First, we'll take a look at the waterpaint shader, which has an effect similar to smoothing filters, such as SuperSaI, but with a little extra fattening that gives it the appearance of a watercolor painting:
This looks great already, but text can sometimes get a bit hard to read and some details get flattened out, so he also made a version that includes light scanlines (both the standard horizontal scanlines, as well as faint vertical lines, as would be found in a phospher mask):
I think this version does a better job of maintaining fine details and really looks nice, especially on Zelda:LttP.
Next, he produced a beautiful (and easily customizable) resolution-agnostic scanline shader. In contrast with my own scanline shaders, Themaister's shader will work with any scale factor instead of having one hardcoded in. Here's how his default version looks without and with bilinear filtering (smooth video), respectively:
In addition to this default, I modified the settings to create medium and dark scanline settings, as well (each shown without and with bilinear filtering enabled, respectively):
You can download these shader's from my mediafire account. If you would like to modify the scaline shaders yourself, you can play around with these figures:
const float base_brightness = 0.95;const vec2 sine_comp = vec2(0.05, 0.15);