https://hn.algolia.com/?query=3d%20fractal -> https://news.ycombinator.com/item?id=935241 (Nov 2009)

But unless you read HN for 5+ years without creating an account, the exact discussion you recall may be some other search result there.

>mrob: the Wikipedia page is a better starting point: https://en.wikipedia.org/wiki/Mandelbulb

PS. Algolia seems a bit finicky, a couple of these were on the second page of results for the first search: https://hn.algolia.com/?query=3d%20fractal%20comments%3E0&so.... I always hate how they show different results for plurals, but this is a new problem I'll keep in mind (sort by popularity doesn't work?).