Arc upper lens distortion

Hi! Dude,

Actually I am a perfect beginner of vvvv.
Does anybody let me know the way to make my screen “Arc upper distorted” as below?
Thanks in advance~

oops!
I missed attaching an image.
https://vvvv.org/sites/default/files/imagecache/large/images/arc_upper.jpg

the distorted screen must be the image that I attached!

b-spline?