/* 
 *  fluffy.sl
 *
 *  Displacement Shader to create slight fluffiness 
 *     for use in modeling duck
 *     especially for pasting on spheres and ellipsoids
 *     because it tapers the flufiness at the ends instead
 *     of bunching them.
 *
 *  M. Geroch
 *  TV Digital Lighting HW 5
 * Spring, 1996
 *
 */


#include "/usr/local/accad/shaders/rmannotes.sl" 


displacement
fluffy( 
       float Km = 0.02;
       float scrunch = 30;
       float ramp= 0.17;
       float Kmtex = 0.05;
       string texturename="";
       )
{
        float magnitude;
	float taper;
	float fuzz=0.14;


/* taper the regular displacement at the ends if desired */
	taper = pulse(ramp, 1-ramp+fuzz, fuzz, t);
 
/* main layer */
	magnitude = taper * noise(s*scrunch, t*scrunch);

/* get more displacement from texture map if desired */
/* Km and Kmtex modulate the height of the displacement */
	if (texturename != "")
	  {
	    magnitude += 2*(float texture(texturename, s, t));
	    P += Kmtex * magnitude * normalize(N);
	  }
	else
	  {
	    P += Km * magnitude * normalize(N);
	  }
	    
/* now recalculate the normal at the point */
        N = calculatenormal(P);
}