/**
 * @file noise.cpp
 * @brief Perlin noise routines for procedural textures, etc
 *
 * $LicenseInfo:firstyear=2000&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "llviewerprecompiledheaders.h"

#include "noise.h"

#include "llrand.h"


// static
#define B 0x100
S32 p[B + B + 2];
F32 g3[B + B + 2][3];
F32 g2[B + B + 2][2];
F32 g1[B + B + 2];
S32 gNoiseStart = 1;


F32 noise2(F32 *vec)
{
    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 (gNoiseStart) {
        gNoiseStart = 0;
        init();
    }


    fast_setup(*vec, bx0, bx1, rx0, rx1);
    fast_setup(*(vec + 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);


    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);
}