[comp.sys.apple] Mandelbrots, Julia Sets

eldorado@EN.ECN.PURDUE.EDU (David D Jansen) (02/11/90)

Keywords: Julia Set


To all those who helped solve the Mandelbrot generator, THANK YOU!!  Here
is another challenge for you, if ya feel up ta it.  I don't know much about
fractals.  What I do know about the Julia set is, you take a point, square
it, add a constant and repeat the procedure.  But what exactly happens
if it goes to 1 (or in this case two squared) after a given number of
iterations, I am not sure.  I believe that is where my problem is.  I
thought that the point is in the set if it goes to 1 after say 100 iterations.
Again, I would appreciate any help I can get.  It has the same type declaration
as the previous posting.  I may write a fractal mountain procedure if YOU
feel up to it :^).

procedure generatingxy (var pages:screen;c:imaginary;var fraccalc:boolean);
var
hold:real;
complex:imaginary;
numittr:integer;
length:real;
xloop:integer;
yloop:integer;
begin
  for xloop:=1 to hor do
  begin
 complex.a:=(xloop/hor*(pages.where.max.a-pages.where.min.a))+pages.where.min.a;
    for yloop:=1 to ver do
    begin
 complex.b:=(yloop/ver*(pages.where.max.b-pages.where.min.b))+pages.where.min.b;
      numittr:=0;
      repeat
        hold:=complex.a;
        length:=sqr(complex.a) + sqr(complex.b);
        complex.a:=length + c.a;
        complex.b:=2 * hold * complex.b + c.b;
        numittr:=numittr + 1;
      until (length < squaredradius) or (numittr = maxiter);
      if (length <= squaredradius) and (numittr = maxiter) then
	pages.bitmap[xloop,yloop]:=true;
    end;
    writeln (xloop/hor*100:5:2,'% done');
  end;
  fraccalc:=true;
end;


Dave Jansen (The Gilded One)
eldorado@en.ecn.purdue.edu

"We have to make all our programs idiot-proof.  Idiots are very intelligent!"