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18 Nov 2024 10:21:05 EST (-0500)
  Twisty Wires and long sparks. (Message 1 to 10 of 10)  
From: Dave VanHorn
Subject: Twisty Wires and long sparks.
Date: 15 May 2004 18:11:41
Message: <40a6959d@news.povray.org>
I'm using pov to do some mechanical planning for a project.
It's two towers of identical capacitors and spark gaps, fed with a ladder of
resistors.

When the spark gaps fire, they change the capacitor connections from
parallel to series, and in this case, multiply the voltage from 10,000V to
100,000V on each tower.  The towers will be set opposite, so that one goes
from +10kV to +100kV, and the other goes from -10kV to -100kV, making the
potential across the tops 200kV.

What I need now (other than some real textures) :) is a way to do some
realistic wires.
The wires connect the spark gaps (brass doorknobs) to the ends of the
capacitors.
On any given gap, the left knob connects to the left lower cap terminal, and
the right one connects to the right upper cap terminal, so that the spark
gaps can be thought of as being connected diagonally across the
capacitor/resistor ladder.

I'm not seeing how to make the wires since they need complex curves that I
can't easily define mathematically.



-- 
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet?


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marxdetail.JPG


 

From: Alain
Subject: Re: Twisty Wires and long sparks.
Date: 16 May 2004 09:52:47
Message: <40a7722f$1@news.povray.org>
Dave VanHorn nous apporta ses lumieres ainsi en ce 2004/05/15 18:12... :

>I'm using pov to do some mechanical planning for a project.
>It's two towers of identical capacitors and spark gaps, fed with a ladder of
>resistors.
>
>When the spark gaps fire, they change the capacitor connections from
>parallel to series, and in this case, multiply the voltage from 10,000V to
>100,000V on each tower.  The towers will be set opposite, so that one goes
>from +10kV to +100kV, and the other goes from -10kV to -100kV, making the
>potential across the tops 200kV.
>
>What I need now (other than some real textures) :) is a way to do some
>realistic wires.
>The wires connect the spark gaps (brass doorknobs) to the ends of the
>capacitors.
>On any given gap, the left knob connects to the left lower cap terminal, and
>the right one connects to the right upper cap terminal, so that the spark
>gaps can be thought of as being connected diagonally across the
>capacitor/resistor ladder.
>
>I'm not seeing how to make the wires since they need complex curves that I
>can't easily define mathematically.
>
>
>
>  
>
Have you tried using sphere_sweep with b_spline or cubic_spline for your 
wires? You set some control points and the sphere sweeps smoothly from 
one to the other. You need 2 extra, purely controll, points, one at each 
end of the sweep, and you can have as many other points as you want.

Alain


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From: Dave VanHorn
Subject: Re: Twisty Wires and long sparks.
Date: 16 May 2004 09:58:00
Message: <40a77368$1@news.povray.org>
> Have you tried using sphere_sweep with b_spline or cubic_spline for your
> wires? You set some control points and the sphere sweeps smoothly from
> one to the other. You need 2 extra, purely controll, points, one at each
> end of the sweep, and you can have as many other points as you want.
>
> Alain

Not sure how to begin with it.

Sparks are a bit "jaggy", and of course very bright.

I also have to solve the problem of wires, which do smooth (and complicated)
curves.


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From: Alain
Subject: Re: Twisty Wires and long sparks.
Date: 16 May 2004 16:36:01
Message: <40a7d0b1@news.povray.org>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
  <title></title>
</head>
<body>
Dave VanHorn nous apporta ses lumieres ainsi en ce 2004/05/16 09:58...
: <br>
<blockquote cite="mid40a77368$1@news.povray.org" type="cite">
  <blockquote type="cite">
    <pre wrap="">Have you tried using sphere_sweep with b_spline or cubic_spline for
your
wires? You set some control points and the sphere sweeps smoothly from
one to the other. You need 2 extra, purely controll, points, one at each
end of the sweep, and you can have as many other points as you want.

Alain
    </pre>
  </blockquote>
  <pre wrap=""><!---->
Not sure how to begin with it.

Sparks are a bit "jaggy", and of course very bright.

I also have to solve the problem of wires, which do smooth (and complicated)
curves.


  </pre>
</blockquote>
sphere_sweep with b_spline for the wires. This enable you to do very
complicated and smooth 3D curves. An example of a sphere_sweep using
b_spline interpolation. A total of 34 random points were used.<br>
<img height="300" width="400" alt=""
 src="cid:par### [at] qwertygov"><br>
You want a or some electric sparks going from one knob to the other,
you can use some emissive media with a good amount of turbulence. Have
a sharp color_map blue-white in the middle, clear everywhere else,
turbulent cylindrical pattern, add some other small dimer tighter media
to do some forking. Render using radiosity and the sparks will light up
your cene.<br>
<br>
<br>
Alain<br>
</body>
</html>


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From: Dave VanHorn
Subject: Re: Twisty Wires and long sparks.
Date: 17 May 2004 00:58:16
Message: <40a84668$1@news.povray.org>
You want a or some electric sparks going from one knob to the other, 
you can use some emissive media with a good amount of turbulence. Have a 
sharp color_map blue-white in the middle, clear everywhere else, 
turbulent cylindrical pattern, add some other small dimer tighter media 
to do some forking. Render using radiosity and the sparks will light up 
your cene.

