I'm currently developing a terrain engine for my new project, and I got some interesting result for my manual face culling:
As you can see, there is a Dirt and a Grass face on a Stone block.
Here is my code:
Chunk faceculling: http://pastebin.java-gaming.org/a88270e015d
Cube mesh building: http://pastebin.java-gaming.org/8a882979e41
And I can't get it working properly... :/