/** 
 * @file llperlin.cpp
 *
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 * Copyright (c) 2001-2007, Linden Research, Inc.
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#include "linden_common.h"
#include "llmath.h"

#include "llperlin.h"

#define B 0x100
#define BM 0xff
#define N 0x1000
#define NF32 (4096.f)
#define NP 12   /* 2^N */
#define NM 0xfff

static S32 p[B + B + 2];
static F32 g3[B + B + 2][3];
static F32 g2[B + B + 2][2];
static F32 g1[B + B + 2];

bool LLPerlinNoise::sInitialized = 0;

static void normalize2(F32 v[2])
{
	F32 s = 1.f/(F32)sqrt(v[0] * v[0] + v[1] * v[1]);
	v[0] = v[0] * s;
	v[1] = v[1] * s;
}

static void normalize3(F32 v[3])
{
	F32 s = 1.f/(F32)sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);
	v[0] = v[0] * s;
	v[1] = v[1] * s;
	v[2] = v[2] * s;
}

static void fast_setup(F32 vec, U8 &b0, U8 &b1, F32 &r0, F32 &r1)
{
	S32 t_S32;

	r1	= vec + NF32;
	t_S32 = lltrunc(r1);
	b0 = (U8)t_S32;
	b1 = b0 + 1;
	r0 = r1 - t_S32;
	r1 = r0 - 1.f;
}


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

	for (i = 0 ; i < B ; i++)
	{
		p[i] = i;

		g1[i] = (F32)((rand() % (B + B)) - B) / B;

		for (j = 0 ; j < 2 ; j++)
			g2[i][j] = (F32)((rand() % (B + B)) - B) / B;
		normalize2(g2[i]);

		for (j = 0 ; j < 3 ; j++)
			g3[i][j] = (F32)((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];
	}

	sInitialized = true;
}


//============================================================================
// Noise functions

#define s_curve(t) ( t * t * (3.f - 2.f * t) )

#define lerp_m(t, a, b) ( a + t * (b - a) )

F32 LLPerlinNoise::noise1(F32 x)
{
	int bx0, bx1;
	F32 rx0, rx1, sx, t, u, v;

	if (!sInitialized)
		init();

	t = x + N;
	bx0 = (lltrunc(t)) & BM;
	bx1 = (bx0+1) & BM;
	rx0 = t - lltrunc(t);
	rx1 = rx0 - 1.f;

	sx = s_curve(rx0);

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

	return lerp_m(sx, u, v);
}

static F32 fast_at2(F32 rx, F32 ry, F32 *q)
{
	return rx * q[0] + ry * q[1];
}

F32 LLPerlinNoise::noise2(F32 x, F32 y)
{
	U8 bx0, bx1, by0, by1;
	U32 b00, b10, b01, b11;
	F32 rx0, rx1, ry0, ry1, *q, sx, sy, a, b, u, v;
	S32 i, j;

	if (!sInitialized)
		init();

	fast_setup(x, bx0, bx1, rx0, rx1);
	fast_setup(y, 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);


	q = *(g2 + b00);
	u = fast_at2(rx0, ry0, q);
	q = *(g2 + b10); 
	v = fast_at2(rx1, ry0, q);
	a = lerp_m(sx, u, v);

	q = *(g2 + b01); 
	u = fast_at2(rx0,ry1,q);
	q = *(g2 + b11); 
	v = fast_at2(rx1,ry1,q);
	b = lerp_m(sx, u, v);

	return lerp_m(sy, a, b);
}

static F32 fast_at3(F32 rx, F32 ry, F32 rz, F32 *q)
{
	return rx * q[0] + ry * q[1] + rz * q[2];
}

F32 LLPerlinNoise::noise3(F32 x, F32 y, F32 z)
{
	U8 bx0, bx1, by0, by1, bz0, bz1;
	S32 b00, b10, b01, b11;
	F32 rx0, rx1, ry0, ry1, rz0, rz1, *q, sy, sz, a, b, c, d, t, u, v;
	S32 i, j;

	if (!sInitialized)
		init();

	fast_setup(x, bx0,bx1, rx0,rx1);
	fast_setup(y, by0,by1, ry0,ry1);
	fast_setup(z, 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);

	q = g3[ b00 + bz0 ]; 
	u = fast_at3(rx0,ry0,rz0,q);
	q = g3[ b10 + bz0 ];
	v = fast_at3(rx1,ry0,rz0,q);
	a = lerp_m(t, u, v);

	q = g3[ b01 + bz0 ];
	u = fast_at3(rx0,ry1,rz0,q);
	q = g3[ b11 + bz0 ];
	v = fast_at3(rx1,ry1,rz0,q);
	b = lerp_m(t, u, v);

	c = lerp_m(sy, a, b);

	q = g3[ b00 + bz1 ];
	u = fast_at3(rx0,ry0,rz1,q);
	q = g3[ b10 + bz1 ];
	v = fast_at3(rx1,ry0,rz1,q);
	a = lerp_m(t, u, v);

	q = g3[ b01 + bz1 ];
	u = fast_at3(rx0,ry1,rz1,q);
	q = g3[ b11 + bz1 ];
	v = fast_at3(rx1,ry1,rz1,q);
	b = lerp_m(t, u, v);

	d = lerp_m(sy, a, b);

	return lerp_m(sz, c, d);
}

F32 LLPerlinNoise::turbulence2(F32 x, F32 y, F32 freq)
{
	F32 t, lx, ly;

	for (t = 0.f ; freq >= 1.f ; freq *= 0.5f)
	{
		lx = freq * x;
		ly = freq * y;
		t += noise2(lx, ly)/freq;
	}
	return t;
}

F32 LLPerlinNoise::turbulence3(F32 x, F32 y, F32 z, F32 freq)
{
	F32 t, lx, ly, lz;

	for (t = 0.f ; freq >= 1.f ; freq *= 0.5f)
	{
		lx = freq * x;
		ly = freq * y;
		lz = freq * z;
		t += noise3(lx,ly,lz)/freq;
//		t += fabs(noise3(lx,ly,lz)) / freq;					// Like snow - bubbly at low frequencies
//		t += sqrt(fabs(noise3(lx,ly,lz))) / freq;			// Better at low freq
//		t += (noise3(lx,ly,lz)*noise3(lx,ly,lz)) / freq;		
	}
	return t;
}

F32 LLPerlinNoise::clouds3(F32 x, F32 y, F32 z, F32 freq)
{
	F32 t, lx, ly, lz;

	for (t = 0.f ; freq >= 1.f ; freq *= 0.5f)
	{
		lx = freq * x;
		ly = freq * y;
		lz = freq * z;
//		t += noise3(lx,ly,lz)/freq;
//		t += fabs(noise3(lx,ly,lz)) / freq;					// Like snow - bubbly at low frequencies
//		t += sqrt(fabs(noise3(lx,ly,lz))) / freq;			// Better at low freq
		t += (noise3(lx,ly,lz)*noise3(lx,ly,lz)) / freq;		
	}
	return t;
}