tiltShift() keeps a band of the picture sharp and blurs above and below it. The eye reads that shallow focus as something small and close, so a whole scene starts to look like a model on a table.
focus is where the sharp band sits, from 0 (top) to 1 (bottom); band is how far it reaches either side and feather how long the fade into blur is, both as a share of the height; radius is how blurred the rest is, in game pixels. The blur is worked out in two passes at half size, like blur().
Move the pointer up and down to place the band, ↑ ↓ to widen it and Space to switch it off.