#include "rmannotes.sl"

/*
 * perturbed_noise(): 
 */

surface
perturbed_noise(float octaves		= 6,
			lacunarity	= 2,
			nscale		= 3,
			pscale		= 6,
			brightness	= 0,
			contrast	= 1,
			distort		= 1,
			ratio		= 0.5;
		float 	Ks		= 0.4, 
			Kd		= 0.6, 
			Ka		= 0.1, 
			roughness	= 0.1; 
		color 	specular_color	= 1.0;
		string	texmap		= "" )
{

	float i, size;
	vector perturb;
	color noisecolor;
	point Psh;

    	normal Nf;
    	vector V;

    	Nf = faceforward( normalize(N), I );
    	V = -normalize(I);

    	
    	noisecolor	= 0.0;
    	perturb		= 0.0;
 
    	
    	size = pscale;
	Psh = point(s*size, t*size, 0);
    	
    	for (i=0; i < octaves; i+=1)
    	{
    		perturb += (( vector noise(s*size, t*size)-0.5 ) * 2.0) / size;
    		size *= lacunarity;
    	}
	perturb = ((perturb + (brightness - 0.5)) * contrast) + 0.5;


    	size = nscale;
	Psh = point(s*size, t*size, 0);
    	Psh += perturb * distort;
    	for (i=0; i < octaves; i+=1)
    	{
    		noisecolor += (( color noise(xcomp(Psh)*size, ycomp(Psh)*size)-0.5 ) * 2.0) / size;
    		size *= lacunarity;
    	}
	noisecolor = ((noisecolor + (brightness - 0.5)) * contrast) + 0.5;

    	Ci = ratio * noisecolor + (1.0-ratio)*Cs;
    	Ci = Ci * (Ka*ambient() + Kd*diffuse(Nf))
    		+ Ks*specular_color*specular(Nf, V, roughness);
}