On Thu, 29 Mar 2001 14:09:54 +0100, Tom Melly wrote:
>"D. Stark - eSN" <dms### [at] esupportnowcom> wrote in message
>news:3AC32A66.14D83985@esupportnow.com...
>> Today's Astronomy Picture of the Day is some awesome aurora.
>>
>
>... with a fractal like shape at the bottom of the pic.

Those'd be trees.  Methinks you need to get out more. :)

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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"Ron Parker" <ron### [at] povrayorg> wrote in message
news:slr### [at] fwicom...
> >
> >... with a fractal like shape at the bottom of the pic.
>
> Those'd be trees.  Methinks you need to get out more. :)
>

LOL

Um, ah, I knew that, really, honest. What? Trees aren't fractal?

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I saw this picture on the CNN site, thought it might help.

Kirk

"Gail Shaw" <gsh### [at] monotixcoza> wrote in message
news:3ac07177@news.povray.org...
> I decided I needed some atmospheric effects for my
> irtc entry (which I will post once it's more than a few cylinders
> and cones)
>
> This is supposed to be the aurora borealis.  It's an isosurface
> containing media with a function used in the density.
>
> For those who live far enough north to see the real thing, does
> it look right?
>
> For the iso experts, is there any way I can randomly vary the
> distance between the peaks of a sine wave?
>
> Comments? suggestions?
>
> Gail
> *************************************************************************
> * gsh### [at] monotixcoza                *   Step into the abyss,           *
> * http://www.rucus.ru.ac.za/~gail/   *   and let go.        Babylon 5   *
> *************************************************************************
> * The difficult we do immediately, the impossible takes a little longer *
> *************************************************************************
>
>
>

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Attachments:
Download 'aurora.jpg' (20 KB)

Preview of image 'aurora.jpg'

Gail Shaw wrote:
> 
> And version 3. It's amazing what a little
> turbulence does.
> 
> I'm also working on a red and yellow aurora, but it doesn't
> look so good.
> 
> Comments?

Now you're getting somewhere. I've been working with norhtern lights
infotainment for about 6 years, and I also grew up in an area where
northern lights where more the rule than the exception during cold
winter nights. 

One thing to remember about aurora is that it is almost always curling
across the sky, not in one sheet, but in curls as seen in many of the
pictures of actual auroras in this thread.

If you want to add yellow or red, it should be very subtle and at the
higher reaches of the aurora. It is very rarely seen, and it's almost
always overpowered by the green in the aurora.

The green in the aurora is also very light green, not as saturated green
as you have it. If you notice the images posted by Jari Juslin you can
see that the aurora is curling across the sky, and that the color is
dense at the bottom of the aurora almost greenish white, and it fades to
almost translucent towards the top. You will also notice that the aurora
is almost whiteish green at the bottom and the green is getting more
saturated at the top.

I've seen auroras with orange, blue and yellow colors, but always
intermixed with the ever present green.

Oh, well, I am rambling here. What I am saying is that it's close, but
no cigar yet. ;-) Keep working on it though!

-- 

------------------------------------------------------------------------
  +47 90 62 71 78          DoD#2101, DoDRT#017, NIC#015, PJ#006, OGM#007
  azo### [at] dodno, Ducati M600, Clementine  Ubesudlet: Aldri eid en J&%#PS.

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Trees -are- fractal.

Tom Melly wrote:
> 
> "Ron Parker" <ron### [at] povrayorg> wrote in message
> news:slr### [at] fwicom...
> > >
> > >... with a fractal like shape at the bottom of the pic.
> >
> > Those'd be trees.  Methinks you need to get out more. :)
> >
> 
> LOL
> 
> Um, ah, I knew that, really, honest. What? Trees aren't fractal?

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These auroras are great to see, whether real or not.
I'm chiming in a bit late but I tried to create one using just media with
multiple density maps inside a box, not Gail's isosurface way.
I have only seen one in my whole life (long time) but it was everything from
a large diffuse red glow overhead to start with then changing to curtains
and finally rays.  Something everyone should be witness to at least once,
like me.
Attached is my trial and error and giving up on it now. Might make a nice
nebulosity anyhow, but there's already an include for that.

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Attachments:
Download 'abmedia5.jpg' (14 KB)

Preview of image 'abmedia5.jpg'

In article <3ac48209@news.povray.org>, Bob H. says...
> These auroras are great to see, whether real or not.
> I'm chiming in a bit late but I tried to create one using just media with
> multiple density maps inside a box, not Gail's isosurface way.
> I have only seen one in my whole life (long time)
long?? 52 = long???

> but it was everything from
> a large diffuse red glow overhead to start with then changing to curtains
> and finally rays.  Something everyone should be witness to at least once,
> like me.
> Attached is my trial and error and giving up on it now. Might make a nice
> nebulosity anyhow, but there's already an include for that.
> 

ha, ha,
-- 
Regards,  Sander

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Today it's at:
http://antwrp.gsfc.nasa.gov/apod/ap010329.html

Kind of serendipitous ....

        == John ==

"D. Stark - eSN" <dms### [at] esupportnowcom> wrote in message
news:3AC32A66.14D83985@esupportnow.com...
> Today's Astronomy Picture of the Day is some awesome aurora.
>
> http://antwrp.gsfc.nasa.gov/apod/astropix.html
>
>
>
> --
> Derek Stark
> Linux Admin - eSN
> dms### [at] esupportnowcom
> xt 8952

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Hope this isn't a repeated web address:

http://www.pfrr.alaska.edu/~pfrr/AURORA/INDEX.HTM

Has a great prediction map you can select your own region from for northern
latitudes:

http://www.gi.alaska.edu/aurora_predict/worldmap8.html

There's a current maximum going on because of a recent solar flare.

A "raytraced" aurora at the originating web page (don't know what it was
raytraced with but looks POVish to me):

http://www.geo.mtu.edu/weather/aurora/

Click on the jpg link to enlarge it.

Bob H.

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"Bob H." <omn### [at] msncom> wrote in message
news:3ac532c8$1@news.povray.org...
> Hope this isn't a repeated web address:
>
> http://www.pfrr.alaska.edu/~pfrr/AURORA/INDEX.HTM
>
> Has a great prediction map you can select your own region from for northern
> latitudes:
>
> http://www.gi.alaska.edu/aurora_predict/worldmap8.html
>
> There's a current maximum going on because of a recent solar flare.
>
> A "raytraced" aurora at the originating web page (don't know what it was
> raytraced with but looks POVish to me):
>
> http://www.geo.mtu.edu/weather/aurora/
>
> Click on the jpg link to enlarge it.
>

Add this one:

 http://www.spaceweather.com/aurora/gallery_20mar01.html

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