I posted the .slangp and .slang here: github.com/matijaerceg/...

The "shadow mask" effect has little to do with how shadow masks actually work, it just swaps pixels around horizontally.

There's an auto-adjusting "number of scanlines rounding" feature which works well for 3d games and allows for scanlines to be a multiple of output resolution, lessening likelihood of moire or horizontal jailbars.

Concessions are made for the sake of image quality and brainfeel rather than accuracy. As mentioned the scanlines gaps are thinner in bright areas because a SDR digital display cannot compete with the amount of energy coming from a single scanline on a CRT.

This shader works very well to clean up super compressed youtube videos too! It's sort of a reverse-AA happening, since we know that in these high-resolution or bilinear scaled videos there are solid fat pixels underneath. This low quality video looks a lot better with the shader.

One thing I dislike about many ShaderGlass shaders is too many parameters. I've tried to edit mine down to just the essentials. The important setting to set is the 224/240p toggle, depending if you're playing SNES for example. The others have explanations.

Scanlines alone help 240p content, but CRTs add additional texture. Instead of trying to simulate a shadow mask, which I find messes up chroma/luma, I just refract subpixels horizontally so as to create mask-like noise without having to process and affect color, or simulate it with fake phosphors.

Per Tim Lottes' concept, the shader redestributes the energy found in the original 'fat' pixels into a thin scanline. But due to clipping at high values, on a digital display we compensate by thickening the scanline (called adaptive scanlines I think).

The goal was to recreating what happens in our PERCEPTION and MEMORY when viewing on a CRT, rather than trying to simulate the literal visuals, which is technically impossible on a digital display.

I've never seen a CRT shader I liked, so I made one (for ShaderGlass). It was inspired by Tim Lottes' "energy conservation" concept on shadertoys.
- No brightness loss!!!
- presets for 224/240p
- parameters
- defaults are good for 4k output.