I have been using this basic formula below...

min(1,pow(exp(_base_scale_radius-_atm_scale_radius*sqrt(x*x+y*y+z*z)),
_hh_gamma))

First (hidden) parameter is the "Scale Height"... that is the height above
the surface of the planet where the atmospheric density changes by a factor
of e.  (E is 2.718281828...) and is generated by fancy trigonometric
operations.  In POV-Ray, it's exp(1).  In this formula, I set "base scale
radius" to be about 32 * scale height below the surface of earth, and I set
"atm scale radius" to be 32 * scale height above the surface of earth.  I
use "Scale Height" because when you do the research, information is
available... for earth, the scale height is 8.5 km.  A rocket going
straight up when reaching 8.5 km in the sky will experience a pressure of
(surface)*e^(-1), which is about 300 mbars.

However, in POV-Ray, this function may seem broken when applied to shooting
beams through media (atmosphere).  To correct it, I apply a gamma of e.
This seems to correct a bunch of things.

So.. just experimenting with some parameters and colors, I produced this
image...

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Attachments:
Download 'asia june 2006.jpg' (426 KB)

Preview of image 'asia june 2006.jpg'

If the terminis was a little sharper it would look perfecto.

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Halbert <hal### [at] gmailcom> wrote:
> If the terminis was a little sharper it would look perfecto.
>


Yeah, I know what you mean... it's extremely tricky getting the parameters
right.  For each parameter I input that produces a good scene, I can
generate another scene that will make it look bad.

Yet, I found some sample photos that shows I'm actually not very far from
the perfect scene render.

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Hmmm... Hmmmmmm.....

Hmm! I like it a lot! I think, you actually got a better atmosphere than I 
got previously. I think, most of it can be kept this way. Maybe (just my 
opinion) the atmosphere is just a little bit too bright. I would suggest to 
reduce the brightness or ambient (or gamma) value a little bit. Please see 
again the attached photo of the atmosphere. However, the appearance of the 
atmosphere might differ in dependency from the distance to Earth, I believe. 
Due its brightness it looks too sharp. That would be what I would give a try 
to, if I had the entire source code for the atmosphere. Would you consider 
to publish it?

But besides that, I really think I would prefer your atmosphere to my own 
one.

Best greetings,

Sven

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Attachments:
Download 'Planet.jpg' (100 KB)

Preview of image 'Planet.jpg'

"Sven Littkowski" <sve### [at] jamaica-focuscom> wrote:
> Hmmm... Hmmmmmm.....
>
> Hmm! I like it a lot! I think, you actually got a better atmosphere than I
> got previously. I think, most of it can be kept this way. Maybe (just my
> opinion) the atmosphere is just a little bit too bright. I would suggest to
> reduce the brightness or ambient (or gamma) value a little bit.

Yeah, I blew it up purposely.  It's really tricky.  Reducing the brightness
will also reduce the haze, making the surface look too clear.

> Please see
> again the attached photo of the atmosphere.

I've seen this before... Is this a photo or a render?

> However, the appearance of the
> atmosphere might differ in dependency from the distance to Earth, I believe.
> Due its brightness it looks too sharp. That would be what I would give a try
> to, if I had the entire source code for the atmosphere. Would you consider
> to publish it?

Sure.. I would like to publish it.... be ware that it's still in a quite
volatile state, even after working on it for more than a year already.  As
soon as I publish it, it will be modified again.

Now where do I upload it to?  There are so many confusing forums to login to
and I don't want to upload it to the wrong site.

>
> But besides that, I really think I would prefer your atmosphere to my own
> one.

I'm quite flattered... and would like to work together with you so that we
can perfect our renders.

Here is "/include/EagleSun/worlds.inc"

Here's a challenging sample...

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Attachments:
Download 'gpw-20050916-nasa-sts093-708-37-atlantic-ocean.jpg' (97 KB)

Preview of image 'gpw-20050916-nasa-sts093-708-37-atlantic-ocean.jpg'

Uihh! That render is great!


"EagleSun" <nomail@nomail> schrieb im Newsbeitrag 
news:web.44863a26e4051eaccfb0a3d70@news.povray.org...
> I've seen this before... Is this a photo or a render?
A photo. That's why I take this as target of what I want to re-create in my 
renders.

> Now where do I upload it to?  There are so many confusing forums to login 
> to
> and I don't want to upload it to the wrong site.
One of these newsgroups here, probably this one: 
"povray.binaries.scene-files".

> I would like to work together with you so that we can perfect our renders.
Sure! Great! Anytime! Let's work out now, how.

