Complex curved line

program new;

var
  BMP: TImage;

type
  Vector2 = record x,y: Single; end;

function Vector2.ToPoint(): TPoint;
begin
  Result := [Round(Self.x), Round(Self.y)];
end;

function GenSubPoints(A,B:Vector2; count: Int32): array of Vector2;
var
  t,d,r,rx,ry,step: Double;
  i,j,k: Int32;
  vec: Vector2;
  v,tmp: array of Vector2;
begin
  if count = 0 then Exit([A,B]);
  d := Hypot(A.x-B.x, B.y-B.y) / count;
  SetLength(v, count);
  v[0] := A;

  r := d*RandomMean(-0.75,0.75);
  for i:=1 to count-1 do
  begin
    t := RandomMode(0.5,-1.0,1.5);
    v[i].x := (1 - t) * v[i - 1].x + t * B.x + r;
    v[i].y := (1 - t) * v[i - 1].y + t * B.y + r;
  end;
  v[count-1] := B;

  step := Max(0.01, 1/Sqr(count));
  t := 0;
  while t <= 1 do
  begin
    tmp := Copy(v);
    for i:=High(tmp) downto 1 do
      for k:=0 to i-1 do
      begin
        tmp[k].x := tmp[k].x + (tmp[k+1].x - tmp[k].x) * t;
        tmp[k].y := tmp[k].y + (tmp[k+1].y - tmp[k].y) * t;
      end;
    vec := tmp[0];
    Result += vec;
    t += step;
  end;
  Result += B;
end;


function SmoothLine(src, dst: Vector2; Gravity, NoiseLevel, maxStep: Double; Sharpness:Int32; targetArea:Double): TPointArray;
var
  t,noiseX,noiseY,dist,xstep,ystep,len,newDist,rmaxStep,rNoise,rGravity: Single;
  i: Int32;
  prev,tmp: TPoint;
  line: TPointArray;
  v: array of Vector2;
const
  PI2 := PI/2;
begin
  v := GenSubPoints(src,dst, sharpness);
  //for i:=0 to High(v) do
  //  BMP.DrawCircle(v[i].ToPoint, 3);

  noiseX := Random();
  noiseY := Random();

  Result += src.ToPoint;
  prev := src.ToPoint;

  rMaxStep := maxStep;
  rNoise   := NoiseLevel;
  rGravity := Gravity;

  i := 1;
  dst := v[i];
  dist := Hypot(src.x - dst.x, src.y - dst.y);
  while (Hypot(src.x - v[High(v)].x, src.y - v[High(v)].y) > 1) do
  begin
    if (dist < targetArea) then
    begin
      if (i = High(v)) then
      begin
        if (rMaxStep > 1) then rMaxStep /= SQRT_2;
      end else
      begin
        dst := v[Inc(i)];
        rMaxStep := Max(SQRT_2, Min(MaxStep, Hypot(src.x - v[i].x, src.y - v[i].y)));

        if rMaxStep >= SQRT_5 then
        begin
          rNoise   := NoiseLevel;
          rGravity := Gravity;
        end else
        begin
          rNoise := 0;
          rGravity := 1;
        end;
      end;
    end;

    noiseX := noiseX * 2/3 + (2*Random()-1) * rNoise * 1/3;
    noiseY := noiseY * 2/3 + (2*Random()-1) * rNoise * 1/3;
    xstep := noiseX + rGravity * (dst.x-src.x) / dist;
    ystep := noiseY + rGravity * (dst.y-src.y) / dist;
    len := Hypot(xstep, ystep);

    if (len > rMaxStep) then
    begin
      newDist := 1+Random() * rMaxStep;
      xstep := (xstep / len) * newDist;
      ystep := (ystep / len) * newDist;
    end;

    src.x += xstep;
    src.y += ystep;
    tmp.x := Round(src.x);
    tmp.y := Round(src.y);

    if (tmp <> prev) then
    begin
      if len <= SQRT_2 then
        result += tmp
      else
      begin
        //line := TPointArray.CreateFromLine(prev, tmp);
        result += tmp;//line;
      end;
    end;

    dist := Hypot(src.x - dst.x, src.y - dst.y);
    prev := tmp;
  end;
end;


var
  p,q: TPoint;
  a: TPoint=[50,150];
  b: TPoint=[600,150];
  i,c: Int32;
begin
  bmp := TImage.Create(700,700);
  bmp.Show();

  while True do
  begin
    bmp.DrawColor := Random($FFFFFF);
    bmp.Clear();

    q := a;
    for p in SmoothLine([a.x,a.y], [b.x,b.y], 7, 2.5, 10, 7, 40) do
    try
      if InRange(p.x, 0,bmp.Width-1) and InRange(p.y, 0,bmp.Height-1) then
        bmp.DrawLineAA(q,p,2);

      q := p;
      Inc(i);


      DebugImageUpdate(bmp);
    except end;

    //a.y += 20;
    //b.y += 20;

    //DebugImageUpdate(bmp);
    //Sleep(500);
  end;
  bmp.Show(False);
end.