float3 LensDistortionPass(float2 tex){
	// lens distortion coefficient (between
	float k = -0.15;

	// cubic distortion value
	float kcube = 0.5;

	float r2 = (tex.x-0.5) * (tex.x-0.5) + (tex.y-0.5) * (tex.y-0.5);
	float f = 0.0;

	//only compute the cubic distortion if necessary
	if (kcube == 0.0){
		f = 1 + r2 * k;
	}
	else {
		f = 1 + r2 * (k + kcube * sqrt(r2));
	};

	// get the right pixel for the current position
	float x = f*(tex.x-0.5)+0.5;
	float y = f*(tex.y-0.5)+0.5;
	float3 inputDistord = tex2D(tDiffuse,float2(x,y)).rgb;

	return inputDistord;
}

float3 LensDistortionShader(float4 position : SV_Position, float2 texcoord : TEXCOORD0) : SV_Target {
	float3 color = LensDistortionPass(texcoord).rgb;

	return color.rgb;
}