't matter anymore. Sorry about the vagueness of my first post. Vagueness helps no man.

I'm thinking of rendering the screen to an image 32x32, then scanning it pixel by pixel and reading brightness values. Then, if a value is over a certain amount, draw a sprite to that position on the real scene. This should be pretty blurry, but any bigger an image res, and the algo will be too slow. What does everyone think?