perlin1.h

#ifndef PERLIN_H
#define PERLIN_H

#include "rtweekend.h"

class perlin {
    public:
	perlin() {
	    ranfloat = new double[point_count];
	    for (int i = 0; i < point_count; ++i) {
		ranfloat[i] = random_double();
	    }

	    perm_x = perlin_generate_perm();
	    perm_y = perlin_generate_perm();
	    perm_z = perlin_generate_perm();
	 }

	~perlin() {
	    delete[] ranfloat;
	    delete[] perm_x;
	    delete[] perm_y;
	    delete[] perm_z;
	}

	double noise(const point3& p) const {
	    auto i = static_cast<int>(4*p.x()) & 255;
	    auto j = static_cast<int>(4*p.y()) & 255;
	    auto k = static_cast<int>(4*p.z()) & 255;

	    return ranfloat[perm_x[i] ^ perm_y[j] ^ perm_z[k]];
	}

	private:
	    static const int point_count = 256;
	    double* ranfloat;
	    int* perm_x;
	    int* perm_y;
	    int* perm_z;

	    static int* perlin_generate_perm() {
		auto p = new int[point_count];

		for (int i = 0; i < perlin::point_count; i++) {
		    p[i] = i;
		}

		permute(p, point_count);

		return p;

	    }

	    static void permute(int* p, int n) {
		for (int i = n-1; i > 0; i--) {
		    int target = random_int(0, i);
		    int tmp = p[i];
		    p[i] = p[target];
		    p[target] = tmp;
		}
	    }
};

#endif