Please show off what crt shaders can do!

hunterk · 9 July 2020 18:35

I believe the curvature is a function of the total depth of the tube from the surface to the electron gun. The electron beam needs to hit the phosphor at ~90 degree angle, so the curvature is used to maintain that perpendicularity across the surface of the screen vs the point-source of the gun.

There were some comparatively very shallow models made toward the end of the CRT heyday, but they suffered from poor convergence and a blurrier image as you approach the corners and the angle of deflection increases.

tl;dr, perhaps LinerCRT is fond of very shallow displays that need that heavy curvature to maintain consistent picture quality.

1001010 · 13 July 2020 09:56

Z-Fast is lightweight and fast. The mask is similar to that of a Trinitron TV.

Nesguy · 14 July 2020 21:53

I used zfast on the raspberry pi before I built a proper emulation PC; it’s a decent shader if you lack the power to run better shaders. I prefer it to the crt-pi shader. Looks like a Trinitron TV at 720p, looks like a PVM at 1080p. The phosphor emulation isn’t accurate but it does a decent job of conveying the aperture grille texture. I’m not the biggest fan of that scaling, though- it’s too sharp. Guest-dr-venom with horizontal sharpness at 3.00 and subtractive sharpness at 1.00 is more accurate than any other shader with the possible exception of CRT Royale (with certain settings). All other shaders have the problem of being either too sharp or too blurry no matter what you do, or the scaling results in ringing artifacts, etc.

Zfast also lacks good color management options, but you can just add grade for that.

lfan · 15 July 2020 01:00

Could someone convert the Z-Fast shader to slang?

hunterk · 15 July 2020 02:04

I did this just today, coincidentally: https://github.com/libretro/slang-shaders/commit/375c6220d7da007bba8da2726d12d516e3a2da24

1001010 · 16 July 2020 10:52

Here is Z-Fast combined with pass2 from gtu-v50 just to blur the image.

Nesguy · 16 July 2020 19:05

That looks decent with that particular content and gtu is a nice older shader. However, anything sprite-based will have overly blurred high-contrast edges, which can have a bad effect on the artwork. Details like small text, small icons, drop shadows, etc will also be overly blurred with such settings. On a (well-maintained) CRT, high-contrast edges remain nice and sharp. That’s why you need something like guest-dr-venom’s subtractive sharpening. CRT-royale has bicubic sharpening which does something similar (they might actually be the same thing, not sure tbh).

@hunterk can bicubic-sharp be ported to glsl and slang, and can parameters be added to adjust the level of sharpening?

Edit: here are some examples illustrating what I’m talking about.

horizontal sharpness 3.00, subtractive sharpness 1.00

horizontal sharpness 3.00, subtractive sharpness 0.00

horizontal sharpness 3.00, subtractive sharpness 1.00

horizontal sharpness 3.00, subtractive sharpness 0.00

hunterk · 16 July 2020 21:14

Sure, done. Lower Bs and higher Cs make it sharper at the cost of ringing. 0.333 is the default for both (the Mitchel-Netravali coefficients, whatever that means).

bicubic-sharp is B = 0.1 and C = 0.5

bicubic-sharper is B = 0.0 and C = 0.75

Nesguy · 17 July 2020 15:40

I guess we don’t actually need to add bicubic sharpening to zfast? It didn’t seem to do anything, after all. The blur/scaling in zfast already does a decent job of keeping high-contrast edges sharp.

Something about the blurring/scaling in zfast doesn’t sit right with me, though. It seems like zfast is blurring using the regular sRGB color space instead of blurring in linear gamma sRGB color space (I might have this backwards), so you get weird-looking stuff like the text and the border around Link’s shield in the below example.

Zfast-crt, horizontal blur 1.00

Guest-dr-venom, custom settings

DevilSingh · 19 July 2020 14:09

Some N64 and DS pics using Kurozumi’s Guest-Dr-Venom preset!

Nesguy · 21 July 2020 21:08

Kurozumi’s preset has some soft clipping and a lot of banding, and contrast seems to be pretty lacking. Compare these two images.

my guest-dr-venom settings.

