GLSL n-rook anti-aliasing - based on the idea from http://mlab.uiah.fi/~kkallio/antialiasing/EdgeFlagAA.pdf

nrook_antialiasing.glsl

// n-rook anti-aliasing - based on the idea from http://mlab.uiah.fi/~kkallio/antialiasing/
// GLSL implementation by Benjamin 'BeRo' Rosseaux
// licensed under CC0 1.0 Universal (CC0 1.0) Public Domain Dedication ( http://creativecommons.org/publicdomain/zero/1.0/ )
#version 150
#define nrookSamples 8
uniform vec2 resolution;
vec4 realMainContent(vec2 p){
   vec4 c = vec4(0.); 
   // ...
   return c; 
}
void main(){	
#if nrookSamples == 2
  const float nrook[2] = float[2](1.0, 0.0);
  const float nrookInverseScale = 0.5;       
  #define antialiased     
#elif nrookSamples == 4
  const float nrook[4] = float[4](1.0, 3.0, 0.0, 2.0);
  const float nrookInverseScale = 0.25;       
  #define antialiased     
#elif nrookSamples == 8
  const float nrook[8] = float[8](5.0, 0.0, 3.0, 6.0, 1.0, 4.0, 7.0, 2.0);
  const float nrookInverseScale = 0.125;       
  #define antialiased     
#elif nrookSamples == 16
  const float nrook[16] = float[16](1.0, 8.0, 4.0, 15.0, 11.0, 2.0, 6.0, 14.0, 10.0, 3.0, 7.0, 12.0, 0.0, 9.0, 5.0, 13.0);
  const float nrookInverseScale = 0.0625;       
  #define antialiased     
#elif nrookSamples == 32
  const float nrook[32] = float[32](28.0, 13.0, 6.0, 23.0, 0.0, 17.0, 10.0, 27.0, 4.0, 21.0, 14.0, 31.0, 8.0, 25.0, 18.0, 3.0, 12.0, 29.0, 22.0, 7.0, 16.0, 1.0, 26.0, 11.0, 20.0, 5.0, 30.0, 15.0, 24.0, 9.0, 2.0, 19.0);
  const float nrookInverseScale = 0.03125;   
  #define antialiased     
#elif nrookSamples == 64
  const float nrook[64] = float[64](35.0, 41.0, 5.0, 20.0, 7.0, 25.0, 46.0, 60.0, 47.0, 61.0, 49.0, 15.0, 0.0, 10.0, 29.0, 1.0, 33.0, 6.0, 4.0, 18.0, 57.0, 40.0, 30.0, 24.0, 2.0, 8.0, 62.0, 44.0, 53.0, 63.0, 27.0, 31.0, 37.0, 26.0, 22.0, 51.0, 19.0, 38.0, 28.0, 32.0, 16.0, 9.0, 12.0, 52.0, 39.0, 48.0, 58.0, 59.0, 56.0, 54.0, 34.0, 13.0, 55.0, 3.0, 50.0, 42.0, 45.0, 21.0, 36.0, 23.0, 17.0, 11.0, 43.0, 14.0);
  const float nrookInverseScale = 0.015625;   
  #define antialiased     
#else
  #undef antialiased     
#endif
#ifdef antialiased
  vec4 c = vec4(0.);
  for(int i = 0; i < nrookSamples; i++){
    c += realMainContent(((gl_FragCoord.xy + ((vec2(nrook[i], float(i)) * nrookInverseScale) - vec2(0.5))) / resolution.xy));
  }	  
  gl_FragColor = c / float(nrookSamples);
#else
  gl_FragColor = realMainContent(gl_FragCoord.xy / resolution.xy);
#endif	
}

Great !
But I am somehow lost, what should we insert in the realMainContent function ?
Do you have a complete sample ?