// Code from http://www.flipcode.com/archives/Perlin_Noise_Class.shtml
// This is only in PolyVox for the purpose of the examples. It was not written by
// the PolyVox authors and cannot be assumed to be under the same license as PolyVox.

/* coherent noise function over 1, 2 or 3 dimensions */
/* (copyright Ken Perlin) */

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

#include "Perlin.h"

#define B SAMPLE_SIZE
#define BM (SAMPLE_SIZE-1)

#define N 0x1000
#define NP 12   /* 2^N */
#define NM 0xfff

#define s_curve(t) ( t * t * (3.0f - 2.0f * t) )
#define lerp(t, a, b) ( a + t * (b - a) )

#define setup(i,b0,b1,r0,r1)\
	t = vec[i] + N;\
	b0 = ((int)t) & BM;\
	b1 = (b0+1) & BM;\
	r0 = t - (int)t;\
	r1 = r0 - 1.0f;

float Perlin::noise1(float arg)
{
	int bx0, bx1;
	float rx0, rx1, sx, t, u, v, vec[1];

	vec[0] = arg;

	if (mStart)
	{
		srand(mSeed);
		mStart = false;
		init();
	}

	setup(0, bx0, bx1, rx0, rx1);

	sx = s_curve(rx0);

	u = rx0 * g1[p[bx0]];
	v = rx1 * g1[p[bx1]];

	return lerp(sx, u, v);
}

float Perlin::noise2(float vec[2])
{
	int bx0, bx1, by0, by1, b00, b10, b01, b11;
	float rx0, rx1, ry0, ry1, *q, sx, sy, a, b, t, u, v;
	int i, j;

	if (mStart)
	{
		srand(mSeed);
		mStart = false;
		init();
	}

	setup(0, bx0, bx1, rx0, rx1);
	setup(1, by0, by1, ry0, ry1);

	i = p[bx0];
	j = p[bx1];

	b00 = p[i + by0];
	b10 = p[j + by0];
	b01 = p[i + by1];
	b11 = p[j + by1];

	sx = s_curve(rx0);
	sy = s_curve(ry0);

#define at2(rx,ry) ( rx * q[0] + ry * q[1] )

	q = g2[b00];
	u = at2(rx0, ry0);
	q = g2[b10];
	v = at2(rx1, ry0);
	a = lerp(sx, u, v);

	q = g2[b01];
	u = at2(rx0, ry1);
	q = g2[b11];
	v = at2(rx1, ry1);
	b = lerp(sx, u, v);

	return lerp(sy, a, b);
}

float Perlin::noise3(float vec[3])
{
	int bx0, bx1, by0, by1, bz0, bz1, b00, b10, b01, b11;
	float rx0, rx1, ry0, ry1, rz0, rz1, *q, sy, sz, a, b, c, d, t, u, v;
	int i, j;

	if (mStart)
	{
		srand(mSeed);
		mStart = false;
		init();
	}

	setup(0, bx0, bx1, rx0, rx1);
	setup(1, by0, by1, ry0, ry1);
	setup(2, bz0, bz1, rz0, rz1);

	i = p[bx0];
	j = p[bx1];

	b00 = p[i + by0];
	b10 = p[j + by0];
	b01 = p[i + by1];
	b11 = p[j + by1];

	t = s_curve(rx0);
	sy = s_curve(ry0);
	sz = s_curve(rz0);

#define at3(rx,ry,rz) ( rx * q[0] + ry * q[1] + rz * q[2] )

	q = g3[b00 + bz0]; u = at3(rx0, ry0, rz0);
	q = g3[b10 + bz0]; v = at3(rx1, ry0, rz0);
	a = lerp(t, u, v);

	q = g3[b01 + bz0]; u = at3(rx0, ry1, rz0);
	q = g3[b11 + bz0]; v = at3(rx1, ry1, rz0);
	b = lerp(t, u, v);

	c = lerp(sy, a, b);

	q = g3[b00 + bz1]; u = at3(rx0, ry0, rz1);
	q = g3[b10 + bz1]; v = at3(rx1, ry0, rz1);
	a = lerp(t, u, v);

	q = g3[b01 + bz1]; u = at3(rx0, ry1, rz1);
	q = g3[b11 + bz1]; v = at3(rx1, ry1, rz1);
	b = lerp(t, u, v);

	d = lerp(sy, a, b);

	return lerp(sz, c, d);
}

void Perlin::normalize2(float v[2])
{
	float s;

	s = (float)sqrt(v[0] * v[0] + v[1] * v[1]);
	s = 1.0f / s;
	v[0] = v[0] * s;
	v[1] = v[1] * s;
}

void Perlin::normalize3(float v[3])
{
	float s;

	s = (float)sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);
	s = 1.0f / s;

	v[0] = v[0] * s;
	v[1] = v[1] * s;
	v[2] = v[2] * s;
}

void Perlin::init(void)
{
	int i, j, k;

	for (i = 0; i < B; i++)
	{
		p[i] = i;
		g1[i] = (float)((rand() % (B + B)) - B) / B;
		for (j = 0; j < 2; j++)
			g2[i][j] = (float)((rand() % (B + B)) - B) / B;
		normalize2(g2[i]);
		for (j = 0; j < 3; j++)
			g3[i][j] = (float)((rand() % (B + B)) - B) / B;
		normalize3(g3[i]);
	}

	while (--i)
	{
		k = p[i];
		p[i] = p[j = rand() % B];
		p[j] = k;
	}

	for (i = 0; i < B + 2; i++)
	{
		p[B + i] = p[i];
		g1[B + i] = g1[i];
		for (j = 0; j < 2; j++)
			g2[B + i][j] = g2[i][j];
		for (j = 0; j < 3; j++)
			g3[B + i][j] = g3[i][j];
	}

}


float Perlin::perlin_noise_2D(float vec[2])
{
	int terms = mOctaves;
	float result = 0.0f;
	float amp = mAmplitude;

	vec[0] *= mFrequency;
	vec[1] *= mFrequency;

	for (int i = 0; i < terms; i++)
	{
		result += noise2(vec)*amp;
		vec[0] *= 2.0f;
		vec[1] *= 2.0f;
		amp *= 0.5f;
	}


	return result;
}

float Perlin::perlin_noise_3D(float vec[3])
{
	int terms = mOctaves;
	float result = 0.0f;
	float amp = mAmplitude;

	vec[0] *= mFrequency;
	vec[1] *= mFrequency;
	vec[2] *= mFrequency;

	for (int i = 0; i < terms; i++)
	{
		result += noise3(vec)*amp;
		vec[0] *= 2.0f;
		vec[1] *= 2.0f;
		vec[2] *= 2.0f;
		amp *= 0.5f;
	}


	return result;
}



Perlin::Perlin(int octaves, float freq, float amp, int seed)
{
	mOctaves = octaves;
	mFrequency = freq;
	mAmplitude = amp;
	mSeed = seed;
	mStart = true;
}

