Old School Super FX Shader

Has anyone tried to reproduce 3d shaders on older hardware such as the Super FX Chip produced similar to Vortex and Star Fox?
It is very easy to get the faceted look, but I can't think of a decent way to get the classic dithering effect.
One idea I had would be to over lay the rendered mesh with a static dithered grid. Has anyone tried anything similar? It would be cool to see something like this especially if it was compatible with iOS/Android.

 

I thought I'd give it a try and this is what I got as a result:

Webplayer
It looks ok, but the shader seems too complex for what it is actually doing and I doubt it would run on iOS due to the fact it is a surface shader. It uses a ramp like toon shading and is also affected by lights. Any ideas on how to make this more vertex based and how to remove the dithering if it is bright enough?

Code (csharp):

1.  Shader "SuperFX/Default" {
2.     Properties {
3.       _MainTex ("Texture", 2D) = "white" {}
4.       _Ramp ("Shading Ramp", 2D) = "gray" {}
5.       _Detail ("Detail", 2D) = "gray" {}
6.     }
7.     SubShader {
8.       Tags { "RenderType" = "Opaque" }
9.       CGPROGRAM
10.       #pragma surface surf Ramp
11.  
12.       sampler2D _Ramp;
13.  
14.       half4 LightingRamp (SurfaceOutput s, half3 lightDir, half atten) {
15.           half NdotL = dot (s.Normal, lightDir);
16.           half diff = NdotL * 0.5 + 0.5;
17.           half3 ramp = tex2D (_Ramp, float2(diff)).rgb;
18.           half4 c;
19.           c.rgb = s.Albedo * _LightColor0.rgb * ramp * (atten * 2);
20.           c.a = s.Alpha;
21.           return c;
22.       }
23.  
24.       struct Input {
25.           float2 uv_MainTex;
26.           float4 screenPos;
27.       };
28.       sampler2D _MainTex;
29.       sampler2D _Detail;
30.        
31.       void surf (Input IN, inout SurfaceOutput o) {
32.          
33.           float2 screenUV = (IN.screenPos.xy) / (IN.screenPos.w);
34.           screenUV *= float2(12*5,8*5);
35.           o.Albedo = tex2D (_Detail, screenUV).rgb * 1;
36.           o.Albedo *= tex2D (_MainTex, IN.uv_MainTex).rgb;
37.       }
38.       ENDCG
39.     }
40.     Fallback "Diffuse"
41.   }

 

What were you using as a ramp texture for this? Also, it compiles with errors in Unity 4, anyone know why?

 

Theres a way? to open this Shader on Unity 5.6.0f3 (32-bit) Personal Editon?