Texture Mapping & Edge Detection

Image with Edge Detection and Aliased (Zoom)
The popping is very noticeable here, especially in the finer details of the image.

Original Image (Background painting by Dutch artist Pieter Claesz, 1624.)	With Edge Detection Sampling 2 Neighboring Pixels
	When only 2 neighboring pixels are sampled the edge is noticeably dimensional and we loose part of the edge.
With Edge Detection Sampling 8 Surrounding Pixels	With Edge Detection Sampling 8 Surrounding Pixels
With 8 sampled surrounding pixels the edge is better defined.

Code

/* simple shader for use in finding 
the edge for a texture map */
surface
edge_mapper(	float	Kd = 1,
	s_offset = .005,
	t_offset = .005,
	sensitivity = .1,
	blur =.02,
	mixValue = .3,
	mixValue2 = .3,
	sampleRate = 1,
	lightness = 1;
	string	texname = "")	/*texture to apply to 
object*/
{
color	edgeDetect = color(1, 1, 1);
color	surfcolor = color(1, 1, 1);
float total = 0;
float 	c1, c2, i, j, diff;

/*	Use the texture function if user specifies
 a texture file*/
if(texname != "") {
	color textureMap = texture(texname,s,t)
 * lightness;
	c1 = float texture(texname, s, t);

	/*	Grab a surrounding sampling of pixels */
	for(i = -sampleRate; i <= sampleRate;
 i = i + 1)
	{
		for(j = -sampleRate; j <= sampleRate;
 j = j + 1)
		{
	 	c2 = float texture(texname, s + 
(i*s_offset), t + (j*t_offset));
		diff = abs(c1-c2);
		total += diff;
		}
	}


/*surfcolor =  smoothstep(-blur, blur, 1 - 
sqrt(total) - sensitivity);*/
edgeDetect = 1 - smoothstep(-blur, blur, 1 - 
sqrt(total) - sensitivity);

/*	Mix the edge with the original image*/
surfcolor = mix(edgeDetect,textureMap,mixValue);
}



normal	n = normalize(N);
normal	nf = faceforward(n, I);

/*	*/
Oi = Os;


color	diffusecolor = Kd * diffuse(nf);


Ci = Oi * Cs * surfcolor * diffusecolor;
}