SSAO woes

float4x4 matWorldViewProjection;

struct VS_INPUT 
{
   float4 Position: POSITION0;
};

struct VS_OUTPUT 
{
   float4 Position: POSITION0;
   float4 Pos : TEXCOORD0;
};

VS_OUTPUT vs_main(VS_INPUT Input)
{
   VS_OUTPUT Output;
   Output.Position = mul(Input.Position, matWorldViewProjection);
   Output.Pos = Output.Position;
   
   return Output;
}

struct PS_INPUT 
{
   float4 Pos : TEXCOORD0;  
};

float4 ps_main(PS_INPUT Input) : COLOR0
{
   float depth = Input.Pos.z / Input.Pos.w;
   return float4(depth, 1.0f, 1.0f, 1.0f);
}

struct VS_INPUT 
{
   float4 Position : POSITION0;
};

struct VS_OUTPUT 
{
   float4 Position : POSITION;   
   float2 TexCoord : TEXCOORD0;
   float4 Pos : TEXCOORD1; 
};

VS_OUTPUT vs_main(VS_INPUT Input)
{
   VS_OUTPUT Output;

   Output.Position = float4(sign(Input.Position.xy), 0.0, 1.0);
   Output.TexCoord.x = (Output.Position.x + 1.0) * 0.5;
   Output.TexCoord.y = 1.0 - ((Output.Position.y + 1.0) * 0.5);
   Output.Pos = Output.Position;
    
   return Output;
}

sampler2D DepthTexture;
sampler2D RandomTexture;

float4x4 matProjectionInverse;

float fRange;
int nNumSamples;
float2 fRandTextureSize;

struct PS_INPUT 
{
   float2 TexCoord : TEXCOORD0;
   float4 Pos : TEXCOORD1; 
};

float4 ps_main(PS_INPUT Input) : COLOR0
{   
   float4 samples[16] =
   {
      float4(0.355512, -0.709318, -0.102371, 0.0),
      float4(0.534186, 0.71511, -0.115167, 0.0),
      float4(-0.87866, 0.157139, -0.115167, 0.0),
      float4(0.140679, -0.475516, -0.0639818, 0.0),
      float4(-0.0796121, 0.158842, -0.677075, 0.0),
      float4(-0.0759516, -0.101676, -0.483625, 0.0),
      float4(0.12493, -0.0223423, -0.483625, 0.0),
      float4(-0.0720074, 0.243395, -0.967251, 0.0),
      float4(-0.207641, 0.414286, 0.187755, 0.0),
      float4(-0.277332, -0.371262, 0.187755, 0.0),
      float4(0.63864, -0.114214, 0.262857, 0.0),
      float4(-0.184051, 0.622119, 0.262857, 0.0),
      float4(0.110007, -0.219486, 0.435574, 0.0),
      float4(0.235085, 0.314707, 0.696918, 0.0),
      float4(-0.290012, 0.0518654, 0.522688, 0.0),
      float4(0.0975089, -0.329594, 0.609803, 0.0)
   };
           
   float depth = tex2D(DepthTexture, Input.TexCoord).r;
   float4 eyePos = mul(float4(Input.Pos.x, Input.Pos.y, depth, 1.0f), matProjectionInverse);
   eyePos.xyz = eyePos.xyz / eyePos.www;
   eyePos.w = 1.0f;   

   float4 randomPlane = tex2D(RandomTexture, Input.Pos.xy * fRandTextureSize.xy);
   randomPlane = randomPlane * 2.0 - float4(1.0, 1.0, 1.0, 1.0);

   float occlusion = 0.0;
   for (int i = 0; i < nNumSamples; i++)
   {
      float3 sample = eyePos + fRange * reflect(samples.xyz, randomPlane.xyz);
   
      float3 ss = sample.xyz * float3(0.75, 1.0, 1.0);
      float4 sz = tex2Dproj(DepthTexture, float4(ss * 0.5 + ss.z * float3(0.5, 0.5, 0.5), 1.0));

      float zDifference = 50.0 * max(sample.z - sz.x, 0.0);
      occlusion += 1.0 / (1.0 + zDifference * zDifference);
   }
   return float4(occlusion / nNumSamples, occlusion / nNumSamples, occlusion / nNumSamples, occlusion / nNumSamples);
}