I am aware that the ‘stock’ shader can be used to set specific x & y resolutions, so as to for example play certain Dreamcast games in 240p which may otherwise only support 480p.
What I’m wondering is, how far do these resolution modifying capabilities go? Could I for example state that y resolution is exactly half of a given input resolution?
Yeah, I think you can by instead of doing an absolute resolution in the shader preset use source, and set it 0.5 which should do a half scale.
Thank you! Since I’m doing intensive work for most of the day I can’t check this out right now, but I’ll try out your suggestion later this evening and report! 
It should look something like this in the preset, I think.
Replace the number before the = with whatever number the stock pass is, in this case the 0’s after the x/y part.
This should do full scale x, half scale y.
scale_type_x0 = source
scale_type_y0 = source
scale_x0 = 1.0
scale_y0 = 0.5
Hunterk or someone will most likely correct this later if it’s wrong.
So, I got around to trying it out, and… well, it worked!
Sorta. I’m fairly sure it did what it’s supposed to do, but it didn’t have the (rather far-fetched) effect I was hoping for. Namely, getting a 2x increased resolution to downscale so as to be recognizable by Switchres. I confirmed the vertical resolution stayed at 448. Bummer. I suppose the shader passes are applied after the fact.
Thanks for the help!
Ohhh yeah I know nothing about switches. You’d have to ask someone else to help with that witchcraft, lol.
Shaders are post-processing, so they indeed will not affect the res-switching, which comes directly from the core.
Sounds like what he’s wanting could be an interesting bounty for some of the 3d cores? Probably require some decent power though, as in some cases you’d possibly be upscaling then downsampling or just downsampling. (Not sure if this would work but it’s an interesting idea nonetheless.)
Is what I’m referencing basically supersampling? (I don’t mess with this kind of thing often.)
It absolutely is! It would have the same effect as the supersampling option in the Beetle HW core. I do this all the time for fixed-resolution 3D systems on my CRT, which only requires manually setting a 240p output resolution. Problem comes from cores that like to switch a lot.