Introduction to decomp modding

Decomp, or papermario, refers to the Paper Mario decompilation. This is a project which contains reverse-engineered C code which can be compiled into the original game ROM.

Decomp modding is initially harder than Star Rod modding, but it is significantly more powerful. You can write C instead of assembly and modify any engine function or script source code directly without using patch files.

Decomp modding also supports versions other than the US release: JP, PAL, and iQue. At time of writing, only the US release has been 100% matched so we will only discuss modding US here.

Text editor

We recommend using Visual Studio Code. When opening the repo, a popup will appear asking if you want to install recommended extensions - make sure you click Yes.

Image editor

Sprites and textures can be edited in your favorite image editor. Bear in mind that all sprites and most textures use a color-indexed image format with strict limits for the number of colors per image (16 for sprites, 16 or 256 for textures). Many artists prefer using aseprite or libresprite for creating pixel art which can be exported as a color-indexed PNG.

BGM editor

Mamar lets you create and edit BGM files from MIDI files.

Star Rod

Star Rod has a decomp mode which is triggered by opening the decomp repo as the mod folder. This allows you to use Star Rod to edit maps and sprites.