In 14w27a only leaves close to the player are opaque, with all other leaves rendered as transparent. This causes huge performance hits in wooded areas.
Recreation:
1)Launch 14w27a
2)Open any world and find a forest
3)Go to video settings and enable fast graphics
4)Observe leaf blocks rendering incorrectly
Environment
OS: Linux Version 3.8.0-42-generic
Java Version: 1.8.0_05
Dupe of MC-57266