Debug Block Collision Overlay Reloaded

A client-side mod that adds a new F3 debug overlay showing you exact block collisions, for 1.12.2

About

Features

• Toggleable overlay, default keybind F3 + O.
• Multiple overlay modes, default keybind F3 + I.
• Config file which allows you to set the overlay mode, the level of chat feedback and line rendering settings.
• In-game configuration through Forge that is dynamicly reloaded.
• Has been tested with Cleanroom Loader (0.4.2-alpha) and Celeritas.

Usage

The main way to interact with this mods is by using the F3 + KEY keybinds which by default are F3 + O to toggle the overlay on/off and F3 + I to change the overlay mode.

There is also a config file which is dynamicly reloaded and can be edited in game or on the main menu.

History

This mod was originally created by Phylogeny who original came up with the idea for the mod and released it on September 1st, 2018.

On January 28th, 2026 I came across this mod well developing a ProjectE addon called ProjectE Charms since I wanted a way to see exact collisions on a block I was adding. The problem I found was that actually using the mod was a bit clunky so when I found that the source code was on Github I decided give a crack at improving it, so I forked it.

Subsequently I did the following:

• Rebuilt the Gradle toolchain using ForgeDevEnv.
• Leveraging some custom code I originally wrote for Make Panorama (it can be under the Unlicense since I originally wrote it) transplanted the original handling code to start on improving keybind detection and debounce.
• Removed some janky reflection code and simplified it with an Access Transformer.
• Started reworking the lang file and some of the corresponding code.
• Replaced my single some what scattered keybind handler with two making it both easier to use and develop.
• Finished the lang file rework along with adding two new config options.

Overall this rework only took me about a day with the new 2.0.0 version being done on January 29th, 2026.

Modpacks

You don't need to ask permission or anything to use this in your modpack.

Issues

If you notice an issue and want to make me aware please report them on the issues tab.

Pull-Requests

If you want to help fix an issue or improve the mod I am happy to merge pull requests.

Feature additions like additional modes or config options will probably be accepted but new overlays belong in different mods.