surface
anaPlastic(float	Ka = 1,			/* ambient brightness */
					Kd = 0.5,		/* basic brightness */
					Ks = 0.7,		/* hilite brightness */
					roughness = 0.1;/* hilite spread */
vector 	hilitecolor = 1	/* hilite color */ )
{
vector	i;
vector	ambientcolor, diffusecolor, speccolor,
		surfcolor = 1, surfopac = Of;

/* STEP 1 - make a copy of the surface normal one unit in length */
vector	n = normalize(N);
vector	nf = frontface(n, I);

/* STEP 2 - set the apparent surface opacity */
Of = surfopac;

/* STEP 3 - calculate the lighting components */
ambientcolor = Ka * ambient();
diffusecolor = Kd * diffuse(nf);
i = normalize(-I);
speccolor = Ks * specular(nf, i, roughness) * hilitecolor;
vector c1= set (1, 0, 0); vector c2=set (0, 1, 0.2);
float ds;
vector result;
float side=1, freq=50, amplitude=2 ;
		float d=(1-side)*3*s+side*3*t;
	//	ds=amplitude/5*(sq*(step(0,sin(d*freq))-0.5)+(1-sq)*(sin(d*freq)))+0.5;
		ds=amplitude/5*sin(d*freq);
		if (((1-side)*t+side*s)<ds)	
			result=set(c1);
			
		else
			result=set(c2);


/* STEP 4 - calculate the apparent surface color */
Cf = Of * result * surfcolor * (ambientcolor + diffusecolor + speccolor);
}