/**
 * @(#) $RCSfile: SmoothNoiseLoop.as,v $ $Revision: 1.1 $ $Date: 2003/04/20 13:13:18 $
 *
 * Copyright 2003 Orgdot AS. All Rights Reserved.
 * http://dev.swfit.com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 
 330, Boston, MA  02111-1307, USA.
 */

/**
 * Loop script for simple smooth noise generator. Quadratic interpolation in two dimensions.
 *
 * @author      Olaf Havnes
 * @version     $Revision: 1.1 $ $Date: 2003/04/20 13:13:18 $
 * @since       SWFIT1.0
 */

// Generate some noise to start with. We need to seed the methods below,
// so that the curve does not start out flat.
if (y0 eq "")
{
    // Store for other clips.
    _level0.NOISE_RAND_SPACE = RAND_SPACE;
    _level0.NOISE_NUM_POINTS = ARR_LEN;

    sum_y = 0;
    i = 0;
    while (i < ARR_LEN)
    {
        y = random (RAND_SPACE);
        set ("y" add i, y);

        // Sum needed to calculate smooth derivates along the new curve
        sum_y = y - sum_y;

        i++;
    }

    // Coeffecients for the last point in the curve. Treat separately, since the curve loops back.
    c = y;
    b = 2 * (sum_y - y);
    a = y0 - b - c;

    // Store
    i--;
    set ("_c" add i, c);
    set ("_b" add i, b);
    set ("_a" add i, a);

    // Start from the beginning again.
    i = 0;
    while (i < ARR_LEN - 1)
    {
        c_ = c;
        c = eval ("y" add i);
        b = 2 * (c - c_) - b;
        a = eval ("y" add (i+1)) - b - c;

        // Store
        set ("_c" add i, c);
        set ("_b" add i, b);
        set ("_a" add i, a);



        i++;
    }

    // Make sure we do the next block of code on this first run.
    loop_life_counter = LOOP_LIFE;
}


// This here big block should be run very seldom ...
loop_life_counter++;
if (loop_life_counter >= LOOP_LIFE)
{
    loop_life_counter = 0;

    sum_y = 0;
    i = 0;
    while (i < ARR_LEN)
    {
        y = random (RAND_SPACE);
        set ("y" add i, y);

        // Sum needed to calculate smooth derivates along the new curve
        sum_y = y - sum_y;
        i++;
    }

    // Coeffecients for the last point in the curve. Treat separately, since the curve loops back.
    c = y;
    b = 2 * (sum_y - y);
    a = y0 - b - c;

    // Shift the old values and store the new ones
    i--;
    set ("c" add i, eval ("_c" add i));
    set ("b" add i, eval ("_b" add i));
    set ("a" add i, eval ("_a" add i));

    set ("_c" add i, c);
    set ("_b" add i, b);
    set ("_a" add i, a);

    // Start from the beginning again.
    i = 0;
    while (i < ARR_LEN - 1)
    {
        c_ = c;
        c = eval ("y" add i);
        b = 2 * (c - c_) - b;
        a = eval ("y" add (i+1)) - b - c;

        // Shift the old values and store the new ones
        set ("c" add i, eval ("_c" add i));
        set ("b" add i, eval ("_b" add i));
        set ("a" add i, eval ("_a" add i));

        set ("_c" add i, c);
        set ("_b" add i, b);
        set ("_a" add i, a);

        i++;
    }

    // Aye, and here comes the rub indeed - we need to interpolate across these 
    // coeffecients to change the curve smoothly over time. Which means we need
    // coeffecients for the coeffecients ... And this we do with cubic interpolation.

    i = 0;
    while (i < ARR_LEN)
    {
        // First we do the 'a coeffecient'.
        start_slope = eval ("slope_a" add i);
        coef_0 = eval ("a" add i);
        coef_1 = eval ("_a" add i);
        end_slope = coef_1 - coef_0;

        // Compute and store the coeffecients for the 'a coeffecient'.
        set ("ad" add i, coef_0);
        set ("ac" add i, start_slope);
        set ("ab" add i, 3 * coef_1 - 3 * coef_0 - end_slope - 2 * start_slope);
        set ("aa" add i, end_slope + start_slope - 2 * coef_1 + 2 * coef_0);

        // Store the end slope value for the 'a coeffecient'.
        set ("slope_a" add i, end_slope);


        // Repeat for the 'b coeffecient'.
        start_slope = eval ("slope_b" add i);
        coef_0 = eval ("b" add i);
        coef_1 = eval ("_b" add i);
        end_slope = coef_1 - coef_0;

        // Compute and store the coeffecients for the 'b coeffecient'.
        set ("bd" add i, coef_0);
        set ("bc" add i, start_slope);
        set ("bb" add i, 3 * coef_1 - 3 * coef_0 - end_slope - 2 * start_slope);
        set ("ba" add i, end_slope + start_slope - 2 * coef_1 + 2 * coef_0);

        // Store the end slope value for the 'b coeffecient'.
        set ("slope_b" add i, end_slope);


        // Repeat for the 'c coeffecient'.
        start_slope = eval ("slope_c" add i);
        coef_0 = eval ("c" add i);
        coef_1 = eval ("_c" add i);
        end_slope = coef_1 - coef_0;

        // Compute and store the coeffecients for the 'c coeffecient'.
        set ("cd" add i, coef_0);
        set ("cc" add i, start_slope);
        set ("cb" add i, 3 * coef_1 - 3 * coef_0 - end_slope - 2 * start_slope);
        set ("ca" add i, end_slope + start_slope - 2 * coef_1 + 2 * coef_0);

        // Store the end slope value for the 'c coeffecient'.
        set ("slope_c" add i, end_slope);



        i++;
    }
}


// Store a full set of coeffecients in _level0. This method is run every frame.

cx = loop_life_counter / LOOP_LIFE;
cx2 = cx * cx;
cx3 = cx2 * cx;

i = 0;
while (i < ARR_LEN)
{
    set 
    (
        "/:loop_noise_a_" add i, 
        eval ("aa" add i) * cx3 + eval ("ab" add i) * cx2 + eval ("ac" add i) * cx + eval ("ad" add i)
    );
    set 
    (
        "/:loop_noise_b_" add i, 
        eval ("ba" add i) * cx3 + eval ("bb" add i) * cx2 + eval ("bc" add i) * cx + eval ("bd" add i)
    );
    set 
    (
        "/:loop_noise_c_" add i, 
        eval ("ca" add i) * cx3 + eval ("cb" add i) * cx2 + eval ("cc" add i) * cx + eval ("cd" add i)
    );
    i++;
}