So, for my 90s/vintage CGI aesthetic video game I'm working on again I'm trying to make screen dithering in Godot since it was heavilyused to compress renders back then. I wanted to do error diffusion dithering (source 1) because that's what most early renders used back then, however, it's pretty much impossible in Godot's shader language since you need both RGB and XY values of a pixel (something Godot doesn't support), the next best thing is noise dithering (source 2) specifically blue noise dithering. My first attempt is god awful and my next attempt (which is the images supplied). aren't terrible but still not great. I DO NOT WANT ORDERED DITHERING (source 3). So, If anyone has a solution on how to do it, please tell me. Feedback on my current shader is also appreciated.

Regards Mediocre Metastasis.

Source 1:                                             Source 2:                                              Source 3:

My shader:

After pixelating it, it doesn't look that bad.