

On 2/13/24 06:32, Bald Eagle wrote:
> I think the document (pdf) is ~4mb, and the zip is 176 kb.
> Perhaps we can find a spot to host the files? The Wiki?
> A link from the main page? References?
I have in my head someone already posted copies of the tutorial...
The fastest is probably to post a tarball to povray.binary.tutorials.
And, there they are!

Pekka Aho in May 2021:
https://news.povray.org/povray.binaries.tutorials/thread/%3Cweb.609fe84ffb749b2cbac92b0947dba873%40news.povray.org%3E/

yesbird, a year ago in February of 2023 created and posted alternate web
sites:
http://news.povray.org/povray.binaries.tutorials/thread/%3C63f215a6%241%40news.povray.org%3E/
For browsing:
https://povlab.online/isotutorial/
Archived:
https://povlab.online/arc/iso_tut.zip
Source is here:
http://web.archive.org/web/20190728000430/http://www.econym.demon.co.uk/isotut/index.htm

YB
(I'll make a note in my local  somewhat hacked up  version of the
examples from that tutorial so hopefully I see it next time I dive in
there for something.)
======
Aside: When I posted the modified version of cylcoords.pov as
cylcoords1.pov a thing that bothered me was the hard coded compensation
scaling for the twist distortion. I'd worked out a formula years ago,
but couldn't remember it (or find it) in the moment. Playing around some
I came up with '(1/Turns)*(1/R2)', which I think was it..? So instead of
*
f_helix1(x,z,y, Strands, +Turns, R1, R2, 1, 0.8, 20)
this is likely better:
****************
f_helix1(x,z,y, Strands, +Turns, R1, R2, (1/Turns)*(1/R2), 0.8, 20)
Note! The formula works less well with other than spherical / near
spherical base shapes. The base positions also start somewhat twisted
according to the thread, which doesn't matter for a spherical base
shape, but it does to some amount otherwise.
With that formula in place and using a pure sphere base (0.8 > 1.0),
some might find setting Turns to something like 1/1000 interesting. It's
possible to get quite a few interesting shapes  not helix like  out of
the f_helix1() function!
For fun, another image using the compensation formula.
Bill P.
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