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Sample results (second one is what I got making this tutorial):
Step 1 - New Image
Ok, first things first. Planets are big. Really big. The canvas you'll be working on should also be really big, but not because planets are big. The reason is becuase this tutorial will make use of Map Object filter, which tends to give blurry/bad results if you don't scale the image down afterwards. As a general rule, make your image about twice the size you want the final result to be. It should also always be square. The canvas size I will be using is 3000x3000 pixels. If you don't think your computer can handle this, feel free to use a smaller size. Just note that you will need to adjust the blur levels/other settings because you have a smaller image. These are the settings for my image:
You may get a message informing you that the image is larger than the Maximum Image Size defined in your preferences. Just click OK and it will create the image anyway.
Fill the background layer with black.
At this point, you should have a completely black image (obviously), so I don't think I need to show you what you should have by now.
Step 2 - Planet Surface
Create a new transparent layer and call it "surface." With this layer selected, go to Filters -> Render -> Clouds -> Plasma.
Don't be surprised if this takes longer than you're used to. You're (probably) working on 3000x3000 pixels, which means 9,000,000 pixels of plasma to render. It's actually a wonder GIMP does it so fast.
Now, Layer -> Colors -> Desaturate, followed by Layer -> Colors -> Colorize.
If this is your first time through the tutorial, I do recommend you use my values (or something close). This will make later steps easier to follow.
The last thing to do for now is to run Filters -> Map -> Make Seamless. This is optional, but it makes your planet surface a bit more uniform in terms of lightness, which I find gives better results. Roughly what you should have right now:
Step 3 - Clouds
Again, create a new transparent layer, but this time name it "clouds." Filters -> Render -> Clouds -> Plasma again.
Layer -> Colors -> Desaturate again.
We will run colorize on the clouds layer later in the tutorial, but for now leave it black and white. This next part is one of the more time-consuming steps. Go to Filters -> Distorts -> IWarp. You should get a window similar to this:
What you're going to do is use the Swirl CCW (counter-clockwise) and Swirl CW (clockwise) to make these a little more turbulent. Make sure you get every part of the image, and try not to swirl too much in any one spot. If you mess up, you can use the remove option. It's ok to leave the deform radius and deform amount at the values shown in my image; that's what I did. By the end you should have something like this:
WAIT! Don't click the OK button just yet. Think for a moment. If you have a slow computer and are using a large canvas size, you may just want to say "Oh, so that's how it's done" and click Cancel. I have a fast computer, but even for me this step takes a long while. If you choose to click OK (I suggest you do if you have the time) be prepared to wait a while. Get something to drink, walk the dog, or read ahead in the tutorial if you need something to occupy you (besides watching GIMP's progress bar).
Once IWarp completes, run Filters -> Map -> Make Seamless just like you did on the surface layer.
By this point you should have something like this:
Step 4 - Bump Map
This step is optional. If you don't care so much, feel free to skip it. I must stronly suggest you do this, however, since I find it's well worth your time.
Create two new layers called "bumpmap 1" and "bumpmap 2." Make sure bumpmap 2 is above bumpmap 1. Select the bumpmap 1 layer and do Filters -> Render -> Clouds -> Solid Noise. Why not plasma? You'll see in a moment.
Now select bumpmap 2 and do Ctrl+F to run the same filter again. If you remembered to check "Randomize," you will get different noise than you did the first time. Change the layer mode on bumpmap 2 to difference, right-click on it in the layers dialogue and choose "Merge Down." Now go to Layer -> Colors -> Invert.
Look at the result you get. We're going to use this as a bumpmap for the surface later. Notice how you have white lines curving all over? Those will be mountains. :w:
You should have something like this right now:
Move the bumpmap 1 layer to just above the background layer so you can see the clouds again.
Step 5 - A Little More Round
Ok, now it's time to make this look a little more like a planet and less flat. If you want, duplicate all your layers as backups. Change the word "copy" in each one to "backup" so you have "surface backup," "clouds backup," and maybe "bumpmap 1 backup." That's optional, but if you make a mistake later it's easier to fix. With an image this size, GIMP's Undo doesn't go very far back. Be sure to remove visibility on the backups by clicking the eye next to each one in the layers dialogue.
