#####################################################################
Charles,
Thanks for posting your problem .par/.frm's 'in public' on [Fractint]'s
email list serve:0
At some magnifications the apparent high count areas
disappear and at other magnifications they are massively
messed up.
And Jonathan,
Thanks for posting your response publicly on [Fractint]:
These PARs need to have periodicity adjusted. Using either
0 or 10 will work. If that doesn't fix the problem you are
seeing, let me know.
I have always wanted to see an example of a fractal that was sensitive
to whether periodicity= was specified and what values of periodicity
were useful.
Charles,
I tried all your fractals with both no periodicity= and periodicity=0
and 10 to see what the effects were of changing this parameter as
Jonathan suggested.
It would seem that the default periodicity (I think I remember that
it is around 3) works to speed up many fractals, but does not work
for a few -- like yours.
When I created your fractal InandOut with periodicity=0, I observed
that there were black ovals in it. I have previously learned that
these can sometimes be areas where the iteration limit (511 in your
fractal) has been exceeded. When I increased the iteration limit
(3rd line on the 'X' parameter page) to 5110 the black ovals filled in,
confirming my conjecture that these were 'under-iterated' areas.
I was not able to detect a slowdown in the speed that the fractal was
created, because so few pixels had iterations higher than 511.
Besides, raising the iteration limit fills in more pixels with colors
other than black and so gives what seems to me to be a more 'complete'
fractal.
Your particular color map (most easily seen by typing <E> and then
<Enter> while viewing your fractal) has so much yellow that I
thought that it might not allow some detail in the oval areas
to be seen, now that the pixels in this area were actually being
calculated.
To see if there was structure in the ovals I loaded a different
color map, TOPO.MAP (<L> while in the <E> color 'Palette Editing'
utility). Sure enough, there were the multiple copies of the 512
entry TOPO color map repeated in the spiral now in the oval areas
as the spiral 'wound' inward. This repeating of the color map
shows that more than 512 iterations took place in the oval areas.
Section 8.2.1 "Periodicity Logic" in the Fractint 20.0
Documentation gives a pretty good explanation of what Fractint's
periodicity feature is and the speedup it can do for you.
In that discussion "in the lake" refers to the "inside" color
of zero iterations, often colored black or blue.
But you have happened by chance to be calculating a fractal that
is sensitive to the default value of periodicity in Fractint and
needs to have this parameter adjusted. As Jonathan suggested,
periodicity=0 or =10 seem to work well for your fractal.
In Damien M. Jones Windows tips in the Fractint 20.0 Docs I also
note his:
"Holes" in an image while it is being drawn:
Little squares colored in your "inside" color, in a pattern of every
second square of that size, in solid guessing mode, both across and
down (i.e., 1 out of 4), are a symptom of an image which should be
calculated with more conservative periodicity checking than the
default. See the Periodicity parameter under Image Calculation
Parameters (p. 116).
I'm sorry if I am belaboring common knowledge, but for me when I
learned the practical aspects of underiterated fractals, and the
sensitivity of fractals to color maps, they were powerful
revelations that allowed me to improve my fractals greatly.
Jonathan,
Thanks for helping me understand the correct use of the
periodicity= parameter.
- Hal Lane
#########################
# hallane(a)earthlink.net #
#########################
#####################################################################
>
>Message: 5
>Date: Thu, 08 Mar 2007 21:56:42 -0500
>From: Charles F Crocker <chasc(a)pop.gis.net>
>Subject: [Fractint] GIF File format
>To: Fractint and General Fractals Discussion
> <fractint(a)mailman.xmission.com>
>Message-ID: <4.2.2.20070308214642.02d1c6c0(a)pop.gis.net>
>Content-Type: text/plain; charset="us-ascii"; format=flowed
>
>Where in a Fract???.gif file does the Fractint data appear? I have a
>question and want to be on sound ground before I raise it. All I can
>identify is that the file starts with GIF98a and near the end there is a
>little plain text that is "fractint001 Fractal" with the space actually
>being y with an umlaut over it. Nothing else identifiable as plain text.
>The point I particularly want to know about is how the V screen parameters
>are included.
>
>My Fractint computer had a disastrous breakdown a couple of months ago and
>am trying to recover and also evaluate ver 99. I ran across a floppy disk
>that was labeled "Problems" and am passing along one of them.
>
>Here is my Newpar.par file which includes the formula. The original
>parameter file was run on Fractint 99 and then recorded again. It doesn't
>show as much of the problem that showed originally but as you zoom in
>amazing things happen. At some magnifications the apparent high
>count areas
>disappear and at other magnifications they are massively messed up.
