{$INCLUDE "options.inc"}

unit uLandGenPerlin;

interface

procedure GenPerlin;

implementation

uses uVariables, uConsts, uRandom, math; // for min()

var fadear: array[byte] of LongInt;

    p: array[0..511] of LongInt;

function fade(t: LongInt) : LongInt; inline;

var t0, t1: LongInt;

begin

    t0:= fadear[t shr 8];

    t1:= fadear[min(255, t shr 8 + 1)];

    fade:= t0 + ((t and 255) * (t1 - t0) shr 8)

end;

function lerp(t, a, b: LongInt) : LongInt; inline;

begin

    lerp:= a + (t * (b - a) shr 12)

end;

function grad(hash, x, y: LongInt) : LongInt;

var h, v, u: LongInt;

begin

    h:= hash and 15;

    if h < 8 then u:= x else u:= y;

    if h < 4 then v:= y else

        if (h = 12) or (h = 14) then v:= x else v:= 0;

    if (h and 1) <> 0 then u:= -u;

    if (h and 2) <> 0 then v:= -v;

    grad:= u + v

end;

function inoise(x, y: LongInt) : LongInt;

const N = $10000;

var xx, yy, u, v, A, AA, AB, B, BA, BB: LongInt;

begin

    xx:= (x shr 16) and 255;

    yy:= (y shr 16) and 255;

    x:= x and $FFFF;

    y:= y and $FFFF;

    u:= fade(x);

    v:= fade(y);

    A:= p[xx    ] + yy; AA:= p[A]; AB:= p[A + 1];

    B:= p[xx + 1] + yy; BA:= p[B]; BB:= p[B + 1];

    inoise:=

            lerp(v, lerp(u, grad(p[AA  ], x   , y  ),

                            grad(p[BA  ], x-N , y  )),

                    lerp(u, grad(p[AB  ], x   , y-N),

                            grad(p[BB  ], x-N , y-N)));

end;

function f(t: double): double;

begin

    f:= t * t * t * (t * (t * 6 - 15) + 10);

end;

procedure inoise_setup();

var i, ii, t: LongInt;

begin

    for i:= 0 to 254 do

        p[i]:= i + 1;

    p[255]:= 0;

    for i:= 0 to 254 do

    begin

        ii:= GetRandom(256 - i) + i;

        t:= p[i];

        p[i]:= p[ii];

        p[ii]:= t

    end;

    for i:= 0 to 255 do

        p[256 + i]:= p[i];

    for i:= 0 to 255 do

        fadear[i]:= trunc($1000 * f(i / 256));

end;

const detail = 120000*3;

    field = 3;

    width = 4096;

    height = 2048;

procedure GenPerlin;

begin

    inoise_setup();

    for y:= 1024 to pred(height) do

    begin

        di:= detail * field * y div height;

        for x:= 0 to pred(width) do

        begin

            dj:= detail * field * x div width;

            r:= (abs(inoise(di, dj))) shr 8 and $ff;

            //r:= r - max(0, - abs(x - width div 2) + width * 2 div 100); // split vertically in the middle

            //r:= r + (trunc(1000 - sqrt(sqr(x - (width div 2)) * 4 + sqr(y - height * 5 div 4) * 22))) div 600 * 20; // ellipse

            if r < 0 then Land[y, x]:= 0 else Land[y, x]:= lfBasic;

        end;

    end;

    leftX:= 0;

    rightX:= 4095;

    topY:= 0;

    hasBorder:= false;

end;

end.