sampler RT : register(s0);

float4 Tiling_ps(float4 inPos : POSITION,
				float2 iTexCoord : TEXCOORD0,
				uniform half NumTiles,
				uniform half Threshhold) : COLOR
{


	half3 EdgeColor = {0.7, 0.7, 0.7};

    half size = 1.0/NumTiles;
    half2 Pbase = iTexCoord - fmod(iTexCoord, size.xx);
    half2 PCenter = Pbase + (size/2.0).xx;
    half2 st = (iTexCoord - Pbase)/size;
    half4 c1 = (half4)0;
    half4 c2 = (half4)0;
    half4 invOff = half4((1-EdgeColor),1);
    if (st.x > st.y) { c1 = invOff; }
    half threshholdB =  1.0 - Threshhold;
    if (st.x > threshholdB) { c2 = c1; }
    if (st.y > threshholdB) { c2 = c1; }
    half4 cBottom = c2;
    c1 = (half4)0;
    c2 = (half4)0;
    if (st.x > st.y) { c1 = invOff; }
    if (st.x < Threshhold) { c2 = c1; }
    if (st.y < Threshhold) { c2 = c1; }
    half4 cTop = c2;
    half4 tileColor = tex2D(RT, PCenter);
    half4 result = tileColor + cTop - cBottom;
    return result;
}