Unsatisfied with the appearance of gstars in Celestia (1.6.2.2 and earlier)

Tips for creating and manipulating planet textures for Celestia.
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Goofy
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Unsatisfied with the appearance of gstars in Celestia (1.6.2.2 and earlier)

Post #1by Goofy » 06.06.2021, 13:49

Hi.
I never liked how gstars were shown in Celestia, so I tried to make a new texture,using real Sun images and Pshop filter gallery, in the search of a way to show granulation and spots.
This is the 2k result, reduced to 1k to show it here, and I was satisfied of it.
I suggest you to open the image :smoke:

My-gstar.jpg


But when I used it in Celestia (any version till 1.6.2.2 and any render) the result was completely different, and ugly... :boxing:

My-gstar-in-celestia.jpg


I'm unaware of a lot of things regarding textures and their realization, so I supposed that the image shown in Celestia had to be very close to the original, but it wasn't so. :insane:
Please someone explainin me where I'm wrong, and how can I correct it.
Thanks a lot.

Goofy :help:
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trappistplanets
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Post #2by trappistplanets » 06.06.2021, 14:43

you can try using these instead https://sdo.gsfc.nasa.gov/assets/img/browse/
and there should be an offset and a polar coordinate filter you can use to fix polar seams (polar pinching) and other kind of seams
look at FarGetaNick's g star texture for refrence for a realistic color
and please press Shift+5, that will give you the realistic black body colors you see in real stars, g stars are not that yellow, there white

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Post #3by Goofy » 06.06.2021, 16:37

Thank you, but you misundertstood my question, surely my fault due to my poor English.
I'm not searching for other gstar textures (better or worst), and I'm not worrying of pole pinch (I know how to remove it, and I'll do,later on), I'm pretty satisfied with my image (it's a matter of taste, you know, every one prefers something different, don't you?).
I'm simply asking for an explanation of the reason why my image looks so different when seen in Celestia, it's only a matter of overall appearance.
Regarding the yellow color, I agree with you, but with a brighter and whiter tone the granulation almost vanishes out, as you can see here, compared with the previous one:

My-gstar-clear.jpg

My-gstar.jpg


Anyway, just to be even more clear about personal taste and so on, this is the "official" Celestia gstar image from a lot of time.

Celestia-gstar.jpg


Just one comment: the contemporary presence of (enormous!) sunspots near both equator and poles is impossible, so the actual image is not so perfect as it should, IMHO.
Hope to have been clear enough this time.
Bye
Goofy :smile:
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Eric Nelson
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Post #4by Eric Nelson » 06.06.2021, 18:04

For your information, G-stars are meant to look almost white (with only subtle hints of yellow or gold).
Those colorful images of Sol (or our Sun) you see in space photos are false-colored and based on radiation like ultraviolet or X-rays.

And when we see sunrise or sunset, our star looks yellow-orange or red due to the Rayleigh mie scattering in Earth's atmosphere.
Even our Moon and such look such vibrant colors near the horizon for the exact same reason.

In fact, G-stars like Sol are very bright yellow/gold-white and not orange like stars halfway between the K and M spectrum.
This yellow-orange texture looks like a star halfway between the K and M spectrum.
Sol and other G stars are much closer to white in reality than yellow-orange.
Celestia got the star colors right after all and the Celestia Origin star textures are especially excellent.
Last edited by Eric Nelson on 29.06.2021, 14:19, edited 2 times in total.

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Post #5by Goofy » 06.06.2021, 18:35

Thank you for the astronomy lesson, Eric, but it's useless, given I'm a teacher. :wink:
But my question remains the same and, alas, unreplied and so unresolved.
I repeast it, just to be clear (I hope):
why the texture in my first post shows so differently in Celestia? :insane:
Bye.
Goofy :smile:
"Something is always better than nothing!"
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Eric Nelson
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Post #6by Eric Nelson » 06.06.2021, 18:41

Star textures look different on Celestia due to the atmospheric glow around the stars.
A yellow-orange star texture will look lemon-yellow on Celestia unless you select the star style to scaled discs.
The atmosphere color of stars are different from the yellow-orange color of this star texture.
That's just the way it is.

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Sirius_Alpha
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Post #7by Sirius_Alpha » 06.06.2021, 18:46

The "flare" overlaid on top of the base texture brightens it a lot within Celestia. You will need to dim the actual texture to compensate for that to make it look closer to what you want it to in Celestia. At least how I've understood your question.

For everyone else in this thread: Please try reading the OP and replying to the point of his message. His post was not an invitation to take the thread off-topic and recommend star textures, or give basic lessons in astronomy. People don't make posts asking a question in this forum because they want to engage in an unrelated conversation about personal tastes.
Exoplanet nerd. I maintain a monthly-updated exoplanet catalogue here:
https://celestia.space/forum/viewtopic.php?f=23&t=18705

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Goofy
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Post #8by Goofy » 06.06.2021, 19:50

Thanks you both, I had some doubt about atmospheric glow, but the scaled disks information solved the problem perfectly, as you can see in the following image:

My-gstar-scaled-disks.jpg


This means that easily and quikly I can change Sun image appearance just inserting in script the starstyle setting change command when needed. :clap:
Previously I was thinking that the command could change only the pointlike appearance of far away stars, not the texture rendering too.
My fault! :oops:
Now I can brighten the image and remove a lot of yellow saturation, and the result will be more realistic when showing granulation.
Thanks a lot!
Bye

Goofy :smile:
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Eric Nelson
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Post #9by Eric Nelson » 06.06.2021, 21:21

Yup, and it's always good and helpful to let others learn regardless.

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trappistplanets
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Post #10by trappistplanets » 07.06.2021, 00:49

Goofy wrote:I'm simply asking for an explanation of the reason why my image looks so different when seen in Celestia, it's only a matter of overall appearance.
could be the star's glow and texture brightness,
you will have the best result with this texture you made
download/file.php?id=10576&filename=My-gstar-clear.jpg&mode=view
it is the closes to the generic g star texture in color and brightness, so it should give you the best result your looking for

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Post #11by Goofy » 07.06.2021, 10:27

Thank you trappistplanets, I'll do it.
Bye
Goofy :smile:
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