surface
test_surf(float	Kd = 1,
			        linepoint = 0.5,
			 	    lineramp  = 0.5;
			 color  basecol   = (1,1,1),
			 		topcol    = (1,0,0))
{
color	surfcolor = 1;

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

float humpdis = 0;

if(displacement("hump", humpdis) == 1)
	{
	float ramp = smoothstep(linepoint - lineramp, linepoint + lineramp, humpdis);
	surfcolor = mix(basecol, topcol, ramp);
	}
Oi = Os;

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