// gray offset
  // (c) 2005 Holger Grahn 
  float time=0;
  float sampleDist = 1.0f/512.0f;  // distance one pixel in u/v
  
  float displaceAmount=0.2;
  
  sampler2D image : register(s0);
  
  float4 main(
          float4 Pos : POSITION,
          float2 texCoord: TEXCOORD0) : COLOR 
  {
          float4 img = tex2D(image, texCoord);
  
          // convert to gray 
          float2 sum;
          sum.x = dot(img, float4(0.90f, 0.4, 0.2f, 0.0f))-0.5;
          sum.y = dot(img, float4(0.2f, 0.4f, 0.9f, 1.0f))-0.5;
          float fac=displaceAmount;
          //fac *= pow(sin(time*3.1414)-0.5,1.7);
          fac *= pow(time,1.7);
          //img = tex2D(image, float2(texCoord.x+exp(fac*sum.x),texCoord.y+fac*sum.y));
          img = tex2D(image, float2(texCoord.x+(fac*sum.x),texCoord.y+fac*sum.y));
          return img;
  }