/*
 * 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  
 * 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_screen2 (float Ka = 1, Kd = 0.75, Ks = 0.4, roughness = 0.1;
	   color specularcolor = 1;
	   color screencolor = color(1, 0, 0);
	   float density = 0.25, frequency = 20, dimensions = 3;)
{
	float swidth, twidth;
	float d;
	normal Nf;
	vector V;
	color Ct;
	float astrip, bstrip;
	float apart;
	float bpart;
	float sum;
	float hcomp = density;
	float vcomp = density;

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

	swidth = max (abs(Du(s)*du) + abs(Dv(s)*dv), MINFILTERWIDTH) * frequency;
	twidth = max (abs(Du(t)*du) + abs(Dv(t)*dv), MINFILTERWIDTH) * frequency;

	Cs = screencolor;
	astrip = clamp(boxstep(.5-(hcomp+twidth),.5-hcomp,t)
			- boxstep(.5+hcomp, .5+(hcomp+twidth),t),0,1); 	
	bstrip = clamp(boxstep(.5-(vcomp+swidth),.5-vcomp,t)
			- boxstep(.5+vcomp, .5+(vcomp+swidth),t),0,1); 	
	sum = astrip + bstrip;

/*		
Let's just test this
	apart = mod(apart, 2);
	bpart = mod(bpart, 2);
	
	sum = 0;
	if (apart > 1) sum = sum + 1;
	if (bpart > 1) sum = sum + 1;
	if (sum < 1) Os = 0;
*/
	
	Nf = faceforward(normalize(N),I);
	V = -normalize(I);
	Oi = color(sum/2);
      Ci = Oi * ( Cs * (Ka*ambient() + Kd*diffuse(Nf)) + specularcolor * Ks*specular(Nf,V,roughness));

}