uniform float screenWidth;
uniform float screenHeight;
uniform sampler2D depthMap;
uniform sampler2D rotateMap;
uniform float zFar;
uniform float zNear;
uniform float radius;
uniform float attBias;
uniform float attScale;

void main(void){
   // With SSAO
   float   att   = 0.0;
    
   vec4	rndTable[8];
 
   rndTable[0] = vec4 ( -0.5, -0.5, -0.5, 0.0 );
   rndTable[1] = vec4 (  0.5, -0.5, -0.5, 0.0 );
   rndTable[2] = vec4 ( -0.5,  0.5, -0.5, 0.0 );
   rndTable[3] = vec4 (  0.5,  0.5, -0.5, 0.0 );
   rndTable[4] = vec4 ( -0.5, -0.5,  0.5, 0.0 );
   rndTable[5] = vec4 (  0.5, -0.5,  0.5, 0.0 );
   rndTable[6] = vec4 ( -0.5,  0.5,  0.5, 0.0 );
   rndTable[7] = vec4 (  0.5,  0.5,  0.5, 0.0 );

   float   zb    = texture2D ( depthMap, vec2(gl_FragCoord.x/screenWidth,  gl_FragCoord.y/screenHeight)).x;
   float   z     = zFar*zNear/(zb * (zFar - zNear) - zFar); 
   vec3    plane = 2.0 * texture2D ( rotateMap, vec2(gl_FragCoord.x/4.0,gl_FragCoord.y/4.0)).xyz - vec3 ( 1.0 );
   float mult = radius/z;
   
   vec2 texCoord = vec2(gl_FragCoord.x/screenWidth,  gl_FragCoord.y/screenHeight);
   for ( int isample = 0; isample < 8; isample++ )
   {
        //vec3    sample  = reflect   ( rndTable [isample].xyz, plane );
        vec3    sample  = rndTable [isample].xyz - 2.0  * dot(plane,rndTable [isample].xyz) * plane;
        float   zSample = texture2D ( depthMap, texCoord  + mult*sample.xy).x;

        zSample = zFar * zNear / (zSample * (zFar - zNear) - zFar );
        
        //if ( zSample - z > 0.1 )
            //continue;
            
        float   dz = max ( zSample - z, 0.0 ) * 30.0;
        
        att += 1.0 / ( 1.0 + dz*dz );
   }
    
   att = clamp ( (att / 8.0 + attBias) * attScale, 0.0, 1.0 );
   gl_FragColor = vec4(att,att,att,1.0);
}