> Here is "/include/EagleSun/worlds.inc"
Where?

Best greetings,

Sven

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"Sven Littkowski" <sve### [at] jamaica-focuscom> wrote:
> Uihh! That render is great!

Whoah!  *blush* that's not a render... it's a photo to give us a challenge.

> > Now where do I upload it to?  There are so many confusing forums to login
> > to
> > and I don't want to upload it to the wrong site.
> One of these newsgroups here, probably this one:
> "povray.binaries.scene-files".

OK... I'll upload there... though not sure how a Pov source can be
considered a "binary"...

> > I would like to work together with you so that we can perfect our renders.
> Sure! Great! Anytime! Let's work out now, how.
>
> > Here is "/include/EagleSun/worlds.inc"
> Where?

OOPS!  what I mean is that I'll upload it once I know where to upload it
to... I had a dream last night that will simplify the source code.  I'm
doing a few QA renders then I'll upload it.  Look for it before 15:00 UTC
today at povray.binaries.scenes-files.

Hmm... I almost clicked on [Send] and before I clicked, I noticed a QA
render is doing quite well...

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"EagleSun" <nomail@nomail> wrote:

> > > Here is "/include/EagleSun/worlds.inc"

> Look for it before 15:00 UTC
> today at povray.binaries.scenes-files.

I just posted it there...

Here's part of "solarsys.pov" that will render Earth.

global_settings {
 max_trace_level 20
 assumed_gamma 1.0
 ambient_light 0
/* radiosity {
  brightness 1/32
  media on
  normal on
  count 1000
 // pretrace_start 1/16
 // pretrace_end 1/128
 }*/
}

#include "EagleSun/worlds.inc"

#declare sun_radius = 695000;

#declare venus_distance = 108200000;

#declare earth_distance = 149600000;
#declare moon_distance = 384401;

#declare mars_distance = 227940000;

#declare jupiter_distance = 778330000;

#declare saturn_distance = 1429400000;

#declare uranus_distance = 2870990000;

#declare neptune_distance = 4504300000;



#macro Earth(_distance, _hour, _year, _heading, _pitch, _bank)
 SunLight(earth_distance, sun_radius, rgb 1, 10, _heading, _pitch, _bank)
 #local _albedo=0.39; // Map is already adjusted for albedo.
 #local _radius=6370;
 #local _tilt=23.45;
 #local _tiltshift=354/365.25;
 object {
  LandSurface(_radius, 8.85, 0, _albedo, jpeg_type, "Solar
System/Earth/EarthMap_2500x1250.jpg", jpeg_type, "Solar
System/Earth/EarthElevation_2500x1250.jpg")
  TransformWorld(_distance, _hour, _year, _heading, _pitch, _bank, _tilt,
_tiltshift)
 }
 object {
  Clouds(_radius, 9, 1, jpeg_type, "CloudMaps/EarthClouds_2500x1250.jpg",
rgbt 1, rgb 1)
  TransformWorld(_distance, _hour+1, _year, _heading, _pitch, _bank, _tilt,
_tiltshift)
 }
/* object {
  Atmosphere(_radius, 8.5, 91/255, 117/255, 192/255, 32/65535, 1, 0)
  TransformWorld(_distance, _hour, _year, _heading, _pitch, _bank, _tilt,
_tiltshift)
 }
 object {
  Atmosphere(_radius, 0.75, 173/255, 186/255, 224/255, 96/65535, 2.71828, 0)
  TransformWorld(_distance, _hour, _year, _heading, _pitch, _bank, _tilt,
_tiltshift)
 }*/
 object {
  Atm2Sphere(_radius, 8.5, 32/255, 53/255, 145/255, 0.008, 1, 3, 91/255,
117/255, 192/255, 0.115, 1)
 // AtmSphere(_radius-0.01, 8.5, 91/255, 117/255, 192/255, 0.015, 0.25)
  TransformWorld(_distance, _hour, _year, _heading, _pitch, _bank, _tilt,
_tiltshift)
 }
#end


Stars_Crackle(105, 0, 30)
Earth(0, 16, 0.75, 105, 0, 30)
TerragenViewFrom(1, 6370*2.5, 0, 0, 0)

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High!

EagleSun wrote:

> So.. just experimenting with some parameters and colors, I produced this
> image...

Great weather in Afghanistan... except for some thunderheads over 
Nangarhar and Kunar province (which are usual in summer)! Minimalist 
Khyberspace in a way...

See you there!

Yadgar

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