Author Topic: Celestial Objects Thread  (Read 174455 times)

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Offline Herra Tohtori

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Celestial Objects Thread
Well, I came across an excellent GIMP tutorial on how to make planets, so naturally I wanted to try myself what I could accomplish. The results I got with following the guide didn't actually satisfy me, so I came up with a little modified technique. I got some pretty rocks made... I wanted to try and make Earth-like planets at first, because they are IMO the most complex to make.

Then I came here looking for a nice thread featuring planets and stuff, but I didn't really find one! All were like year or two old and had mostly dead links and some people who I've never before seen here, so I decided it was time to make a new topic for planetary art that HLP user pool spews at random intervals. I'll start with two of my planets I made yesterday and today.

So, first planet looked like this:



Don't let the number 2 in file name to distract you, that's because there was already an older planeetta_1 file in the dir.

Well of course I wanted to try and make it even better. This time I spent more time with the surface map, putting in mountains and ice caps (which were after all mostly non-visible), and more defined seas and continents. I also spent some time to create a more complex array of clouds, and behold, this was the result of 2nd attempt:



The shadow layer seems to be a bit off for some reason... I'll have to give it a fix. Both of these planets can also be shown without the shadow, or they can be fitted with any kind of a shadow layer I can think of. Though that would also mean that the diffuse atmospheric glows should be re-made...


So, what do you think? Also, feel free to post your own planetary creations and stuff. After all, I personally think there's a little too few planets around in Freespace...
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline Lt.Cannonfodder

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Re: Celestial Objects Thread
Not bad, Herra Lekuri. Your planets have a  really artistic feel to them.

As it happens... I just finished this piece:



Then a planet that is almost a year old and thus ancient history on my scale, but still one of my long time favorites.


 

Offline Herra Tohtori

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Re: Celestial Objects Thread
Beautiful... :nod:

Remarkable how different planets come out from different people, eh?

Did you use actual Earth world map in that High Orbit picture? I'm having some difficulty finding a high-res picture of earth. Of course, I could use whatever kind of surface map.

Actually I found out today that GIMP is a very wise thing for free program (even more so than I thought previously).

You can import any planet's surface map in high-res, resize it onto a square, make it seamless (not even necessary) and then do map to object (ball)... And it creates a planet that has correct continents and stuff, like you planned it onto the level map. Cool thing.

Another question - did you use bump mapping to the cloud layer? I did, and it ended up much better looking than without. After all, clouds are higher than ground (usually). :D Oh, and would you want to reveal how you make that nice blue atmospheric diffuse light that strengthens in the distance? It looks so real that I almost fear my screen will break and the air in my room be gushed into vacuum... well, not really, but almost. :cool:
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline watsisname

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Re: Celestial Objects Thread
Wow, those are really beautiful!  I'll give this a try tonight when I've got more spare time and see what I can do with this.

Looking through that tutorial, I noticed that the method of making the planetary shadow is a bit flawed.  If you look carefully at a real planet shadow, you'll notice that it's not the same as a dark circle superimposed over the planet's disk.  That said, it's still very cool and I'm just letting my perfectionistic astronomy nerd of an ego complain at it.  ;)
In my world of sleepers, everything will be erased.
I'll be your religion, your only endless ideal.
Slowly we crawl in the dark.
Swallowed by the seductive night.

 

Offline Herra Tohtori

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Re: Celestial Objects Thread
Well...

There's nothing wrong in itself if you put a circular shaped terminator onto a planet.

The only thing is that the border of light and dark must divide the ball into half. That means that the only really important points are the points where the shadow starts on the edge of the planet's visible half. The line drawn between these two points must divide the visible half of the planet into half, if there is a shadow visible. So, you could use the rectangular selection as long as the direct line draws the planet into half...

I don't know if I got this explained as understandably as I wanted, but if you don't get it the reason is not in you, but in my Enklish tongue. :D I'll post a picture of how a spherical object creates a shadow, if you don't understand my gibberish.
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Offline watsisname

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Re: Celestial Objects Thread
Yes, I more or less understand that.  :)

Hmm, I gave that a bit more thought.  It turns out it DOES work out correctly (using a circle to make the shadow), but the radius of the circle will vary depending on what the percentage of the planet's disk (relative to the observer) is in shadow.  The more of the planet is in shadow, the smaller the radius of the circle. 
Also, if the illuminating object (sun) appears as a point in the sky, then the two points where the terminator line meets the edge of the planet disk will be directly opposite each other, and the terminator line will be crisp. (I think that's what you were referring to in your post) Conversely, the larger the apparent size of the star, the more "blurred" the shadow line is, and the shadow/planet-disk intersection points will be close together (further toward the dark-side of the planet).

