How to randomly generate terrain?

[Moneypro456789]

Hi Guys, so I was wondering that how come terrain generation works for Minecraft, it’s Perlin Noise, I know, but my question is different. How come they generate different ores with normal blocks ? I even see many games on Roblox doing that, how to achieve that ? Thanks

[ketrab2004 (ketrab)]

First they generate the terrain normally, filling all of the underground with stone and caves with air.

Then they create some perlin noise for a specific ore, they check every block whether it’s above a certain threshold and whether there is stone at that block. If both conditions are met then they replace the stone with the ore.