I've added a shader in this pack that should be what you're looking for: https://pixel-boy.itch.io/patternmix, for the pixelated rendering, I use a SubViewport in the demo, but I have also includes the pixelation option in the shader.
Alternatively, I found this one which looks quite similar but without the pixelation effect: https://godotshaders.com/shader/sine-morphing/