Odin + Raylib + Hot Reload template

This is an Odin + Raylib game template with Hot Reloading pre-setup. It makes it possible to reload gameplay code while the game is running.

Supported platforms: Windows, macOS and Linux.

Supported editors and debuggers: Sublime Text, VS Code and RAD Debugger.

I used this kind of hot reloading while developing my game CAT & ONION.

Quick start

If you are on Linux / macOS: Below, replace .bat with .sh and .exe with .bin.

1. Run build_hot_reload.bat to create game_hot_reload.exe and game.dll. Note: It expects odin compiler to be part of your PATH environment variable.
2. Run game_hot_reload.exe, leave it running.
3. Make changes to the gameplay code in game/game.odin. For example, change the line rl.ClearBackground(rl.BLACK) so that it instead uses rl.BLUE. Save the file.
4. Run build_hot_reload.bat, it will recompile game.dll.
5. The running game_hot_reload.exe will see that game.dll changed and reload it. But it will use the same Game_Memory (a struct defined in game/game.odin) as before. This will make the game use your new code without having to restart.

Note, in step 4: build_hot_reload.bat does not rebuild game_hot_reload.exe. It checks if game_hot_reload.exe is already running, and if it is, it avoid recompiling it, since it will be locked anyways.

Description

build_hot_reload.bat will build game.dll from the odin code in the game folder. It will also build game_hot_reload.exe from the code in the folder main_hot_reload.

When you run game_hot_reload.exe it will load game.dll and start the game. In order to hot reload, make some changes to anything in the game folder and re-run build_hot_reload.bat.

game_hot_reload.exe will notice that game.dll changed and reload it. The state you wish to keep between reloads goes into the Game_Memory struct in game/game.odin.

There is also a build_release.bat file that makes a game_release.exe that does not have the hot reloading stuff, since you probably do not want that in the released version of your game. This means that the release version does not use game.dll, instead it imports the game folder as a normal Odin package.

build_debug.bat is like build_release.bat but makes a debuggable executable, in case you need to debug your non-hot-reload-exe.

Sublime Text

For those who use Sublime Text there's a project file: project.sublime-project.

How to use:

• Open the project file in sublime
• Choose the build system Main Menu -> Tools -> Build System -> Game template (you can rename the build system by editing project.sublime-project manually)
• Compile and run by pressing using F7 / Ctrl + B / Cmd + B
• After you make code changes and want to hot reload, just hit F7 / Ctrl + B / Cmd + B again

RAD Debugger

You can hot reload while attached to RAD Debugger. Attach to your game_hot_reload executable, make code changes in your code editor and re-run the the build_hot_reload script to build and hot reload.

VS Code

You can build, debug and hot reload from within VS Code. Open the template using File -> Open Folder....

Requirements for debugging to work:

• Windows: C++ build tools
• Linux / Mac: CodeLLDB

Launch with Run Hot Reload launch task, see image above. After you make code changes press Ctrl + Shift + B to rebuild and hot reload.

Windows Debugging hacks

On Windows the degugging while hot reloading works by outputting a new PDB each time the game DLL is built. It cleans up the PDBs when you do a fresh start. See build_hot_reload.bat for details.

Demo streams

Streams that start from this template:

• CAR RACER prototype: https://www.youtube.com/watch?v=KVbHJ_CLdkA
• "point & click" prototype: https://www.youtube.com/watch?v=iRvs1Xr1W6o
• Metroidvania / platform prototype: https://www.youtube.com/watch?v=kIxEMchPc3Y
• Top-down adventure prototype: https://www.youtube.com/watch?v=cl8EOjOaoXc

Atlas builder

The template works nicely together with my atlas builder. The atlas builder can build an atlas texture from a folder of png or aseprite files. Using an atlas can drastically reduce the number of draw calls your game uses. There's an example in that repository on how to set it up. The atlas generation step can easily be integrated into the build bat / sh files such as build_hot_reload.bat

Questions?

Ask questions in my gamedev Discord: https://discord.gg/4FsHgtBmFK

I have a blog post about Hot Reloading here: http://zylinski.se/posts/hot-reload-gameplay-code/

Have a nice day! /Karl Zylinski