Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!ucbvax!EN.ECN.PURDUE.EDU!eldorado
From: eldorado@EN.ECN.PURDUE.EDU (David D Jansen)
Newsgroups: comp.sys.apple
Subject: AE, Mandelbrot generator
Message-ID: <9002071850.AA29665@en.ecn.purdue.edu>
Date: 7 Feb 90 18:50:34 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 66

Keywords: mandelbrot

Could someone with fractal experience tell me why I get weird data.  It gets
the basic shape but not quite right.  A friend of mine (a fractal "guru")
can't make out what the problem.  Here is my type declaration:

type 
imaginary = record {an imaginary number  i.e. a + bi}
              a : real;
              b : real;
            end;
region = record {a rectangle on the imaginary plane}
           amin : real;
           bmin : real;
           amax : real;
           bmax : real;
	 end;
screen = record {the data that describes a screen}
           where : region;
           bitmap : packed array [1..hor,1..ver] of boolean;
 	end;

procedure plotset (var pages:screen;var fraccalc:boolean);
{a procedure to put the fractal from the sent region into the variable page}
var
dval,z,val:imaginary;
h,v,n:integer;
begin
  dval.a:=(pages.where.amax - pages.where.amin)/(hor - 1); 
  dval.b:=(pages.where.bmax - pages.where.bmin)/(ver - 1); 
  for v:=1 to ver do
  begin
    for h:=1 to hor do
    begin
      val.a:=pages.where.amin + (h - 1) * dval.a; {val is the value of the}
      val.b:=pages.where.bmin + (v - 1) * dval.b; {current point on the screen}
      n:=0;
      z.a:=0;
      z.b:=0;
      while ((z.a*z.a) + (z.b*z.b) <= 4) and (n < maxiter) do
      begin
        z.a:=(z.a * z.a) - (z.b * z.b) + val.a;
        z.b:=2 * z.a * z.b + val.b;
        n:=n + 1;
      end;
      if (((z.a * z.a) + (z.b * z.b)) <= 4) then
        pages.bitmap[h,v]:=true
    end;
    writeln (v/ver*100:5:2,'% done');
  end;
  fraccalc:=true;
end;

Someone last year uploaded a mandelbrot generator and I modified his code to
test in my program.  No go, it was worse than my attempt.  I don't think I
tested my code in his program.  That was a mistake on my part.  I have had 
this problem for more than a year.  There could be a reward for the correct
answer.
While I am at it, what is Applied Engineering's phone number?  Did anyone
download the Prodos Hyper C that was uploaded?  Did it work?


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

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