/************************************************************
 * file: rockcolor.sl
 * author: Peter Stuart
 * date: 11/16/2002
 * $Id: rockcolor.sl,v 1.4 2003/01/27 04:32:48 ophi Exp $
 * description: Accompanies the rockdisp shader.
 *
 * ---- surface parameters ----------
 * freq: number of cells along the s and t directions
 * twist: twists the voronoi regions along s and t. Good values
 *        depend on frequency.
 * seed: controls random parameters
 * tipcolor: color at the voronoi cell boundaries
 * sidecolor: color in the center of the cell
 ************************************************************/

#include "voronoi.sl"
#include "rmannotes.sl"

/* ---- macro to help seed random numbers ------
 * it serves two purposes:
 *  - allows easy searching to ensure non-repeating numbers
 *  - automatically uses seed
 */
#define RN(x) (seed+(x)+0.5)

surface rockcolor(float freq = 10;
		  float twist = 1;
		  float seed = 192;
		  color tipcolor = color(1,1,1);
		  color sidecolor = color(0,0,0);)
{
  color layer_color, layer_opac, surface_color;
  float dist, posx, posy;
  float factor = 0.5;
  vector Nn = normalize(N);

  surface_color = Cs;

  /******* voronoi layer **********/
  float ss = s + 0.1*snoise2(s*twist*5+RN(1452), t*twist*5+RN(1459));
  float tt = t + 0.1*snoise2(s*twist*5+RN(1552), t*twist*5+RN(1559));

  voronoi_f1_2d(ss, tt, freq, 1, dist, posx, posy);
  dist *= dist; /* use dist^2 to get rounded concavities */

  layer_color = blend(sidecolor, tipcolor, dist);
  layer_opac = smoothstep(0,1,dist);
  surface_color = blend(surface_color, layer_color, layer_opac);

  Ci = surface_color*diffuse(normalize(N));
}