New and Updated Shaders

It's been awhile since I've done any shader posts, so I figured I'd cover some updates that have happened recently. Same format as usual, the only difference this time around is that instead of zooming into screenshots using photoshop, I made them straight from RetroArch using the 'zoom' from my image adjustment shader. This gives sharper, cleaner detail shots. Anyway...

No Shaders (Nearest Neighbor)

Here is a shot with no shaders for comparison.


ScaleFx

Sp00ky Fox had been working on cleaning up artifacts from the Scalenx shaders and, in the process, worked up a similar algorithm of his own, known as ScaleFx. By cranking it up to 9x, he managed to do some pretty impressive smoothing:

Some notable things here: check out the circle-c copyright symbol, which is very hard to deal with in this sort of shader, as well as the straight lines throughout the logo and on the shallow slope below the dragon coin.

He also made a variant, known as scalefx-hybrid-9x, that uses reverse-antialiasing and creates some interesting depth and shading effects:

It does introduce some haloing, though, and is pretty heavy, performance-wise.

xBR-lv2-accuracy-multipass

For the past year or so, Hyllian has been working to improve his now-famous xBR upscaling algorithm, mostly by pairing it with other algorithms and working to improve handling of problematic edge-cases. Very recently, though, he changed the way corners are detected and added a new color diff algorithm, which fixes some weird artifacts that could occur when bright red and bright blue pixels were next to each other (artifacts not pictured):

Here is an older version of the same shader for comparison:

Again, the copyright symbol is a good example of the improvements, along with the circles inside the number 9s. The updated version also works quite well with Playstation-era antialiased images, while ScaleFx works best on bold, cartoony graphics, like Super Mario World and Shantae.

CRT-Lottes Updated

Since we first ported Timothy Lottes' scaling pixel art shadertoy, he did a couple of iterations to add bloom and a few more variations on his awesome shadow mask code. r5 incorporated those updates into our port and threw in some runtime parameters (including the aforementioned mask variations):

This is the default compressed TV-style shadow mask^^.

This is the Trinitron-style aperture grille^^.

This is the stretched VGA-style shadow mask that was used in the original shader^^.

And this is another VGA-style mask with larger phosphors^^.

CRT-Royale-Kurozumi Preset

Shmups user Kurozumi posted some really nice settings for TroggleMonkey's CRT-Royale shader that makes it look very much like a high-res broadcast monitor (e.g., Sony's BVM line or the 800-line PVMs):

I put these settings into a cgp preset, located in the 'cgp' subdirectory of the main common-shaders repo.

More CRT Shaders

There have been a number of new CRT shaders written since I last did a big roundup, and some people have asked about it, so here we go! All Cg-format shaders are available in libretro's common-shaders repo on github, while all Quark shaders are available in my github repo. All shots were taken at 4x scale factor, and the closeups are scaled up 400% with nearest-neighbor. Click the thumbnails to embiggen:

CRT-Geom

I've already written about this one at length, but I figured I'd include it here anyway for reference and comparison. It's the original awesome CRT shader written by cgwg with some help from Themaister and DOLLS[!], and it's still a good choice. It has extensive customization available via code modification and/or RetroArch's runtime shader parameters.

 Many users don't care for the curvature effect and turn it off, like this:

This shader is available in Cg and Quark formats.

CRT-Easymode

This one was written by a fellow from the NeoGAF forums who goes by the name Easymode. It is notable for looking nice even at non-integer scale factors and for being very lightweight considering how nice it looks. It's a good one to try on mobile platforms and desktops/laptops with weaker GPUs. It also has some nice runtime parameters for switching between cgwg-style and Lottes-style mask effects.

This shader is available in Cg format only.

CRT-Hyllian

This one is written by Hyllian, who is well-known for his popular upscaling interpolation algorithm known as xBR. It includes some interesting options, such as a "blue boost" that is helpful for making water in many games go from purple to blue.

This shader is available in Cg format only.

CRT-Lottes

This one was written by Timothy Lottes, an engineer at Nvidia who is known for his work creating the FXAA fullscreen antialiasing GPU algorithm. This shader is adapted from the shadertoy he made and was generous enough to release into the public domain. Notably, it uses a sideways shadow mask effect that is designed to avoid chromatic aberration.

 It's easy to flatten this one out, as well, using RetroArch's runtime parameters to set the warpX/warpY values to zero or by commenting line 142 in the Quark shader:

This shader is available in Cg and Quark formats.

PhosphorLUT

This is one I worked on awhile back and it only focuses on doing a phosphor/shadow mask using an external lookup texture (LUT) and a little bit of horizontal blurring.

You can adjust the scale of the phosphor mask with 1.0 looking more like a high-res CRT monitor, while 1.5 and 2.0 look more like an SDTV or CGA monitor. As you adjust the scale, the colors can get wonky, so there are runtime parameters for dialing in the right balance. Here it is at a scale of 1.5:

 There's also a preset for use with 4K displays (not pictured here). This shader is available in Cg and Quark formats.

