Haha, yeah - although their comment was only considering the 2D case, same as the book. You can make a (very efficient!) diffuser from 2-channel rotations, but

Haha, yeah - although their comment was only considering the 2D case, same as the book. You can make a (very efficient!) diffuser from 2-channel rotations, but you have to tune it a bit to get it smooth without having a slow attack. With more channels, it's much easier to get right.