Creating Custom Content: Step-by-Step with the Garry’s Mod Addon Tool
Overview
This guide walks through creating, packaging, and installing a simple Garry’s Mod addon using the Addon Tool (gmad/gmpublish or in-game tools). It assumes basic familiarity with Garry’s Mod file structure and a text editor.
What you’ll create
- A simple Lua scripted entity that spawns a colored cube.
- Basic textures and a model placeholder (prop_physics cube).
- A working addon folder packaged as a .gma suitable for local use or publishing.
File structure (example)
- my_custom_cube/
- lua/
- entities/
- my_cube/
- init.lua
- cl_init.lua
- shared.lua
- my_cube/
- entities/
- models/ (optional)
- materials/
- models/
- my_cube.vmt
- models/
- addon.txt (metadata)
- lua/
Step-by-step
- Create addon folder
- Create folder named my_custom_cube in your Garry’s Mod addons directory or a workspace folder for packaging.
- Add addon metadata
- Create addon.txt with fields:
- “title”: “My Custom Cube”
- “type”: “gamemode” or “swep”/“tool” as appropriate (for entity use “server” + “client” via Lua files)
- “tags”: [“utility”]
- “ignore”: []
- Write shared entity file (shared.lua)
- Define basic entity properties (Base, Type, PrintName, Author, Spawnable).
- Example: set Model to “models/props_junk/wood_crate001a.mdl” or a cube prop.
- Write server init (init.lua)
- Implement Initialize to set model, physics, and color.
- Implement Use or Think as needed.
- Write client drawing (clinit.lua)
- Optionally add client-side effects or HUD hints.
- Add materials/textures
- Place VMT/VTF files under materials/models/ and reference them from the model or via SetMaterial / SetColor.
- Test locally
- Place the folder in garrysmod/garrysmod/addons/ and launch Garry’s Mod.
- Use the spawn menu or console commands to spawn the entity and debug errors via console.
- Package with gmad
- From Garry’s Mod bin folder run:
Code
gmad.exe create -folder “path\to\my_custom_cube” -out “my_custom_cube.gma” - For Linux/mac use the corresponding binary.
- Install or share
- Install locally by placing the .gma into garrysmod/garrysmod/addons/ or upload to the Steam Workshop using gmpublish or the in-game publishing tool.
Quick troubleshooting
- Lua errors: check garrysmod/garrysmod/lua/errors.txt and the game console.
- Missing textures/models: confirm paths and that files are in the right folders.
- Entity not spawnable: ensure Spawnable = true and AddCSLuaFile() where needed.
Tips & best practices
- Use AddCSLuaFile() in shared files to send client code.
- Keep client/server logic separated.
- Test iteratively; start minimal and add features.
- Use descriptive addon.txt metadata for Workshop publishing.
If you want, I can generate the example Lua files (shared.lua, init.lua, cl_init.lua) and a sample addon.txt for this addon.
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