surface
lowell_spline(float	Kd = 1,
			        linepoint = 0.3,
			 	    lineramp  = 0.01;
			 color  basecol   = (0,0,0),
					midcol1   = (1,0,0),
					midcol2   = (0,1,0),
					midcol3   = (0,0,1),
					midcol4   = (0,1,0),
					midcol5   = (1,1,1),
					midcol6   = (0,0,0),
					topcol    = (1,0,0),
					white     = (1,1,1))
{
color	surfcolor = 1;

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

float humpdis = 0;

if(displacement("hump", humpdis) == 1)
	{
	surfcolor = spline(humpdis,white,basecol,midcol1,midcol2,midcol3,midcol4,midcol5,midcol6,topcol,white);
	}
Oi = Os;

color	diffusecolor = Kd * diffuse(nf);
Ci = Oi * Cs * surfcolor * diffusecolor;
}