Fix RetroBat/RetroArch Emulator Scaling on Ultrawide Monitor

— Gaming
Screenshot of game running at full size with arrows emphasizing this fact

RetroBat is a Windows-specific solution for running EmulationStation and RetroArch, along with other emulation software. I normally run it on a PC connected to my main TV where I can also run Steam in Big Picture Mode for more modern games. However I recently set up RetroBat on my gaming desktop, which has a 21:9 ultrawide monitor. Using the default settings, when I launched games I was seeing black space all around the game. It wasn’t scaling up to fit my monitor.

Screenshot of game running too small with black around all four sides
This is a screenshot of my ultrawide monitor running the Megadrive core and a shader to mimic the look of a CRT (the shader has no effect on the scaling of the game).

At first I tried changing the video resolution setting, then I tried changing the bezel setting, and even used a few different shaders–including no shader at all–but none of this fixed the issue. Finally, I changed the global setting for Game Settings > Game Aspect Ratio to “Core Provided,” and that resolved the problem!

Screenshot of EmulationStation setting to change Game Aspect Ratio to Core Provided
Here I changed the Game Settings > Game Aspect Ratio to use “Core Provided,” which should use the appropriate aspect ratio for each emulator core (i.e. 4:3 for most systems).

I could still use whatever shaders and bezels I wanted without any problems. Maybe RetroArch expects to be used on either a 4:3 or 16:9 screen and does not gracefully handle ultrawide resolutions by default? Regardless, it’s still a great piece of software!

Screenshot of game running full size
All fixed now, and looking good with the DIUMON-BEZEL-PROJECT-ADVANCED shader.

I would also recommend trying some different shaders that mimic how a CRT television looks for older systems. There are several resources and videos that illustrate this in more detail, but the TL;DR of it is that game artwork for older systems was crafted for the look of a CRT. Artists at the time took advantage of things like bloom, pixel bleeding, and the overall “inaccuracy” of the technology. There are numerous shaders and presets that try to mimic this look. Whether this looks good is subjective of course, but that is why it is so nice to have different options for which shaders to use (or not use).