>
>Start parameter file.
>
>Julia { ; Parameter file recorded on Win 98 system in DOS mode
> ; Version 2002 Patchlevel 3
> ; Only a trace of original problem
> ; Fractint Version 2099 Patchlevel 8
> ; Fractint Version 2099 Patchlevel 8
> reset=2099 type=julia4 passes=1
> center-mag=6.199e-006/-2.265e-006/2.109716
> params=-1.0296017527580259/0.19608962535858149 float=y maxiter=4097
>
>colors=00000000z<3>PPzVVz``z<3>zzzzzzzzzz00z00<4>zS0zY0zc0<3>zz0<227>zz0 }
>
>Problem { ; Zoom on high count area.
> ; Version 2002 Patchlevel 3
> ; Fractint Version 2099 Patchlevel 8
> ; Fractint Version 2099 Patchlevel 8
> reset=2099 type=julia4 passes=1 center-mag=0.42653/0.312698/17.29275
> params=-1.0296017527580259/0.19608962535858149 float=y maxiter=4097
>
>colors=00000000z<3>PPzVVz``z<3>zzzzzzzzzz00z00<4>zS0zY0zc0<3>zz0<227>zz0 }
>
>InandOut { ; After various zooms.
> ; Version 2002 Patchlevel 3
> ; Fractint Version 2099 Patchlevel 8
> ; Fractint Version 2099 Patchlevel 8
> reset=2099 type=julia4 center-mag=0.427258/0.296879/9.281967/1.0001
> params=-1.0296017527580259/0.19608962535858149 float=y maxiter=511
>
>colors=00000000z<3>PPzVVz``z<3>zzzzzzzzzz00z00<4>zS0zY0zc0<3>zz0<227>zz0 }
>
>frm:julia4 {; Chuck Ebbert added 13 Jan 1993
> ; p1=Parameter (default (.6,.55) )
> ; bailout is real(p2) (default 4)
> ; force c=(.6,.55) if p1=0
> z = pixel, c = ((0.6,0.55) * (|p1|<=0) + p1 )
> t = (4 * (real(p2)<=0) + real(p2) * (0<p2) ):
> z = sqr(z*z) + c
> |z| <= t }
>
>End parameter file.
>
>Charles
>
>------------------------------
>
>Message: 6
>Date: Thu, 08 Mar 2007 21:34:24 -0600
>From: Jonathan Osuch <osuchj(a)avalon.net>
>Subject: Re: [Fractint] GIF File format
>To: Fractint and General Fractals Discussion
> <fractint(a)mailman.xmission.com>
>Message-ID: <1173411264.3906.10.camel(a)linux.site>
>Content-Type: text/plain
>
>Charles,
>
>> Where in a Fract???.gif file does the Fractint data appear? I have a
>> question and want to be on sound ground before I raise it. All I can
>> identify is that the file starts with GIF98a and near the end there is a
>> little plain text that is "fractint001 Fractal" with the space actually
>> being y with an umlaut over it. Nothing else identifiable as plain text.
>> The point I particularly want to know about is how the V screen
>parameters
>> are included.
>
>It should be shortly after the GIF89a, as part of the standard GIF file
>format. You would need to look at the GIF specification. I don't
>believe we save any data from the <v> screen in the Fractint specific
>data segments. There is a very old DOS program called F-DATA by Marc
>Reinig, that can extract Fractint specific data from GIFs. It is not
>up-to-date so it won't see new parameters, but it is real good with the
>basics. I suspect if you would like to use it I'll have to email it to
>you, since a Google search didn't find it.
>
>> My Fractint computer had a disastrous breakdown a couple of
>months ago and
>> am trying to recover and also evaluate ver 99. I ran across a
>floppy disk
>> that was labeled "Problems" and am passing along one of them.
>>
>> Here is my Newpar.par file which includes the formula. The original
>> parameter file was run on Fractint 99 and then recorded again.
>It doesn't
>> show as much of the problem that showed originally but as you zoom in
>> amazing things happen. At some magnifications the apparent high
>count areas
>> disappear and at other magnifications they are massively messed up.
>
>***************************************************************************
********
>
>These PARs need to have periodicity adjusted. Using either 0 or 10 will
>work. If that doesn't fix the problem you are seeing, let me know.
>
>Jonathan
>
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.413 / Virus Database: 268.18.9/719 - Release Date: 3/12/07
