Didn't anybody pay attention in school? This should be fairly straightforward
https://github.com/wwylele/citra/co...984#diff-a656ac74fb8b591b53b4cec7feb89300R428
Just change this to give you 2 side by side images.. (here comes my attempt with huge lack of motivation):
//Edit:
https://github.com/JayFoxRox/citra/pull/30
Obviously untested and requires adding SideBySide to the list of modes. It also currently assumes that your television will stretch the image back to full dimensions and that the image is fullscreen [= no image borders]. Linux users can do this using devilspie, no idea which tools Windows users can use..
I also made some assumptions about the values in the layout, simply because I never worked with that code and was too lazy to compile it.
Keep in mind that this is a hack. For actual 3D Citra would simply render to 2 seperate framebuffers (Left and Right) and your graphics driver would choose how it presents it (using active 3D / time multiplexed, side-by-side, color shifted / anaglyphic, passive 3D / interlaced, .. w/e)