Everything is perfectly visible. Caves, the Nether, and the End appear lit, and underwater areas are crystal clear. Mechanism:
In the Minecraft menu, select the Fullbright pack to move it to the "Selected" side and click "Done". Optional (OptiFine): While some packs work without it, using OptiFine 1.12.2 fullbright 1.12.2 resource pack
Because it only changes brightness textures, it rarely causes lag or FPS drops, making it ideal for low-end PCs. Installation Guide for 1.12.2 Download a 1.12.2 compatible Fullbright pack (often titled FullBright3.zip or similar for older versions) from sites like CurseForge Locate Resource Pack Folder: Open Minecraft 1.12.2, go to Resource Packs Open Resource Pack Folder Drag and drop the downloaded file into this folder. Everything is perfectly visible