GTU

I've raved about this shader--which was written by aliaspider--before for its ability to blur out dithering, but it also belongs on any list of good CRT shaders. While it doesn't provide any phosphor/shadow mask effects, it does allow horizontal/vertical bandwidth control (for blending things like pseudo transparency and dithering), scanline effects and NTSC color blending/bleeding.

All of these effects are user-customizeable by editing the code (he put the various options right at the tops of the files for easy access) and, with the NTSC color option disabled, it looks remarkably close to the output of Micomsoft's famed XRGB-Mini Framemeister deinterlacing/upscaling device.

This shader is available in Cg and Quark formats.

CRT-Royale

This shader was written by a guy named TroggleMonkey and it uses some intense, RetroArch-specific black magic to overcome many of the issues with CRT emulation that I thought were unavoidable, particularly using large-scale blurring passes without totally wrecking performance and making a true RGB phosphor / shadow mask that looks good at less than 4K resolution. As I said, it is Cg-only and only works on RetroArch, at that (i.e., no OpenEmu, even though it supports Cg in general).

CRT-Royale has an option (on by default and in these shots) for simulating the characteristic glow of a CRT tube. This is another common goal of CRT shaders, and I've broken those off into their own group:

Glow/Halation

Glow

Written by Themaister, this one eschews phosphor/shadow mask effects and just focuses on using special blurs to accentuate the variable beam width of a CRT (i.e., brighter pixels bleed further into the space between scanlines).

 He also made a variant that tacks on his NTSC-composite shader (looks better in motion):

This shader is available in Cg format only.

CRT-Hyllian-Glow

Just like regular CRT-Hyllian, but with some whole-screen blur/glow.

This shader is available in Cg format only.

CRT-Lottes-Halation

Mr. Lottes made a revision to his scanline shadertoy that added a number of gaussian blur kernels to bloom out bright pixels, which increases the overall brightness of the image without getting the fullscreen haze of some of the other options.

Unfortunately, the limitations of the shadertoy format forced the blurs into a single pass, which is extremely slow. This variant is available in Cg format only.

For anyone who's curious, I took 4K screenshots of most of these, but blogspot down-rezzes them and adds jpeg compression on top of that, so I couldn't post those directly. Instead, here is a download.

CRT-Royale and 3dfx Shaders

Two fairly new shaders have popped up that are worth mentioning: TroggleMonkey's CRT-Royale and leilei's 3dfx. They're both available in Cg format in libretro's common-shaders github repo, though CRT-Royale utilizes some advanced features that aren't available in RetroArch v1.0.0.2 (the most recent release at the time of this writing).

CRT-Royale is particularly exciting for me because TroggleMonkey managed to overcome some issues with shadow-mask emulation that I thought were totally intractable at current common resolutions (i.e., 1080p). The result is some really great phosphor emulation at reasonable scale factors, along with all of the bells and whistles users have come to expect from CRT shaders, including "halation"/glow, bob-deinterlacing support and curvature, along with a ton of options that are unique to this shader.

I'm not going to cover many of them here because it would take forever to get screenshots and there's not much point when TroggleMonkey has included a very informative README with the code, along with support for RetroArch's new runtime parameter support (so you can see the effect of your changes in real-time). However, I thought the shadow mask stuff was super-cool and deserved some closeups. Here's a shot of the shader with default settings (as always, click to embiggen):

First, we'll look at my favorite effect, the in-line shadow mask (called slot-mask in the code):

This is the same configuration I was shooting for with my PhosphorLUT shader, and you can see that the configuration of the phosphors has that familiar vertical, staggered orientation:

Next, we have the very similar aperture grille:

 

The main difference between this and the in-line slot mask is that it doesn't have the slight staggering (only really visible in the closeups and at super-huge resolutions). In closeup of the LUT, you can see that it just removes the crossbars between triads:

Last, we have the dot-triad shadow mask (called "shadow-mask-EDP" in the code), which was common on CRT computer monitors:

 As you can see, it looks very similar to the high-res shots I took of my Compaq CRT monitor (from my emulation/TV post). And here's the dot-triad blown up:

The other shader I wanted to show is leilei's 3dfx shader, which tries to mimic the effects of a 3dfx GPU, known for some distinctive dithering among other things. In addition to obvious applications like RetroArch's Quake core, Nintendo's N64 also used a GPU that was very similar to a 3dfx, which makes it appropriate for RA's Mupen64plus core. When run at low-ish internal resolutions and paired with RetroArch's per-texture 3-point filtering, you can get a pretty good approximation of what N64s looked like.

Here are some shots of the shader at 320x240 and 640x480 (i.e., native and double res, respectively):

Native res:

Double internal res:

 As you can see, the doubled res looks significantly sharper, but the scanlines are thinner and less pronounced (and twice as many of them) relative to the native res. I also like native res because it makes HUD/menu items look a little less "pasted-on":
Native res:

Doubled internal res: