why when i play minecraft my fan turns on loud and my macbook gets hot?

This isn't really a problem. When your fan turns up that simply means you're making your Mac workout (:3) this is perfectly normal when playing games but make sure you are playing on a flat surface that can let airflow get to fans (eg. don't play on your lap it burns. And do not play on fabric it will burn your laptop).

Despite it "blocky " appearance, rendering all that eye-candy takes a lot of Processor and GPU power.

Try backing off the Video settings inside Minecraft, e.g., shorter rendering distances, and see if that helps.

Not only that, macs aren't made for gaming really. Most games will take up a lot of video processing and your RAM. (Certain ones will use your CPU a lot but minecraft doesn't really). As Grant said, try lowering the video settings and if you have a high performace graphics card built into your mac as well as the integrated one, select to only use the high performace. (although I think thats only with the mid-2012 mac models).

I think one of the main problems with the MacBook Pro is the fan location. The outlet is right at the joint of the body and display, therefore at the prime position for heat and stress. But anyway, I would purchase a laptop cooling tray or fan tray if the problem continues.

Macs aren't really designed for gaming. Even my 10 year old home PC plays Minecraft better than a 2013 mac. the best option is to buy a PC, but if you only have a mac, here are a few options:

If you are running OS X Sierra, then turn night shift on. This can be found at System Preferences, on the Displays tab.

My top 6 solutions are

1. Turn Brightness down.

2. Turn Keyboard Brightness down.

3. Turn off apps you aren't using

4. Using Activity Monitor to find out which apps are taking up the most energy

5. Get Dr. Cleaner Pro. It is a hefty price at $15, but it can save a ton of memory usage, and it also doubles as a file cleaner and duplicate remover. (There is a free version, but it doesn't have nearly as many features as Dr. Cleaner Pro)

6. Get MalwareBytes, as viruses tend to take up a lot of memory. Many people say it is a virus, but my school has top grade technicians, and they recommend that we use it.

I hope this helps you!

Put a wooden surface under the laptop, for example a clipboard. If you use your laptop on certain materials, they can soak up the heat generated by the fan and cause the computer to lag.

If you can create an air space under your MacBook (about 3/4 inch /20mm minimum) it can start a convection current to improve cooling.