Example jungle from Jeb (Twitter
Originally Posted by http://twitter.com/#!/jeb_/status/159941276148568064
Jon (@jonkagstrom) wants to add jungle animals later, but they will not be included in today's snapshot
Old worlds will not get errors, but you will need a new world to get jungles
He hasn't been clear whether newly generated chunks could have jungles or not.
UPDATE: From Jens on reddit
Originally Posted by http://www.reddit.com/r/Minecraft/comments/onlrz/if_you_really_want_12_terrain_in_11_worlds_for/
If you really
want the jungles in your 1.1 worlds, you can trick the game to use the new generator by editing the level.dat file with a NBT editor.
The game looks for the tag called "generatorName", and if it's "default" it will also check "generatorVersion" (if it's available). If the version is 0, it will replace the generator with "default_1_1" instead of "default" to switch to the old generator.
To keep the new generator, change "generatorName" to "default" again and set "generatorVersion" to 1. Please note that this will mess up the whole biome randomizer, so it may start snowing in your desert if you're unlucky.
I'm sorry, I didn't intend to hi-jack this thread
. Show him some upvotes!