...I hope that made sense.  :lol:

Oh, some pictures of the lunar phases to go with what I'm saying.  Notice that you *can* use a portion of a circle's arc to describe the terminator line, and the radius of that circle increases as the area of the moon that is covered in shadow increases.
http://aa.usno.navy.mil/graphics/Moon_phases.jpg
In my world of sleepers, everything will be erased.
I'll be your religion, your only endless ideal.
Slowly we crawl in the dark.
Swallowed by the seductive night.

 

Offline Herra Tohtori

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Re: Celestial Objects Thread
The sharpness of the terminator is more linked to atmospheric qualities of the planet than the apparent diameter of local light source.

Of course apparent diameter also affects, but atmosphere has even bigger effect. Take a look at moon and you see much sharper terminator than on pictures of earth. Conversely, if you go to Jupiter distance and look at Jupiter (whopping big and dense atmosphere) and some of the barren rocks they call moons (say, Callisto or Ganymede) and the shadow is much sharper again.

Though there aren't completely sharp shadows anywhere in solar system due to the nature of the surfaces of planets/moons.


Oh, I decided to experiment with the "Render to Object" function a bit... I used THIS as the starting point, and ended up with this...




 :D

Aside from some polar squeezation I say that GIMP is a very useful tool. I mean, look at it. It looks like a planet to me...

Hell, I could scan some old maps from various fantasy book series' and put them into planets, and if someone recognized them I could well give them cookie or two... :lol:
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline Pyro MX

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Re: Celestial Objects Thread
Woohoo another GIMPer! I am not alone!

That said, nice planets. And nice tutorials too. I never used that "map to object" thingy and I was doing all the "sphere" look with lens effects. Well, it's sure nice to learn new thechniques like that. GIMP rocks.

Keep up the good work!

 

Offline Lt.Cannonfodder

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Re: Celestial Objects Thread
Remarkable how different planets come out from different people, eh?
I actually use Lightwave to render the planets, so ours are not directly comparable. I've done some PS planets though, and my general feeling is that using pure 2d results in more "artistic" looking planets. If you want realism, 3d is the easiest way.

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Did you use actual Earth world map in that High Orbit picture? I'm having some difficulty finding a high-res picture of earth. Of course, I could use whatever kind of surface map.
8k color, 8k spec, 8k bump and 16k clouds, plus some additions procedural textures on the clouds and spec layer. I would have used 16k for all, but LW crashes when I try that :)

All maps taken from http://www.celestiamotherlode.net/

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Oh, and would you want to reveal how you make that nice blue atmospheric diffuse light that strengthens in the distance? It looks so real that I almost fear my screen will break and the air in my room be gushed into vacuum... well, not really, but almost. :cool:
As it's done in LW, I can't help you much with GIMP.

You have no idea how long I tweaked that atmosphere to get it about right. And the colors look all wrong if I zoom out with the camera and look at the sphere from a distance.

 

Offline Lt.Cannonfodder

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Re: Celestial Objects Thread
Rusty!


 

Offline Colonol Dekker

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Re: Celestial Objects Thread
I dotn wanna type Gimp into google at work, so can someone provide a link please :)

 

Offline Herra Tohtori

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Re: Celestial Objects Thread
The GIMP. :nod:

If you are used to more of a classic interface, get GIMPShop. That you can find from HERE or HERE. It basically makes the main GIMP window more of a traditional image editing program's main window.

I like using the normal GIMP, though.
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline watsisname

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Re: Celestial Objects Thread
Well, I've gone through the "make a better planet" guide, and here's what I've come up with.  It's a tad bit screwy at lower "pole", but I'll totally be getting better at this and not let that happen again.


GIMP is teh sweetness. :D
In my world of sleepers, everything will be erased.
I'll be your religion, your only endless ideal.
Slowly we crawl in the dark.
Swallowed by the seductive night.

 

Offline Dark Hunter

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Re: Celestial Objects Thread
Can we release the .pcx images for these planets? They sure beat most (if not all) of the planets currently available...


On the other hand.... FS only allows 16-color background PCX's, which sucks.... that might become a problem.
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Offline Herra Tohtori

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Re: Celestial Objects Thread
Skyboxes with textures are the solution to that problem...

AFAIK they use similar (almost) textures than the models and effects, and textures can be practically as good as you can make them, for example 32-bit DDS (or are they actually 24-bit...?) or TGA pictures.

Anyway, skyboxes are quite a lot better in most regards as backgrounds than traditional background images, as far as I know. I'll have to check the wiki if there's a skybox howto/description...
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline Lt.Cannonfodder

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Re: Celestial Objects Thread
AFAIK they use similar (almost) textures than the models and effects, and textures can be practically as good as you can make them, for example 32-bit DDS (or are they actually 24-bit...?) or TGA pictures.
Never ever use 256-color pcx images as backgrounds again. Use 24bit dds for nebulas, 32bit dds for planets. You need the alpha channel in planets or you'll get an ugly black box. 1024x1024 is good resolution most of the time.

