// identity 
  float time=0;
  float sampleDist = 1.0f/512.0f;  // distance one pixel in u/v
  
  sampler2D image : register(s0);
  
  float4 main(
          float4 Pos : POSITION,
          float2 texCoord: TEXCOORD0) : COLOR 
  {
          float4 img = tex2D(image, texCoord);
  
          // convert to gray 
          float4 sum = dot(img, float4(0.30f, 0.59f, 0.11f, 0.0f));
          
          sum.a=img.a; // keep alpha
          return lerp(img,sum,time);         
  }