This is the closest reference I could google.
The article I am talking about had the author explain the various steps he went through, starting with rotating a 2d fractal, and move up the process to finally get the math equations to generate a truly 3d fractal.
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?).
https://christopherolah.wordpress.com/2011/08/08/the-real-3d...