/*
surface shader:
	spinningblade.sl

creator:
	Nick Meshes, DePaul University

description:
	If this baby works, it will produce a look like that of a helicopter blade in motion.

Parameters:
	float Ka, Kd, Ks, roughness:			familiar old friends
	color specularcolor:				
	float hmin, hmax, wmin, wmax:			the standard min-max box
	float slope:					slope of the blade
	float bladelength:				length of the blade
	float orientate:					x(0), y(1), or z(2) - sorry, it's orthogonal fer now
	float bladewidth:					width of the blade
	float bladedepth:					how deep do you want to go
	float clock:					(1) clockwise or (0) counter-clockwise
	float blurmargin:					slope of the farthest line of blurring
*/

surface spinningblade(
	float Ka = 1, Kd = 0.75, Ks = 0.4, roughness = 0.1;
	color specularcolor = 1;
	float slope = 0;
	float bladelength = 3;
	float bladedepth = 1;
	float orientate = 0;
	float bladewidth = 1;
	float clock = 1;
	float blurmargin = 0;
){
	normal Nf;
	vector V;
	point cent, curr, len;
	float zcoord;

	setxcomp(cent, (wmin + wmax)/2);
	setycomp(cent, (hmin + hmax)/2);
	setzcomp(cent, 0);
	
	if (orientate == 0){
		setxcomp(curr, ycomp(P));
		setycomp(curr, zcomp(P));
		zcoord = xcomp(P);
	}
	else if (orientate == 1){
		setxcomp(curr, xcomp(P));
		setycomp(curr, zcomp(P));
		zcoord = ycomp(P);
	}
	else{
		setxcomp(curr, xcomp(P));
		setycomp(curr, ycomp(P));
		zcoord = zcomp(P);
	}
	setzcomp(curr, 0);
	
	len = cent - curr;
	if (length(len) > bladelength)
		Oi = 0;
	else if (abs(zcoord) > bladedepth)
		Oi = 0;
	else
	{
		float Tslope = -(slope/2);
		Tslope = slope - Tslope;
		float A = xcomp(cent) - xcomp(curr);
		A = A/Tslope;
		float B = ycomp(cent) - ycomp(curr);
		B = B/Tslope;

		point ST;
		setxcomp(ST, xcomp(cent) + (A * slope));
		setycomp(ST, ycomp(cent) + (B * slope));
		len = ST - curr;
		if (length(len) <= bladewidth)
			Oi = 1;
		else Oi = .2;
	}
	Nf = faceforward(normalize(N),I);
	V = -normalize(I);
	Ci = Oi * ( Cs * (Ka*ambient() + Kd*diffuse(Nf)) + specularcolor * Ks*specular(Nf,V,roughness));	
}