/3/ - 3DCG

I was going to ask a question, but I rubberducked the solution myself while explaining the problem and what I was trying to produce. I wanted to make the kind of animated texture you often see in old video games where the texture continuously converges to the center (like a circular pit of quicksand or those holes you drop through in Jabu Jabu's Belly in OoT). It's so easy, I should've realized the solution sooner. Can you figure out how I'm doing this? :)