/****************************************************************************
 * based on woodblockprint (info below), but modified to show
 * different features
 * 
 ************************************************
 * 
 * The original shader was:
 *
 * woodblockprint.sl -- surface shader for carved wood block printing
 *
 * (c) Copyright 1998 by Fleeting Image Animation, Inc.
 * All rights reserved.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and for any purpose, provided that the above copyright
 * notice appear in all copies of this software.
 *
 * Author: Scott F. Johnston
 *
 * Reference:
 *   _Advanced RenderMan: Creating CGI for Motion Picture_, 
 *   by Anthony A. Apodaca and Larry Gritz, Morgan Kaufmann, 1999.
 *
 ****************************************************************************/


surface
woodblockprint ( float freq = 2; float duty = 0.50;
		 color stripe_color = 0;)
{
    float sawtooth = mod(u * freq, 1);
    float triangle = abs(2.0 * sawtooth - 1.0);
    float square = filterstep(duty, triangle);

    Ci = mix(Cs, stripe_color, square);
}