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Anyway, skyboxes are quite a lot better in most regards as backgrounds than traditional background images, as far as I know. I'll have to check the wiki if there's a skybox howto/description...
Normal backgrounds are still very good if done right. Skyboxes are good for special cases, like a mission taking place very near a planet. Here's how I did the big gas giant skybox for the BtRL:



The outer sphere is inverted and mapped cubically with a 2048x2048 starfield texture. The planet is just a flat plane, texture is also 2048x2048.

 

Offline Herra Tohtori

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Re: Celestial Objects Thread
Well, now I know more. Thanks. :D

By the way, I created an image of MArs for comparision purposese between LW and GIMP in planet making. Not to define which one is better or worse, but just to find out differences and perhaps use that knowledge in GIMP to make the result even closer to realism factor achieved by 3D software.

Here it is:



It's the God of War on his more stormy season, apparently.

Oh and by the way, I figured out a theoretically perfect way to generate correctly shaped shadows. It goes like this:

-create a new white layer
-slice the layer in half vertically
-flood the other half with black and leave the other half white

-select Map to Object; rotate the half-white, half-black ball until you find a good shadow shape

-make white part of the picture transparent

-blur the edge of shadow crossing the planet's sphere. There. I used this method with that Mars pic there.

...oh, and very many thanks to Lt.Cannonfodder for reminding me of Celestiamotherlode. Excellent content there, if you want to create planets of the solar system.  :nod:
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline watsisname

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Re: Celestial Objects Thread
Would anyone mind sharing some techniques for making good atmospheres?  I've tried bounding the planet with a mostly transparent white layer with gaussian blur, and placing that layer below the shadow layer, but I'm sure there's a better way of doing it.
In my world of sleepers, everything will be erased.
I'll be your religion, your only endless ideal.
Slowly we crawl in the dark.
Swallowed by the seductive night.

 

Offline Herra Tohtori

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Re: Celestial Objects Thread
Surrounding the planet with white blur kinda works, but the rouble is that it also reaches to the shadow side, which is sort of unrealistic.

Here's what I do... When I get everything else sorted out onto it's place - surface, clouds, shadow - I choose "Copy Visible" or whatever it is in English version of GIMP. That copies what is currently visible - a sharp-edged planet, that is - onto clipboard.

Then I create a new layer behind th esurface layer and paste the clipboard information there. Then I Gaussian Blur this layer on about 50-100 strength, depending on thickness and density of the atmosphere. There is the surrounding atmosphere you're looking for.

It does not hinder the visible part of the planet, because it's behind the surface layer. However, it reaches some distance away from the edge, making a low opaque atmosphere which is roughly the same colour as the planet.

If I want to get some atmospheric effect onto the surface also and not just edges, I duplicate this same layer, move it just behind the shadow layer - meaning that it is over the cloud level - and set the layer mode to Soft Light. That does an interesting effect, for example in that Mars picture it made the clouds more dusty yellow. Tryi with this kind of things yourself... I've noticed that it's very very hard to set up a good-looking uniform colour blurred atmosphere. Though I would suggest trying making a circular gradient field that is most transparent at the middle and gets thicker going towards the edges... Choose a colour that fits the composition of planet's atmosphere. Then blur this layer and place it on top of cloud layer, and adjust the colours and opacity of the layer until you get good results.

Earth atmosphere is sky blue, Mars atmosphere is probably bluish grey in reality... though it's so sparse that it hardly has much colour into it. Titan should have thick, orange-ish atmosphere. Try different styles, but I use the technique I mentioned first, it's fast, simple and gives satisfactory results.
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline watsisname

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Re: Celestial Objects Thread
Ok, thanks very much for that info.  That totally sounds better than what I was doing.  :o
And expect some more pictures from me whenever I get more time to play with this.

Edit:  Um, wait a moment.  The method I was using doesn't have atmosphere effect on the darkside, since it's covered by the shadow layer.  Observe:

Er, well in this case it's slightly noticible since my shadow layer isn't at 100% opacity.  I usually like to have a tiny amount of "abient light" on my planets.
And yeah, I got starfield-making down pretty good now, too.

Edit2:  And here's my latest bit of work.  Needs some touchups with the nebulae, perhaps, but I quite like it. :)
« Last Edit: September 04, 2006, 03:47:09 pm by watsisname »
In my world of sleepers, everything will be erased.
I'll be your religion, your only endless ideal.
Slowly we crawl in the dark.
Swallowed by the seductive night.