Blocks loading in wrong, in patch 1.15.2 ive gone down from 400fps to 30fps because blocks are loading in with a outline and it looks horrible

Duplicate of MC-1794.

Fix:
This issue can usually be fixed by tweaking the game's video settings or the settings of your graphics driver. You can check whether the following workarounds work for you:

• Nvidia: Choose "Let the 3D application decide" in "Adjust Image Settings with Preview" in the NVIDIA Control Panel

• Disable "Anisotropic Filtering" in graphics driver settings

• Disable "Antialiasing" in graphics driver settings

• Set "Mipmap" to 0 in Minecraft's video settings