POV-Ray : Newsgroups : povray.general : Did I miss anything? (parent/child texture in CSG) Server Time
19 May 2024 22:58:10 EDT (-0400)
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From: William F Pokorny
Subject: Re: Did I miss anything? (parent/child texture in CSG)
Date: 14 Feb 2024 07:16:50
Message: <65ccaf32$1@news.povray.org>
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:


yesbird, a year ago in February of 2023 created and posted alternate web 


For browsing:


Source is here:

(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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From: Ilya Razmanov
Subject: Re: Did I miss anything? (parent/child texture in CSG)
Date: 19 Feb 2024 06:40:40
Message: <65d33e38$1@news.povray.org>
On 13.02.2024 4:14, William F Pokorny wrote:
> On 2/8/24 04:01, Ilya Razmanov wrote:
>> Any ideas regarding what may be the right place to get something to read?
> Glad Bill W got you started with answers.
> I'd add that a look at the documentation for isosurface and parametric 
> surfaces - which are based on functions - might help. There are user 

Thanks everybody, now I seem to have more than enough for my old brain 
to digest, so you are unlikely to be bothered by me for quite a while 
(unless, of course, I come up with more questions).

Ilya Razmanov

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