Custom Voronoi Shader

//Custom Voronoi shader
//I've divided the image into blocks where each block contains a point
//every point's offset from the block's corner is stored in PointsSampler(a noisy texture)
float2 BlockSize : register(C0);
float2 BlockOffset : register(C1);
float2 pSize : register(C2);
sampler2D ImageSampler : register(S0);
sampler2D PointsSampler : register(S1);

float4 main(float2 uv : TEXCOORD) : COLOR
{
	//get coresponding point from noisy texture
	//convert uv from [0,1] to actual pixels
	float bx = floor((uv.x * pSize.x - BlockOffset.x) / BlockSize.x);
	float by = floor((uv.y * pSize.y - BlockOffset.y) / BlockSize.y);
	float cx = pSize.x * uv.x;
	float cy = pSize.y * uv.y;

	float2 centerOfBrick;

	float2 bSize = float2(floor(pSize.x / BlockSize.x), floor(pSize.x / BlockSize.x));

	//Here I find the closest point and how far away it is(cell1, dist1)
	//and  the second closest point(cell2, point2)
	float dist1 = 10 * BlockSize.x, dist2, dist;
	float4 coords;
	float dx, dy;
	float2 cell1 = float2(bx,by), cell2;

	for(int y = -1; y < 2; y++)
		for(int x = -1; x < 2; x++)
		{
			if(bx + x >= 0 && by + y >= 0 && bx + x < bSize.x && by + y < bSize.y)
			{
				coords = tex2D(PointsSampler, float2((bx + x)/bSize.x,(by + y)/bSize.y));
				dx = coords.r * 255 + (bx + x) * BlockSize.x + BlockOffset.x - cx;
				dy = coords.g * 255 + (by + y) * BlockSize.y + BlockOffset.y - cy;
				dist = sqrt(dx*dx + dy*dy);

				if(dist < dist1)
				{
					dist2 = dist1;
					cell2 = cell1;

					dist1 = dist;
					cell1 = float2(bx + x, by + y);
				}
			}
		}

	// You may ignore this following part
	//pixelated color
	centerOfBrick.x = (0.5f + cell1.x) * BlockSize.x + BlockOffset.x;
	centerOfBrick.x /= pSize.x;
	centerOfBrick.y = (0.5f + cell1.y) * BlockSize.y + BlockOffset.y;
	centerOfBrick.y /= pSize.y;
	float4 imgcolor = tex2D(ImageSampler, centerOfBrick);

	imgcolor.r = 0;
	imgcolor.g = 0;
	imgcolor.b = 0;

	imgcolor.r = 1 - (dist1) / 5;

	//this line somehow clears the red value for some pixels
	imgcolor.g = 1 - min(1,max(0,dist2)); //clip dist2 to [0,1]

	imgcolor.a = 1;



	return imgcolor;//rgba
}


technique Tech
{
	pass Pss
	{
		pixelshader = compile ps_3_0 main();
	}
}