I believe that Optifine is a must have mod, even if you dont play with custom textures, it does so much to make the game smooth, and provides many more video options to allow you to fine tune your game to your hardware.
However Optifine isn't just video options, it adds things such as random mob textures, CTM textures, Shaders & GUI customization. and that's where the good stuff comes in!
With the addition of shaders comes the use of specular and normal mapping textures, these types of textures are how I get my bioshock rapture build to look the way it does.
Step 1: Download the latest version suitable for your version of Minecraft Java Edition.
*WARNING* when you click the links to download Optifine, it will take you to a site that hosts ads, do not click on anything within the ad area and if a popup asking you to download something appears, do not download or install that something. At the top right of the ads page is a "skip" button after a countdown, that skip is the only thing you should be clicking on, it will then bring you to the actual download page of Optifine.*WARNING*
Step 2: Run Minecraft and make sure it is working as intended. Close Minecraft afterwords.
Step 3: Double click the Optifine file you downloaded ( it'll be named something like Optifine_1.16.5_HD_U_G7) , it'll open a popup asking you to install or extract, choose install
Step 4: Once installation is complete close the popup and load your Minecraft Launcher, "Optifine" will be a new profile waiting for you.
Now you've installed it, new options should appear in your video options in-game, go ahead an change these to your required settings. one thing I suggest is turning off MipMaps.
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