/*
 * nick_screen
 *
 * DESCRIPTION:
 *   Makes a surface that looks like a metal screen.  Strips of metal run
 *   parallel to lines of two dimensions.  You can adjust the Ka, Kd, Ks, etc.
 *   to change the material appearance.  This texture antialiases pretty
 *   well, even with only one sample per pixel.
 *
 * PARAMETERS:
 *   Ka, Kd, Ks, roughness, specularcolor - work just like the plastic shader
 *   frequency - how many cycles of screen in st space
 *   density - how much of each cycle is opaque?
 *   dimensions - x = 1, y = 2, z = 4, add the two you want
 *                i.e x+y = 3, x+z = 5, y+z = 6  
 *	widthoffset will be between 0 and (windowwidth + wallwidth)
 *	heightoffset will be between 0 and (windowheight + wallheight)  
 *
 * 
 * AUTHOR: Nick Meshes
 *
 *
 *
 * The RenderMan (R) Interface Procedures and RIB Protocol are:
 *     Copyright 1988, 1989, Pixar.  All rights reserved.
 * RenderMan (R) is a registered trademark of Pixar.
 */



#define boxstep(a,b,x) (clamp(((x)-(a))/((b)-(a)),0,1))
#define MINFILTERWIDTH 1.0e-7



surface
nick_screen (float Ka = 1, Kd = 0.75, Ks = 0.4, roughness = 0.1;
	   color specularcolor = 1;
	   color screencolor = color(1, 0, 0);
	   float dimensions = 3;
	   float windowwidth = 1, wallwidth = 1;
	   float windowheight = 1, wallheight = 1;
	   float widthoffset = 0, heightoffset = 0;
 )
{
	normal Nf;
	vector V;
	float apart;
	float bpart;
	float sum;

	if (dimensions == 5){
		apart = abs(xcomp(P));
		bpart = abs(zcomp(P));
	}
	else if (dimensions == 6){
		apart = abs(ycomp(P));
		bpart = abs(zcomp(P));
	}
	else{
		apart = abs(xcomp(P));
		bpart = abs(ycomp(P));
	}

	Cs = screencolor;
	apart = mod((apart + widthoffset), (windowwidth + wallwidth));
	bpart = mod((bpart + heightoffset), (windowheight + wallheight));
	
	sum = 0;
	if (apart > (wallwidth/2))
		if (apart < (windowwidth + (wallwidth/2))) sum = sum + 1;
	if (bpart > (wallheight/2))
		if (bpart < (windowheight + (wallheight/2))) sum = sum + 1;
	
	if (sum == 2) Os = 0;

	Nf = faceforward(normalize(N),I);
	V = -normalize(I);
	Oi = Os;
      Ci = Oi * ( Cs * (Ka*ambient() + Kd*diffuse(Nf)) + specularcolor * Ks*specular(Nf,V,roughness));

}