// identity 
float time=0;
float sampleDist = 1.0f/512.0f;  // distance one pixel in u/v

float grayLevel = 0.075;

sampler2D image : register(s0);


float4 main(
	float4 Pos : POSITION,
	float2 texCoord: TEXCOORD0) : COLOR 
{
	float4 img = tex2D(image, texCoord);

	// convert to gray 
	float gray = dot(img, float4(0.30f, 0.59f, 0.11f, 0.0f));
	
	if (gray <=grayLevel)
		img.a = 0; // img.a * pow(gray/grayLevel,2);

	
	return img;
}