POV-Ray : Newsgroups : povray.binaries.images : HELP REQUEST: Twisted Ropes of Ballista Server Time: 30 Mar 2020 14:31:18 GMT
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From: Sven Littkowski
Subject: HELP REQUEST: Twisted Ropes of Ballista
Date: 2 Mar 2020 02:50:02
Message: <web.5e5c73481f80037d16061d710@news.povray.org>
Please see the attached downloadable RAR archive file. It contains all necessary
files.

PROBLEM

I am developingm an authentic classical Roman ballista. Those are the
predecessors of the later guns. They use the energy that rope fibers can store.

The ballista is not finished yet, but I am not able to create those twisted
ropes, after one entire day of fruitless attempts. I cannot manage the spline
object, that's the problem.

The attached archive contains a folder called "Example", there you can find a
graphic that shows what is needed (the twisted brown ropes left and right).

If here's anyone who has the ability to help me out, it would be great! All
POV-Ray scene-related files are inside the other three folders.

As a small Thank You for your time, intention and efforts, the archive also
contains another folder by the name of "PCP" - this means "POV-Ray Color Picker"
(for Windows), and lets you select colors and converts them into POV-Ray code.
Very useful.

Please don't hes to ask me, if you have questions. Big thanks.


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Attachments:
Download 'ballista 001.rar.dat' (2487 KB)

From: Sven Littkowski
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 2 Mar 2020 04:30:00
Message: <web.5e5c8a9f5f4031dc16061d710@news.povray.org>
Here's the preview.


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From: Sven Littkowski
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 2 Mar 2020 16:40:01
Message: <web.5e5d35a95f4031dc594a84930@news.povray.org>
New attempt to show image...


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Attachments:
Download 'sl - roman ballista 001.jpg' (873 KB)

Preview of image 'sl - roman ballista 001.jpg'
sl - roman ballista 001.jpg


 

From: Bald Eagle
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 2 Mar 2020 18:20:01
Message: <web.5e5d4dca5f4031dc4eec112d0@news.povray.org>
"Sven Littkowski" <nomail@nomail> wrote:

> The ballista is not finished yet, but I am not able to create those twisted
> ropes, after one entire day of fruitless attempts. I cannot manage the spline
> object, that's the problem.

Does this help any?
http://news.povray.org/povray.binaries.images/thread/%3C3c4d365b%40news.povray.org%3E/

In object collection.

Or do you need a function to wrap the rope around the spindle?


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From: Sven Littkowski
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 2 Mar 2020 23:10:01
Message: <web.5e5d91615f4031dc2e40bb200@news.povray.org>
Hi BaldEagle,

nice hearing again from you, and thanks for yout time.

It is not quite a wraping around the cylinder that I need, it is several ropes
pushed sideways where the horizontal arm extends from the vertical cylinder.
This is something that I cannot do with my current level of POV-skills. I am,
actually, quite desperate and frustrated.   :-)

I believe it would be easier to use another render software with a WYSIWYG
editor, and simply visually push the individual ropes sideways, some more, some
less, some not. And then to export that object as mesh for POV-Ray. But I do not
have any other render software on this machine, and I am at the hospital
rightnow, data through mobile phone is expensive. Cannot downloaDo you know of
any way to achieve a solution for the rope problem? I imagine, the sphere-sweep
spline or other splines can be the solution, but I have no understanding of them
and always get bad results. I cannot control their directions die lack of
understanding.


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From: Bald Eagle
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 2 Mar 2020 23:55:00
Message: <web.5e5d9c255f4031dc4eec112d0@news.povray.org>
"Sven Littkowski" <nomail@nomail> wrote:

> It is not quite a wraping around the cylinder that I need, it is several ropes
> pushed sideways where the horizontal arm extends from the vertical cylinder.

Nice image  :)   But It looks like the part you need is hidden from view.
Maybe just sketch out a diagram and post a photo of what you need?
(It doesn't need to be parameterizable / animated, does it?)


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From: Sven Littkowski
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 3 Mar 2020 01:05:00
Message: <web.5e5dabfd5f4031dc2e40bb200@news.povray.org>
Hope this helps.

The vertical cylinder where the ropes go around has a diamter of 0.25 and a
height from < 0.0, 0.0, 0.0 > to < 0.0, 2.7, 0.0 >.

The arm separates from the middle of the cylinder#s height and has an own radius
of 0.2 there.

Excerpt:

 union // sling arm
 {
  cylinder { < 0.0, -0.2, 0.0 > < 0.0, 2.5, 0.0 > 0.25 texture { TopColor rotate
< 90.0, 0.0, 0.0 > } }
  cone { < 0.0,  1.15,  3.0 > 0.15 < 0.0, 1.15, 0.0 > 0.2 texture { TopColor } }
  box { < 0.0, 1.00,  3.0 > < 0.18, 1.30,  2.5 > texture { RustyIron } }
  cylinder { < 0.0, 1.15,  3.0 > < 0.0, 1.15,  2.9 > 0.17 texture { RustyIron }
}
  cylinder { < 0.0, 1.15,  2.7 > < 0.0, 1.15,  2.6 > 0.18 texture { RustyIron }
}
  torus { 0.15, 0.05 translate < 0.18, 1.15,  2.75 > texture { RustyIron } }
  sphere { < 0.0, 1.15,  3.0 > 0.15 texture { RustyIron } }
  torus { 0.05, 0.025 rotate < 90.0, 0.0, 0.0 > translate < 0.33, 1.15,  2.75 >
texture { Rope } } //  // ropes around rings
  cylinder { < 0.33, 1.15,  2.75 > < 4.19, 1.275,  3.7825 > 0.025 texture { Rope
} }
  rotate < 0.0, 55.0, 0.0 >
  translate < -1.5, 0.0,  1.32 >
 }
The first cylinder is the vertical one (rope skein), and the first cone is the
arm.

The ropes need to have a cross-section radius larger tan 0.025, maybe 0.030 or
0.035 maximum.


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From: Sven Littkowski
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 3 Mar 2020 01:10:00
Message: <web.5e5dad415f4031dc2e40bb200@news.povray.org>
Examples...


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Attachments:
Download 'details - 001.jpg' (229 KB)

Preview of image 'details - 001.jpg'
details - 001.jpg


 

From: Bald Eagle
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 3 Mar 2020 03:15:00
Message: <web.5e5dcb9b5f4031dc4eec112d0@news.povray.org>
So, basically you want something like this:


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Attachments:
Download 'romanballista.png' (67 KB)

Preview of image 'romanballista.png'
romanballista.png


 

From: Sven Littkowski
Subject: Re: HELP REQUEST: Twisted Ropes of Ballista
Date: 3 Mar 2020 17:15:00
Message: <web.5e5e8fe25f4031dc2e40bb200@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> So, basically you want something like this:

Yes, to some extend, I like what I see. :-)

There are the ropes on the left side of the vertical cylinder, and those on the
right side. All twist around the horizontal arm. The ropes of the one side
(let's say left) are ABOVE the ropes of the right side.

Would you allow me to give you credit inside the scene file?


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