surface facehair (string spacename = "shader",
                         ribname = "";
                 float  Kn = 0.1,
						Kf = 8,
                        len = 0.4,
                        basewidth = 0.006,
						tipwidth = 0.0001,
						density = 0.5,
						neglen = .5)
{
normal n = normalize(N);

color surfcolor = Cs;    
if(random() > density && ribname != "")
    {
    normal nn = normalize(ntransform(spacename, N));

	// Used to bias the hair in the 'u' direction
	vector uBias = normalize(transform(spacename, dPdu));
	vector vBias = normalize(transform(spacename, dPdv));
	vector bias = vector( (uBias[0] + vBias[0])/2,
						  (uBias[1] + vBias[1])/2,
						  (uBias[2] + vBias[2])/2);
	
    point  base = transform(spacename, P);
    point  tip = base + nn * len;

	// Wiggle the mid point
	float  ns = noise(transform(spacename, P) * Kf);
	ns = ns - 0.5;
	ns = ns * Kn;	
	point  mid = base + (nn * len)/3 + ns;

	// Handy to see where the hairs are placed
    surfcolor = color(1,0,0);

	// Generate the rib file containing the curves (aka hairs)
    facehair(ribname,  base,  mid + bias/3, tip + bias,  basewidth, tipwidth);
    }
Oi = Os;
Ci = Cs * Oi * surfcolor;
}