planet texture license? and milkyway texture

Tips for creating and manipulating planet textures for Celestia.
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aardwolf
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planet texture license? and milkyway texture

Post #1by aardwolf » 15.10.2005, 14:03

Hi, I'm making a computer game that is a space game and I need textures for all planets of the solar system, the sun and the milkyway.

I discovered Celestia has very nice textures of all those planets. Are those textures public domain? Can I use them for my spacegame? Are there any restrictions?

Thanks!

Oh and I didn't find a good milkyway texture yet. So I crafted one myself, but it's very ugly. Does anyone know a milkyway texture that would generate a result like the "drool" image?

Here's a screenshot of the game and the ugly milkyway texture (click on it to resize):

Image

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Post #2by Boux » 17.10.2005, 16:30

Hi,
If it's for a computer game, then perhaps you need not an absolutely scientifically exact texture of the Milky Way.
You may want to try playing with the 2MASS pictures there:
http://photojournal.jpl.nasa.gov/catalog/PIA04250
... to extract the side view of the galaxy and build something looking like what you are looking for. This would require a lot of Photoshop work obviously, but would not be unachievable.
Obviously, if you plan a public release in the future, then you certainly would have to get some copyright clearance from the owners (or better, get also from them a better resolution original).
I am just curious, is this a skybox kind of rendering or a texture mapped on the inner side of a sphere?
Good luck 8)

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Post #3by aardwolf » 18.10.2005, 10:47

Boux wrote:Hi,
If it's for a computer game, then perhaps you need not an absolutely scientifically exact texture of the Milky Way.
You may want to try playing with the 2MASS pictures there:
http://photojournal.jpl.nasa.gov/catalog/PIA04250
... to extract the side view of the galaxy and build something looking like what you are looking for. This would require a lot of Photoshop work obviously, but would not be unachievable.
Obviously, if you plan a public release in the future, then you certainly would have to get some copyright clearance from the owners (or better, get also from them a better resolution original).
I am just curious, is this a skybox kind of rendering or a texture mapped on the inner side of a sphere?
Good luck 8)


Yes, exactly, it's a skybox onthe inside of a sphere, so the milkyway texture should be of the same kind as the planet textures (where the poles are stretched out).

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Re: planet texture license? and milkyway texture

Post #4by selden » 18.10.2005, 11:02

aardwolf wrote:I discovered Celestia has very nice textures of all those planets. Are those textures public domain? Can I use them for my spacegame? Are there any restrictions?


Please read GNU Public License v2 as published by the Free Software Foundation at http://www.fsf.org/licensing/licenses/gpl.html. It's what you agreed to when you installed Celestia. It applies to all of Celestia's components.
Selden

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Post #5by Boux » 19.10.2005, 07:41

aardwolf wrote:Yes, exactly, it's a skybox onthe inside of a sphere, so the milkyway texture should be of the same kind as the planet textures (where the poles are stretched out).

When I say "skybox", I am meaning a sky environment implemented in a separate box/mesh of any shape that is seen as a backdrop by the players from the main level (where actual action is happening) through transparent /fake backdrops/ ceiling (or walls and floor).
In Celestia, for example, you can't have a separate "skybox". To achieve the backdrop effect you have to put a huge sphere let say around a star or cluster of stars with a texture mapped on to the inner side. Action is happening /inside/ the sphere, not in a separate "level". This means huge mesh, huge texture(s) and inefficient use of resources.
The separate skybox (by the way it can be any kind of environment and not only sky, such as mountains, caves, inside of a volcano, etc.) is much more flexible and efficient.
This was the meaning of my question. Just curious about the technique you are using.
8)

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Post #6by aardwolf » 19.10.2005, 20:50

Ok, it's a real skybox, meaning that it's not a big sphere put around stars. It's drawn before the rest is drawn and has no coordinates.

More specifically, I draw like this:

First the skybox (milkyway) is draw. Then the stars of other star systems are drawn as dots. Then the planets are sorted and drawn. Everything up to this point is drawn without a zbuffer. And finally when on a planet some more details on the ground are drawn, with zbuffer.

Also if you're on a planet the milkyway and stars will become more translucent or invisible and the sky color is drawn.

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Post #7by Boux » 20.10.2005, 08:05

OK, thanks for the clarification.
What is good with a real skybox is that no actor will ever collide with/reach it.
Would be great to implement switchable skyboxes in Celestia to show up/super-impose in the background different views of the universe.

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Post #8by hank » 20.10.2005, 14:51

Boux wrote:Would be great to implement switchable skyboxes in Celestia to show up/super-impose in the background different views of the universe.

I don't think I understand this. Celestia has no background.

- Hank

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Post #9by Boux » 20.10.2005, 16:25

hank wrote:
Boux wrote:Would be great to implement switchable skyboxes in Celestia to show up/super-impose in the background different views of the universe.
I don't think I understand this. Celestia has no background.

- Hank


Skyboxes could allow for example to draw and display a representation of the fossile microwave background of the universe, or the Hydrogen-alpha or infra-red sky, fancy mythological constellations, anything. The background provided by a skybox is located /beyond/ the virtual world. It is visible but unreachable for the observer/camera.

To have a good idea of how it works, grab a copy of UT 2004 and open a level (a map) preferably with open areas in the 3d editor. The skybox generally sits in a far corner of the virtual world, separated from the map itself. You can visit it in camera mode (free flying).

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Post #10by eburacum45 » 25.10.2005, 18:10

Selden's WMAP add-on makes a nice distant background; if human eyes were sensitive to microwave radiation of this wavelength the sky would look something like this...

http://www.celestiamotherlode.net/catal ... don_id=569

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Post #11by selden » 25.10.2005, 18:20

Well, maybe :)

That particular image is the combination of several different addons as seen from a viewpoint outside(?) the visible universe. Somehow I doubt it would actually look like that from any real viewpoint.

(And I fear that I may have oriented the WMAP image upside down. :( )
Selden

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Post #12by eburacum45 » 25.10.2005, 23:15

Well, I have been experimenting with that WMAP image , making it darker and a little fuzzier, and it looks good as a far distant skybox for stars inside the Milky Way galaxy
(I might make it larger in radius to avoid parallax and flip it if you say it is upsidedown).

I think it resembles the sort of data that might be available to a spacecraft pilot in the distant future when a wide range of wavelengths could be included into his or her sensory input. If a ship is venturing into unknown, perhaps dangerous territory, such input could be very useful.

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Post #13by eburacum45 » 27.10.2005, 16:01

One result I have had is here; this species of far-future human can see the CMB, although the resolution must be poor...
http://www.orionsarm.com/clades/Sailors.html


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