/* Displacement shader "hills"
 * Final Assignment: use of noise
 *   Tom Suchan
 * This is a simple but verstile displacement shader good for beach parties,
 * moon walks, or where ever an uneven surface is needed. The shader is
 * intended to create a hilly surface. The user can control the amount
 * of displacement with Km and the "hill" (frequancy) parameter.
 */ 
#include "rmannotes.sl"

displacement hills(float Km = 0.4; float hill = 4)
{
   float magnitude = 0, layer_mag;
   point PP;
  
   PP = transform("shader", P); /*change space */

   layer_mag = noise(PP * hill); /* add noise to create bumbs */
   magnitude += layer_mag;
   
   /* output */
   P += -Km * magnitude * normalize(N);
   N = calculatenormal(P);
}