I've been told that rendering at 32 chunks render distance requires upping your allocated RAM to 2Gb, i have done so. The game still lags like a sedated tree-sloth when I'm at 32 chunks...I have tried it at 4Gb as well, and didn't notice much difference.
There is an extremely widespread misconception that more RAM can solve performance issues; RAM doesn't work like that at all; if there isn't enough RAM the game throws an out of memory error and crashes. They are probably confusing it with what happens if your whole computer runs out of RAM; the OS will start paging memory to disk, which has a huge performance hit - but no individual user program that I know does its own memory paging if there isn't enough RAM allocated to it, including the Java Virtual Machine (actually, most user programs have no need for the user to allocate memory, one of the biggest flaws of Java; if Minecraft had been written in C++ you'd never need to worry about RAM unless your computer started paging to disk and that would tell you the maximum render distance you could use).
1. If you have 32-bit java update immediately to 64-bit java if your graphics card allows. 64-bit runs the current game better and can reduce lag.
2. Disable some graphics options: like setting particles to minimum, turning rain off, setting graphics from "fancy" to "fast", (literally looks almost no different except for lighting algorithm. ), etc...
Honestly, I find it to look better to leave graphics options up high (except I run on fast) and only render 16 chunks or less. This is plenty of distance to be able to explore and play the game. My computer can run at 32 chunks but I still don't do it because it seems unneccessary. I don't feel like taxing my system just to be able to see a bit farther. 16 is plenty.
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