source: data/data_extern/programs/Cg/ASCIIFP.cg

sampler2D RT : register(s0);
sampler3D pattern : register(s1);

float4 ASCII_ps( float4 pos : POSITION,
      float2 TexCoord : TEXCOORD0,
                        uniform float2 numTiles,
                        uniform float2 iNumTiles,
                        uniform float2 iNumTiles2,
                        uniform float4 lum,
                        uniform float charBias) : COLOR
{
    float3 local;

        //sample RT
        local.xy = fmod(TexCoord, iNumTiles);
        float2 middle = TexCoord - local.xy;
        local.xy = local.xy * numTiles;
        
        //iNumTiles2 = iNumTiles / 2
        middle = middle + iNumTiles2;
        float4 c = tex2D(RT, middle );
        
        //multiply luminance by charbias , beacause not all slices of the ascii
        //volume texture are used
        local.z = dot(c , lum)*charBias;
        
        //fix to brighten the dark pixels with small characters
        //c *= lerp(2.0,1.0, local.z);
        
        c *= tex3D(pattern,local);
        return c;
}