How to create dimension-based spawns

[GiantNuker]

How do I create dimension based spawns if I am using a vanilla entity in a vanilla biome in a custom dimension?

[GiantNuker]

15 hours ago, diesieben07 said:

Spawns are based on biome, they are independent of dimension. If you really wanted to keep the vanilla biome, you would have to do your own spawning.

How do you make them biome & dimension dependent?

 

Edit: if this is impossible, how would I go about creating my own?(I cannot find the vanilla spawning script.)

Edited April 15, 2017 by GiantNuker

[GiantNuker]

7 hours ago, diesieben07 said:

Vanilla spawning happens in WorldEntitySpawner. 

Thank you!