| OpenBOR Native Component | libretro Implementation | |--------------------------|-------------------------| | Win32/SDL Main Loop | retro_run() callback | | DirectInput/XInput | retro_input_state() polling | | DirectSound/ALSA | retro_audio_sample_batch() | | OpenGL/Direct3D | retro_video_refresh() with framebuffer | | File I/O ( fopen , ReadFile ) | retro_vfs (Virtual File System) |
Abstract: The OpenBOR (Open Beats of Rage) engine is the most versatile homebrew side-scrolling beat-‘em-up engine, powering thousands of fan-made games. However, its native stand-alone executable limits its integration into modern frontend systems. This paper discusses the development, functionality, and performance implications of porting OpenBOR as a libretro core for RetroArch. We analyze the architectural challenges, input mapping, asset streaming, and the benefits of unifying the engine under a single, cross-platform API. 1. Introduction RetroArch has become the de facto standard for emulation and game engine unification through the libretro API. By abstracting video, audio, input, and storage, libretro allows disparate emulators to run within a single interface. OpenBOR, originally derived from Beats of Rage (a Streets of Rage fan game), has evolved into a powerful, script-driven engine capable of running custom 2D action games. retroarch openbor core
Historically, OpenBOR operates as a stand-alone .exe (Windows) or .app (macOS) that scans a /Paks/ directory. The RetroArch OpenBOR core seeks to eliminate this friction by treating OpenBOR .pak files as "roms" that can be launched directly from RetroArch’s playlist system. The libretro OpenBOR core is not a recompilation of the original C code but rather a libretro wrapper around the OpenBOR engine’s main loop. | OpenBOR Native Component | libretro Implementation |