So I decided to use multimc to play with mods in singleplayer. I fired up a world with the seed 1 (yes just 1, it spawns you near a jungle). It started off incredibly laggy. Not like framerate, but like multiplayer lag. It was agonizing just hitting a mob, thanks a lot, release 1.3. It took about 8 solid seconds for the mob to drop xp after dying. Anyways, when I started to explore the world, things got a little odd. At first I thought maybe it was my graphics card or something. But nope. Apparently, OpenGL was running out of memory. I got insane graphical spikes pointing into the sky, one dimensional walls, and... rainbow blocks? I broke one of the rainbow blocks, and it disabled my sound! After flying around for a bit, I came across some untextured mobs, pure white and devoid of any detail. Very creepy and strange. Then I kept getting this error: OpenGL Error: 1285 (Out of memory) Also, I took screenshots BUT THEY DIDN'T SAVE! All I got was the same screenshot of me looking at the ground to reduce spawn generation lag about 15 times. So unfortunately, I have no way to show you what was even going on. Just take my word for it, it looked like an acid trip.