The screenshots will explain better than I can. As I go further away from blocks, they loose pixels and get smudged into a blur. This is the way that the game stops itself from loading every pixel when you are far away right? Well it's happening right next to me now. I was playing Minecraft earlier today then I started it up again now, get on my world and everything is like this!
I haven't tried restarting my game yet because I needed to get the screenshots. I'll edit once I have. EDIT Okay. I've restarted and it's still weird. I've also found out that it doesn't happen to transparrent blocks or entities.
Please switch to the default resource pack, and see if it occurs there.