I've just checked, DOSBox GLSL shaders indeed do not work, but shaders from the libretro pack seem to work fine:
https://github.com/libretro/glsl-shaders

MrFlibble wrote on 2024-01-20, 10:38:

I've just checked, DOSBox GLSL shaders indeed do not work, but shaders from the libretro pack seem to work fine:
https://github.com/libretro/glsl-shaders

I have been experimenting with these shaders. There are couple of decent ones, though those new Dosbox Staging shaders look like the best that exist, at the moment. I am hoping that 86box shader support gets upgraded at some point so that the Dosbox Staging shaders can be used. Or, perhaps added to Shaderglass as that would be another solution. I have been experimenting with that, as well. I am even looking into a video capture solution so that I can connect my retro PCs to that and use Shaderglass over the capture window, though I read that there is frame-lag using this method. It makes me lament that we no longer have ATI All-In-Wonder options. I read that an end user can recompile Shaderglass with added shaders, so I may try to research that. Someone is selling a 19" CRT for a reasonable price, so I am considering making the drive with a laptop with a VGA port with DOSbox and Dune II (for some reason I like to use Dune II as a CRT test game) and check it out. However, I know that is a temporary fix (if it even has a good and bright picture for being 22 years old,) as it will eventually die.

The quest continues, hehehe...

Scythifuge wrote on 2024-01-20, 17:24:

I have been experimenting with these shaders. There are couple of decent ones, though those new Dosbox Staging shaders look like the best that exist

I've been playing around with CRT imitation shaders ever since this option was available in DOSBox SVN Daum. To be perfectly honest, I've not used a CRT monitor since I guess mid-2000s, and I don't remember really well what the screen looked like -- but I vividly remember the moment when I first replaced my CRT with an LCD display and how everything looked different, for example the Windows 98 desktop darkening effect that was achieved by overlaying a checkerboard pattern over the desktop was completely broken.

I gave a quick spin to the libretro CRT shaders in 86Box, and so far I think that crt-easymode is the least intrusive one, while still giving the image a more textured look that seems to be nicer than the default linear filtering or the built-in DOSBox sharpening shader. BTW, I've downloaded DOSBox-X and for some reason it does not use any shaders other than the default one -- perhaps my desktop resolution is not enough for that? GLSL shaders work fine for me in DOSBox ECE.

That said, I've read multiple discussions with opinions from supposedly knowledgeable people who argue that using shaders that produce pronounced scanlines is an overkill for VGA mode graphics and above.

MrFlibble wrote on 2024-01-20, 18:39:

I've been playing around with CRT imitation shaders ever since this option was available in DOSBox SVN Daum. To be perfectly hon […]
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Scythifuge wrote on 2024-01-20, 17:24:

I have been experimenting with these shaders. There are couple of decent ones, though those new Dosbox Staging shaders look like the best that exist

I've been playing around with CRT imitation shaders ever since this option was available in DOSBox SVN Daum. To be perfectly honest, I've not used a CRT monitor since I guess mid-2000s, and I don't remember really well what the screen looked like -- but I vividly remember the moment when I first replaced my CRT with an LCD display and how everything looked different, for example the Windows 98 desktop darkening effect that was achieved by overlaying a checkerboard pattern over the desktop was completely broken.

I gave a quick spin to the libretro CRT shaders in 86Box, and so far I think that crt-easymode is the least intrusive one, while still giving the image a more textured look that seems to be nicer than the default linear filtering or the built-in DOSBox sharpening shader. BTW, I've downloaded DOSBox-X and for some reason it does not use any shaders other than the default one -- perhaps my desktop resolution is not enough for that? GLSL shaders work fine for me in DOSBox ECE.

That said, I've read multiple discussions with opinions from supposedly knowledgeable people who argue that using shaders that produce pronounced scanlines is an overkill for VGA mode graphics and above.

I avoided shaders for a long time while questing for CRTs. This video from Phil's Computer Lab is what is driving me to find a solution (before giving up and just use Dosbox Staging, hehehe...)

https://www.youtube.com/watch?v=lWPI2hox1Qc&t=180s

Scythifuge wrote on 2024-01-21, 01:42:

I avoided shaders for a long time while questing for CRTs. This video from Phil's Computer Lab is what is driving me to find a solution (before giving up and just use Dosbox Staging, hehehe...)

Most CRT-imitation shaders that I've seen greatly overdo their effects. I wish they had a sort of slider to enable only 25-50% of what they're trying to do.

Azarien wrote on 2024-01-21, 11:36:

Most CRT-imitation shaders that I've seen greatly overdo their effects. I wish they had a sort of slider to enable only 25-50% of what they're trying to do.

This. 100%.

I've gained a bit of shader experience over the years, and also got myself a CRT monitor again (late 80s multisync).
It's true that most shaders don't look quite good out of the box, though this is partially because key components are very dependent on the host display. You have to learn and do your own adjustments. Shaders like Geom or Easymode can look ok, but they're really old. The best shaders I've seen because of their flexibility and ongoing development (at least the libretro slang ones) are the ones by Guest.
The old Guest Venom and Guest Venom Fast are available in libretro GLSL format, so they can be used by 86box (from what I've read here, I haven't used it in years) and PCem. It's possible however to use newer Guest Advanced and many other Shaders via ReShade in many emulators. Guest Advanced Reshade port .

I really like Guest Venom Fast though, because it doesn't look too bad out of the box to me, and doesn't have a ton of parameters which you'll never tweak anyway.
One thing you'll need to do (like with many shaders) is to increase the mask strength for authenticity. Unintuitive as these things are, that means lowering "Mask Dark" and "Mask light" parameters. Unless you're using Mask 0, in that case you have to increase "CGWG strength". 😀
As for scanlines, they should shrink with increased input resolution, setting the output to doublescan is something that typically the emulator needs to provide. In ReShade, you can usually specify the scanline height. E.g. setting it the maximum output res you're using should result in no scanlines at all. I found this useful on occasion, since sometimes the output with a shader's own scanlines was a little odd, instead I attached a separate scanline shader.
I guess the bottomline here is that you definitely have to put in some effort to understand how everything works, but you can get some pretty good results in my opinion.