Blackops - Better SSAO

uniform sampler2D sampler0;
uniform sampler2D sampler1;
uniform sampler2D sampler2;

uniform float displayWidth;
uniform float displayHeight;
uniform float aspectRatio;
uniform float near;
uniform float far;

float readDepth( vec2 coord );

void main(void)
{
   float depth = readDepth( gl_TexCoord[0].st );
   float d;

   float pw = 1.0 / displayWidth;
   float ph = 1.0 / displayHeight;

   float aoCap = 1.0;
   float ao = 0.0;
   float aoMultiplier=250.0;
   float depthTolerance = 0.01;

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   pw*=2.0;
   ph*=2.0;
   aoMultiplier/=2.0;

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   pw*=2.0;
   ph*=2.0;
   aoMultiplier/=2.0;

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   pw*=2.0;
   ph*=2.0;
   aoMultiplier/=2.0;

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y+ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x+pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   d=readDepth( vec2(gl_TexCoord[0].x-pw,gl_TexCoord[0].y-ph));
   ao+=min(aoCap,max(0.0,depth-d-depthTolerance) * aoMultiplier);

   ao/=16.0;

   gl_FragColor = vec4(1.0-ao) * texture2D( sampler0, gl_TexCoord[0].st );
}

float readDepth( vec2 coord ) {
   float depth = texture2D( sampler1, coord ).x;
   float depth2 = texture2D( sampler2, coord ).x;
   if ( depth2 < 1.0 ) {
      depth = depth2;
   }
    depth = 2.0 * near * far / ( far + near - ( 2.0 * depth - 1.0 ) * ( far - near ) );
    return depth;
}