A tiny GBA Jam 2021 just-for-fun submission celebrating the 20th anniversary of the GBA (16.7 MHz!) and other things. It's a small audio-visual demo/toy which uses broken and naive 3D software rendering.
Requires libtonc (which should come with your devkitARM installation).
Apex Audio System for .mod playback is included in lib/apex-audio-system, you only have to invoke make in that directory, and then you shouldn't have to worry about it anymore. (You might have to change the AAS Makefile by updating export CROSS = /opt/devkitpro/devkitARM/bin/arm-none-eabi- if your devkitARM installation is in another place. Refer to the AAS documentation for detailed build instructions.)
You can change the mGBA binary to be used in the top-level Makefile by changing the path in MGBA := /Applications/mGBA.app/Contents/MacOS/mGBA to the location of your own local mGBA installation. This way, you can just invoke make run to build and run your code with the correct flags etc.
Make sure that your $DEVKITARM environment is set up correctly.
We also assume you use mGBA, as assertions and performance monitoring work via mgba_printf (see Credits).
For code generation and .obj import, you need an installation of python3 (I think at least 3.6, since we use f-strings etc. extensively; I personally tested with python 3.9.)
The game-jam specific code, or the actual content, is located in the source/scenes directory, while the "engine" (broken rusty bicycle would be a more appropriate description) resides in source and source/render.
To make something on your own, I'd just look at an existing scene of your liking. You can call python3 tools/sceneCodegen.py --new "test" --mode 5 to automatically generate new scene template files called testScene.c and testScene.h in the source/scenes directory, which you can then modify and use to your liking.
If you modify source/scenes/config by setting another startscene, if you remove a scene, or if you add a scene manually, just run python3 tools/sceneCodegen.py without arguments (which then takes care of generating the appropriate code, such as the setup of the appropriate function pointers and sceneIDs, which allow you to refer/switch between scenes from another scene for instance).
source/scene.h contains a description on what the functions/function pointers of a scene actually do.
Note that mode 5 in this broken bicycle actually refers to a scaled and letterboxed version of mode 5. (Just pretend mode 5 has a resolution of 160x100 pixels, okay?) More on that in the comments of source/render/draw.c. You can also use mode 4 (just regular, plain old mode 4 as you know it), but other modes are not implemented yet. Keep in mind that all our 3d drawing code (i.e. the interesting stuff) is only implemented for mode 5 so far, though; but it should be reasonably easy to implement that for mode 4 by changing some constants and logic in source/render/draw.c, source/render/rasteriser.h and source/camera.c if you desire that.
For debugging, it might be useful to #define USER_SCENE_SWITCH in source/scene.c, which you can use to cycle through scenes with a key sequence (a cheat code essentially). That sequence can be changed in the same file.
Put your .mod files into assets/music. Just invoking the top-level Makefile with makewill take care of them (look at the examples).
Put your 3d models into assets/models. As above, just invoke make (it internally uses python3 tools/obj2model.py to convert your .obj files). You can also use .mtl files (the names must match). So far, multiple objects in one .obj file are treated as one (sorry).
I assume you use blender 2.8 in the following. Make sure to use the Principled BSDF (only its Base Color is considered) surface/material type in Blender, as the Background (and other) surface types won't be exported. Make sure to triangulate your faces, and make sure you decimate your models (up to 350 triangles might be workable I guess, but the lower, the better). Make sure the backface-culling checkbox is checked under the materials (if you want that).
On export in blender, make sure to check Write Normals, Write Materials, Triangulate Faces (if you haven't already with a modifier), and uncheck Include UVs (if possible).
We use instanced models, and organise them in object pools. Pretty unnecessary. In the end, you can just access them through buffers, though. Please look at the example code, more documentation may follow.
There's a lot. It'd be probably better to just start from scratch and let this be. Learned a lot, though!
Based on a big amount of work of other people. Please respect the licenses of the respective code etc., even if the rest of this repository is licensed under aforementioned MIT License (MIT).
All the code which is not owned/licensed under other terms is licensed with The MIT License (MIT) [1] (but you must respect the respective licenses/restrictions which apply to the work of other people such as credited in Credits). All assets (music, all 3d models except suzanne.obj and cpa.obj) are licensed under CC BY (Attribution 4.0 International (CC BY 4.0)). [2]
[1] https://mit-license.org (last retrieved: 2021-07-10)
[2] http://creativecommons.org/licenses/by/4.0/ (last retrieved: 2021-07-10)