I wouldn't normally make a post like this to clutter HN, but I've searched for hours now under every possible thing I can think of...

It was a series of 6 video "tutorials" (but more they were just cool demos) of this software this guy made which allowed you to manipulate wave forms and do cool things to them (like photoshop but for math).

In the 6 or so videos he builds roughly off of what was in the last video, and he shows how to use tangent waves, sine waves, staircase pattern.. then he combines them and meshes them into creating a "randomized world" that could create something similar to minecraft with hills, valleys, but they look natural.