Color Correction shaders for 3DS

[Masaru2]

Title explains it all. The 3DS version of the emulator doesn't have support for color correction shaders, unlike something like Open_agb_firm which implemented it a few months ago.

[Squall-Leonhart]

3DS doesn't support Fragment shaders, so no, open_agb_firm did not implement color correction via shaders, it is a C++/ASM implementation using the values from the shader.

[endrift]

I had some discussions about how to do thus a while ago with various people but came to the conclusion that doing anything like this in software would add significant enough overhead that it would slow down the already borderline emulation. It's one of the reasons the RetroArch version of mGBA is much slower on 3DS. Further, as pointed out, the 3DS lacks a way to do this properly in hardware, so there isn't really a good option. Unless I can get mGBA to be much faster on 3DS I'm not sure this is in the cards.

[profi200]

At least on New 3DS it might just about work. But you need very fast RAM for the lookup table and using a dedicated core for the conversion is a good idea too.

I obviously have all of that in bare metal + the GBA hardware. To further reduce overhead i do the conversion in tandem with DMA. Ugly but brings the overhead down to 800 µs or so worst case.