How does one contribute a preset, anyway? @hunterk

hunterk · 21 July 2020 21:20

that’s a bit of an apples-to-oranges comparison, though, to be fair He’s going for the wide, black gaps rather than maximizing dynamic range. Ideally, we’d be able to do both, but we’re limited as you well know.

Just make a PR on github and put it in the “presets” directory. Yours would be good to have in there.

DevilSingh · 22 July 2020 04:16

I really-really like your preset, that’s what my own GBA preset (pics posted previously) is based on.

But, I can’t use your preset outside of RA in ReShade as it requires @Dogway’s Grade shader (which is not available for ReShade at the moment). Without it the preset just doesn’t look right.

I’d love it if you can post a version of your Guest-Dr-Venom preset without Grade in it.

Nesguy · 22 July 2020 18:58

True, you just can’t have both until we have access to much brighter displays. Now I’m working on something a bit more BVM-like, maximizing the black gaps while minimizing clipping and eliminating the banding (which I think was caused by the mask being used). I increased the beam shape high parameter to 45.00 by increasing the maximum range for the parameter, among other things. Here’s a preview. It should go without saying that the LCD backlight should be maxed out for this (as it should be for the Kurozumi preset as well, and for all my presets). Feedback is welcome.

Thanks for the info! I’ll upload my dynamic preset and this new one after it’s more or less finalized.

@DevilSingh

Glad you like it, and I like those GBA pics but they might be a tad washed out, at least on my display. Admittedly, I’m not familiar with those games and that just might be how they’re supposed to look. Are you using grade with the GBA preset? The sigmoidal gamma in grade is really great for expanding the dynamic range (I just leave it at the default of 0.50). Also, if you raise bright boost beyond a certain point it’ll wash out the colors and eventually result in clipping.

To remove grade from the preset, you can just replace it with stock.slang.

I’ll upload some presets once this new BVM preset is dialed in.

Nesguy · 22 July 2020 19:10

Of course, with a bit more clipping we can make this even brighter. Now it’s starting to look pretty close to Kurozumi’s preset Need to throw a few different games/systems at this and play around with it some more.

Nesguy · 22 July 2020 22:17

This still isn’t finished, but I think I’ve made some decent progress. I expanded the ranges for beam shape low and beam shape high; expanding the range for beam shape high helped a lot (beam shape low, not so much). If you’re willing to do crazy things with gamma, you can get some very thick gaps while still maintaining an adequately bright image and decent saturation and contrast. There’s still some very slight localized bloom with the very brightest colors, but I think this is starting to get pretty damn close to some shots I’ve seen of BVMs. Color temp and such could probably use an adjustment, but I’m not focusing on that right now. I’m going to try expanding the range for gamma input/output, next.

Images must be viewed at full size and with the LCD backlight at 100%.

DevilSingh · 23 July 2020 06:46

Firstly, I should note that those GBA pics I posted before are from the standalone version of mGBA with ReShade. Should have mentioned that when I posted them, lol!

Here’s how your preset looks like with GBA games in RA.

No shaders :

Your preset :

Your preset (with no Grade) :

My GBA preset :

I’ve also tried your preset in ReShade (no Grade obviously) with some PC games and I get the same result as here - overblown whites and bloom, too much saturation (this is probably down to the differences in our displays).

This is the reason I requested a Grade-less version of your preset.

(No idea how those shots look on your end though.)

P.S. - Your BVM preset shots look great. Still very saturated on my display (same as above). Don’t know if its any help, but my monitor is a DELL IPS panel with 2.2 gamma (not that it matters as I use the default 2.4 input/output gamma in Guest-Dr-Venom with no problems)!

DevilSingh · 23 July 2020 06:56

Some Guest-Dr-Venom ReShade test screenshots I took yesterday!

Nesguy · 23 July 2020 23:15

Yeah, something is definitely wrong there. Are you using the preset posted here?

As for the over saturation with the new preset, yeah. Still tweaking it, thanks for the feedback.

How is this looking? Remember to adjust your backlight to 100% and view the images at original size; downscaling does all kinds of horrible things to the image. I also haven’t done any grade adjustments, yet.

DevilSingh · 24 July 2020 04:48

Yes, I’m using the up-to-date preset in the first post from there.

The new BVM screens look great.