GenMogrify

World gen transmogrification.... change the world as it is generated.

Blocks, entitities and items can be altered as they are generated.  This mod is intended to be used in mod packs that wish to gate items behind altered recipes to prevent those items from being naturally found in the world.  Want to make furnaces difficult to obtain?  Then you probably don't want them scattered randomly in various structures.

In addition to preventing select things from generating, this mod could be used just to make desired changes you want to see in the world.  Want all grass blocks to be replaced by endstone?  Well, you probably don't.  But if you did, you could.  In fact, the default configuration of changes does just that.... so you probably want to change things to how you want them to be.  The default configuration is generated when loading a world without a configuration already in place.

Documentation is available.  The default configuration can be used as an aid to understanding how the genmogrifications are defined. 

Enjoy.