(Please note: if you have a bad computer, and want to run Pixelmon with little to no lag, you may need to sacrifice some minor graphics. By minor, I mean minor. Little things like rendering items on the floor).
I will present three mods that will make your Pixelmon experience a little more enjoyable.
If you're a modder, chances are you've heard of this mod. Optifine cleans up and overhauls a good amount of Minecraft's rendering code, making rendering that much less laggy. Optifine even allows you to customize the way your game renders under the Settings option in the pause screen. Definitely a good mod to have. It also includes minor features like zooming in.
(WARNING: If you use shaders, changing some options in Optifine WILL break your game! Luckily, Optifine warns you of this before you change your settings).
Highest Version: 1.10
A small simple mod that changes Client-side and server side performance. Unfortunately, this mod is only available for 1.7.10, nothing above or below that. However, it significantly boosts the FPS of your game, and surprisingly rivals Optifine.
Link: There is no Forum post for this mod, and I only give forum posts. It is on CurseForge, however. A quick search on your browser will find it :)
highest Version: 1.7.10
This mod changes the way Minecraft calculates Sine and Cosine algorithms. With this mod, we've seen an average of a 45 percent increase in FPS with this one. Fortunately, this mod IS for 1.10 and below, and works alongside the other ones just fine!
Highest Version: 1.10
These three mods in combination will produce sick (as in good) results. Even though Fastcraft can't be used above 1.7.10, with the other two mods, you probably won't need it.
There are external ways to boost FPS even higher WITHOUT mod usage. I will present 5 methods. Methods 2 and 3 are NOT recommended, however.
1). Allocating more RAM
Minecraft uses RAM to store short-term information. However, the amount of RAM Minecraft can use is limited, so it can't store a whole lot of short term information such as chunk, block states, item positions, etc. You can change that, luckily. Here is a tutorial on how to: http://www.minecraftforum.net/forums/support/unmodified-minecraft-client/tutorials-and-faqs/1871637-tutorial-allocate-more-memory-for-minecraft
(WARNING!!!!!! Do NOT set your RAM usage ABOVE or near your total RAM amount. This may damage your computer! If you want a suggestion, set it at least 3 Gigabytes BELOW your total RAM amount)
2). Upgrading your Graphics Card
As mentioned before, this method is not recommended, as it costs money. The graphics card is the part of the computer in which graphics are processed. Upgrading your graphics card will in turn make Minecraft render faster, meaning less lag. You'll have to do research on graphics cards, however.
3). Upgrading your RAM
RAM, as mentioned before, stores short term information. So, the more RAM you have, the more your computer can hold information for a little while, such as positions of entities or chunks or whatever.
The FPS increase depends on your "to and from". If you're going from 4 Gigabytes of RAM to 12 Gigabytes, you'll see a major improvement. However, if its from 8 to 12, you won't see too much of a change.
4). Close background operations
All programs will use RAM. The more programs open, the less RAM Minecraft can use. So, close background programs! If you have a phone, use that to research in-game stuff instead of your computer!
5). Reduce existing enhancers
Anything like Shaders or high quality Resource Packs can strain Minecraft, making it have to do more work. IF all else fails, and your game is STILL for whatever reason below 45 FPS (which is the minimal goal), remove such enhancers! Gameplay > quality, because what's the point in good graphics if the computer is going to squeal trying to process them? :p
Those some external ways you can help speed up the game, but there are also a few more internal ways. Mr Masochism says,
...here are a few pixelmon options that modify running speed as well. Specifically low-res textures (impacts graphics memory usage in particular and can provide a significant increase in performance on some machines) and smooth shading on/off (turning this off actually makes pixelmon perform worse). Also minecraft's VBO option is a hugely beneficial performance boost if your graphics card supports it
So, by having low-res textures (found in the Pixelmon config file), smooth shading on (found in the Pixelmon config file), and VBO on (found under Minecraft settings), you can boost the performance of your computer even more!
I hope this is helpful to people, it took a bit of time and testing to present this. If you see any inaccuracies at all, please reply down below, I'll be glad to fix it. Shout-out to Mr Masochism, forum administrator and head of the Pixelmon development team, for adding three more ways to boost performance. Keep an eye out on this topic as we look for more ways to up your FPS.
Have fun catching them all!
Model Rater, Pixelmon Tester, Official Forum Supporter, Gym Development Member!
Not the Pokemon we need, but the one we deserve.