  Ok, I got this far, but I get an error when I run: Attempt to malloc 
zero size block

  #declare Spark1 = object { sphere_sweep { b_spline,
                                            3, //NUM_OF_SPHERES,
                                            <-0.5, 0.0, 0.0>, 0.001 
//CENTER, RADIUS,
                                            < 0.0, 0.5, 0.5>, 0.01
                                            < 0.5, 0.0, 0.0>, 0.001
                                          }
                             scale <(1 * Inch), (1 * Inch), (1 * Inch)>
                           }


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From: Dave VanHorn
Subject: Re: Twisty Wires and long sparks.
Date: 17 May 2004 00:58:16
Message: <40a84668$3@news.povray.org>
Ok, I see now that it takes at least four points, and I have it working 
sort of. 

Now, how to make the spark look real, and illuminate it's surroundings.

I'll probably need an inner spark in white, and a diffuse outer sheath 
in violet.


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From: Ben Udal
Subject: Re: Twisty Wires and long sparks.
Date: 21 May 2004 01:09:00
Message: <40ad8eec$1@news.povray.org>
A Marx Generator!
I'm trying to build a small one of those myself.  There are some good 
pictures at Mike's Eletric Stuff

http://www.electricstuff.co.uk/marxthree.html

-Ben

Dave VanHorn wrote:
> I'm using pov to do some mechanical planning for a project.
> It's two towers of identical capacitors and spark gaps, fed with a ladder of
> resistors.
> 
> When the spark gaps fire, they change the capacitor connections from
> parallel to series, and in this case, multiply the voltage from 10,000V to
> 100,000V on each tower.  The towers will be set opposite, so that one goes
> from +10kV to +100kV, and the other goes from -10kV to -100kV, making the
> potential across the tops 200kV.
> 
> What I need now (other than some real textures) :) is a way to do some
> realistic wires.
> The wires connect the spark gaps (brass doorknobs) to the ends of the
> capacitors.
> On any given gap, the left knob connects to the left lower cap terminal, and
> the right one connects to the right upper cap terminal, so that the spark
> gaps can be thought of as being connected diagonally across the
> capacitor/resistor ladder.
> 
> I'm not seeing how to make the wires since they need complex curves that I
> can't easily define mathematically.


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From: Dave VanHorn
Subject: Re: Twisty Wires and long sparks.
Date: 21 May 2004 09:57:10
Message: <40ae0ab6$1@news.povray.org>
"Ben Udal" <ben### [at] niftythingsorg> wrote in message
news:40ad8eec$1@news.povray.org...
> A Marx Generator!
> I'm trying to build a small one of those myself.  There are some good
> pictures at Mike's Eletric Stuff
>
> http://www.electricstuff.co.uk/marxthree.html

So what do you think of my images?

The real caps on hand, are 0.05uF 10kV, but I can buy larger from a chinese
supplier.


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From: Ben Udal
Subject: Re: Twisty Wires and long sparks.
Date: 23 May 2004 03:19:45
Message: <40b05091$1@news.povray.org>
Dave VanHorn wrote:
> "Ben Udal" <ben### [at] niftythingsorg> wrote in message
> news:40ad8eec$1@news.povray.org...
> 
>>A Marx Generator!
>>I'm trying to build a small one of those myself.  There are some good
>>pictures at Mike's Eletric Stuff
>>
>>http://www.electricstuff.co.uk/marxthree.html
> 
> 
> So what do you think of my images?
> 
> The real caps on hand, are 0.05uF 10kV, but I can buy larger from a chinese
> supplier.

Your "Big Whopping Sparks" image is looking really nice.  The spark 
technique you've used creates a very pleasing effect.  The only thing 
that's really bothering me is the plexiglass material.  The numerous 
reflections made it hard for me to figure what exactly I was looking at. 
  But other than that, you've made some excellent progress and I look 
forward to seeing the final image.

Heh, your caps are considerably larger than mine.  I settled on 0.0047uF 
10kV ones for my design and they were expensive enough as it is :)  If 
you don't mind me asking, where did you get your caps.  Larger ones 
might be useful in the future and they're harder to find than most 
components.

-Ben


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From: Dave VanHorn
Subject: Re: Twisty Wires and long sparks.
Date: 23 May 2004 12:34:36
Message: <40b0d29c$1@news.povray.org>
> Your "Big Whopping Sparks" image is looking really nice.  The spark
> technique you've used creates a very pleasing effect.  The only thing
> that's really bothering me is the plexiglass material.  The numerous
> reflections made it hard for me to figure what exactly I was looking at.
>   But other than that, you've made some excellent progress and I look
> forward to seeing the final image.

I'm not really pleased with that yet, and it has no refraction at the
moment, but that's a minor issue.


> Heh, your caps are considerably larger than mine.  I settled on 0.0047uF
> 10kV ones for my design and they were expensive enough as it is :)  If
> you don't mind me asking, where did you get your caps.  Larger ones
> might be useful in the future and they're harder to find than most
> components.

These particular ones I got at the Dayton Hamfest for $1 each.  23 of them
in a tub.
I've charged them all to 10kV, no failures. :)

I have a source in China for larger voltage/C values, but getting some
actually here is proving difficult.  It's easy to buy a containerload, hard
to buy 10's.


> -Ben


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