displacement legodot (float dotradius = 0.3,
                        height = 0.2,
                        dotSfrequency = 1, /* how many dots this way */
                        dotTfrequency = 1; /* how many dots that way */
                 )
{
	float magnitude,
              smod = mod(s*dotSfrequency, 1),
	      tmod = mod(t*dotTfrequency, 1);

	/* dot shall be centered at (0.5,0.5) in [0,1]X[0,1] */

	if (sqrt((smod-0.5)*(smod-0.5)+(tmod-0.5)*(tmod-0.5)) <= dotradius)
		magnitude = height;
	else
		magnitude = 0;

	 P = P + (normalize(N) * magnitude);
         N=calculatenormal(P);
}