This bug is a render glitch in minecraft 1.9 snapshot - 15w36d. this cause the terrain behind you and behind walls relative to you location to not load due to the way minecraft now renders blocks for optimization purposes.

Reproduce this issue by: go in a small wooden building (Maybe 5x5) and stand in the middle or close to the front (without any doors or windows and completely boxed in without any way of seeing out) Then press F5 once. You should see that the terrain behind you in not rendered and you can see beyond the walls where the terrain is also not rendered. It should look like the attached screenshot. Thanks for reading!

EDIT: you must be on the edge of a chunk for this glitch to work!