Earth Night (64K)

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Alexell M
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#1by Alexell » 17.03.2017, 17:07

earthnight.png


Author: RVS
Description: Improved and modernized map of the night side of the Earth (lores, medres and hires).
Installation: extract into Celestia folder.
Attachments
new_earthnight.zip
(47.22 MiB) Downloaded 105 times
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scalbers
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#2by scalbers » 17.03.2017, 17:34

For fun I can mention some simulations I've been done for the Earth at night, as in this image.

muri_790km.png


VIIRS data is pretty good for night lights info. It is tricky to avoid saturating the bright areas. I wonder if Celestia can have a slider bar to adjust the brightness, so we can use 32-bit images that have the full dynamic range? There is also airglow and some twilight showing up in this view from 800km altitude. The colors of the lights are also a bit subjective, though generally it should be a yellowish white color, Perhaps more white in city centers where white LED lights are rapidly being installed. This is changing year by year. Zodiacal light shows in the upper right.

Clouds can be added that would have a blurring effect on the lights, and might darken them if the clouds are on the thick side.
Last edited by scalbers on 17.03.2017, 18:07, edited 1 time in total.
http://stevealbers.net

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#3by FarGetaNik » 17.03.2017, 17:52

scalbers wrote:wonder if Celestia can have a slider bar to adjust the brightness, so we can use 32-bit images that have the full dynamic range?

I would love to have that. I only really makes sense if Celestia displayed brightness realistically though. Stars are too dim, night lights too bright...
Do I see some airglow in your image? Don't make me jealous. Your renders are fantastic!

Regarding the addon, I'm using the very same data, but png textures. At first I much appreacciated the smaller size of dds (for some reason I can't open these dds images, but Celestia handles them just fine). But just extracting the addon into extras won't install it. It was a pain to add it to my installation, mostly because I accidently dumped all the files into my previous earth-night directory. This was because the folder here is named "earth-night", everything else "earthnight", so I expected a different name for the folder as well. I won't use it, I don't like such bright lights. This is me personally though, the addon quality is still great.

scalbers
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#4by scalbers » 17.03.2017, 18:05

Indeed the night lights of big cities seen up close would be quite a bit brighter than stars. They could I think be displayed realistically and then the slider bar would be able to brighten the image to show the stars well (burning in the cities) or dimmed to show mostly just the large city lights. Smaller cities would be more comparable to the stars.

Generally airglow is dimmer than the urban lights and the twilight is brighter as well.

I took the first step of downloading the Celestia source code so I can gradually start to learn how it works.
http://stevealbers.net

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#5by FarGetaNik » 17.03.2017, 18:58

scalbers wrote:Indeed the night lights of big cities seen up close would be quite a bit brighter than stars.

What bothers me is the relative brightness of sun-lit Earth vs. night lights:

Earth-nightlights.jpg


Using my already dimmed texture (128 counts is brightest). Looks fine to me, but in reality it would be even darker I believe. Though I can easily imagine when in low Earth orbit, the apparent brightness could exceed the brighest stars still.

scalbers
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#6by scalbers » 17.03.2017, 19:19

If you're saying the sun-lit Earth should be brighter relative to the night lights I would agree. Without the slider bar though I can understand why sometimes HDR type techniques would be used to even things out, even if it isn't that realistic.

Another way to think of this is if you are in orbit and your eyes are adapted to look at the bright daylight part of the Earth you wouldn't be able to see any but the very brightest stars. As the move away from Earth and the angular diameter shrinks the stars would get somewhat more visible. This would depend on how well you can shield the Earth-light from your visual field. For the same phase and angular size, the Earth should be around 3 times as bright as the moon.

Getting back to the first post I've heard that John Van Vliet has also made a colorized night light texture for Celestia.
http://stevealbers.net

Alexell M
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#7by Alexell » 19.03.2017, 20:55

scalbers, If you study and understand how rendering in Celestia works, your contribution will be invaluable! :clap:
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#8by scalbers » 19.03.2017, 21:37

Thanks Alexell, I hope I can learn more about C++, shaders, and the Celestia code in my allotment of spare time.

I see a glow around the sun when running Celestia, so is this how the corona is currently handled? Where is this set? This could maybe tie into the zodiacal light.
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#9by Alexell » 20.03.2017, 07:48

scalbers, Most likely the glow is described in nearstars.stc

Code: Select all

0 "Sol:Sun"
{
   OrbitBarycenter "Solar System Barycenter"
   CustomOrbit "vsop87-sun"

   SpectralType "G2V"
   AbsMag 4.83

   UniformRotation
   {
       Period         609.12  # 25.38 days
       Inclination      7.25
       AscendingNode   75.77
       MeridianAngle   23.00  # standard meridian
   }
}


Added after 2 minutes 8 seconds:
Although it may not. Perhaps the glow is described in the code and for all stars the same, only the color differs depending on the spectral class.
I just know that there are addons that change the color of this glow from the Sun and strengthen it.
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FarGetaNik M
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#10by FarGetaNik » 20.03.2017, 08:32

The "glow" of the sun is sometimes modified with an atmosphere, not actually modifying the star color. When further away, the glow doesn't seem to scale, it's more like an overexposure due to luminosity. When close to the sun, the "atmoshpere" (corona) shows up. This seems to be universally for all stars, so it must be configurated somewhere in the source code.

John Van Vliet
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#11by John Van Vliet » 20.03.2017, 22:41

i did make one a few years back from the viirs imaging
see the celestialmatters forum
http://forum.celestialmatters.org/viewtopic.php?f=9&t=451&start=0
and
http://forum.celestialmatters.org/viewtopic.php?f=9&t=606

youtube - 1080
https://youtu.be/ArOI4QCLMXA

https://youtu.be/-kYH2kUuiVQ

removing the cloud noise and moon glow and detector noise was a pain in the rear

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#12by FSword7 » 09.10.2017, 23:02

I think that problem is only one color for entire night light textures. I had seen some ISS pictures showed that colorful night lights (not only yellow but some blue (LED lights), green, and others).

John Van Vliet
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#13by John Van Vliet » 10.10.2017, 04:32

i hand painted the lights based on orbital imaging at the CITY level

so they are NOT all the same color

a quick old VS new
level4 tx_8_4.png 512x512 vt tile
OldNew.png


and my home town
Screenshot_20171010_003906.png


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