How is worldgen modified in FTB modpacks?

[bokisis]

So I've always wanted to make packs, and I've actually made packs myself before, but I've never touched worldgen, and I've been wondering how is worldgen modified in FTB modpacks? How do they remove all copper ores and leave only 1 type? How do they increase or decrease the frequency of a certain ore? How is it all done? Thanks.

 

[Vagaprime]

The way that FTB handles it is by using Cofh core. Cofh core will let you set what ore you want to spawn, at what y level you want it to spawn out, and how much per chunk. To get a understanding of hows its done look into something like the direwolf20 configs. You will see that mot of the ore spawn options in other mods have been turned off through their configs and that Cofh core is set to handle ore spawn. The Cofh core ore spawn is set up using a .JSON file.