Select your clouds layer and run Filters -> Map -> Map Object. These are my settings. Use them all the way they appear, but feel free to experiment with the Rotation section of the Orientation tab. Your clouds probably came out different than mine and may look better at a different angle.
This is another time-consuming filter if you have a big canvas, but trust me, it's still shorter than the IWarp.
At this point you may be wondering why I set the lightsource to "no light." The reason is because you gain much more control (and generally better results) by doing the light yourself. It may also be faster to do it yourself, since the filter takes much longer when it needs to add light. :w: You may also be wondering why do Map Object at all if you don't want the lighting. The reason is because it will distort the object to look like a sphere and not a piece of paper. The distortion, however, is the reason why you need a large canvas: things near the "equator" of the planet will be stretched and generally won't look as good at 100% size.
Now select the surface layer and do Ctrl+F to run Map Object in the exact same way.
If you skipped the bumpmap step, you can now move on to Step 6. Otherwise, select your bumpmap 1 layer and do Shift+Ctrl+F to show Map Object with the same settings. In the Orientation tab, change the Z value under Position to .91 instead of .90 to make the sphere a little larger. If you don't do this, your surface layer will get some nasty artifacts around the edges.
The reason we're mapping the bumpmap layer and the surface layer instead of doing the bump mapping beforehand is to avoid unnatural lighting. If your sphere gets oriented so that the shadows point toward the light source instead of away, that's not good.
By this point your image should look something like this (those of you without the bumpmap layer won't have the lighter ring around it):
Step 6 - A Little More Spherical
So, your layers are all round now. That's good, but the tricky bit is still to come. This may be difficult to follow, but I'll try my best.
First, the shadow. You want to get an elliptical selection which you will fill with black to make the shadow. How you should drag your mouse is shown (roughly) below.
Create a new layer called "shadow" and fill the selection with black. Deselect and run Filters -> Blur -> Gaussian Blur.
NOTE: If you're using a different size canvas, you will need to use a different blur amount.
Looking better already. :h: Before continuing, remove visibility on the bumpmap 1 layer by clicking the eye next to it in the layers dialogue.
Now do exactly what you did to get the selection for the shadow layer, but start at the bottom right corner of the image and drag holding down only Shift (NOT Ctrl) so that you leave only a sliver of the planet outside your selection. Make a new layer called "highlight."
Select -> Invert, then fill the selection with white, then Select -> None.
Filters -> Blur -> Gaussian Blur with IIR and 50x50. (Again, smaller canvas users must adjust this amount.)
Right click on the surface layer and go to Alpha to Selection.
Select -> Invert. Select the highlight layer and do Edit -> Clear.
You should have something like this:
Make a new layer called "diffuse." Repeat what you did for the highlight layer exactly, except this time select so that the border of the selection lies about halfway between the edge of the shadow and the edge of the highlight. Also, instead of blurring 50x50, blur by just over half what you did for the shadow. I used 300x300. You should now have this:
Now move the diffuse layer below the highlight layer. A thin black line may appear on the edge of the highlight. If so, run Filters -> Colors -> Color to Alpha. Click on the color shown in the dialogue box, and choose complete black instead. The line should disappear.
If you've somehow managed to follow all that, here's what you should have:
Step 7 - Bring It All Together
Here's what you should set your layer modes to:
highlight: Soft Light
diffuse: Soft Light
shadow: Normal
clouds: Hard Light
surface: Normal
That makes everything about 100% better. Observe:
If you have a bumpmap layer, now is the time to use it. Select the surface layer and do Filters -> Map -> Bump Map.
Do Ctrl+F and run it again just for good measure.
Remember I told you we'd colorize the clouds layer eventually? Now's the time. Run Layer -> Colors -> Colorize and choose a hue roughly opposite what your surface layer is. Here are my settings:
Due to the nature of the Hard Light layer mode, this adds some more color variation to the planet surface. Granted, these aren't really clouds anymore, but so sue me. :w:
Step 8 - Final Touches
The first thing I notice is that the diffuse and highlight aren't really all that bright. Duplicate the diffuse layer until it's bright enough and the highlight layer as well. In my case, I wound up with two of each (though in the example at top, I have 3 diffuse layers and 4 highlights).
The last thing you may realize is that, if you were to place this in some kind of scene elsewhere, the shadow layer would interfere with the background. (Draw in white on your background layer if you don't believe me.) To fix this, right click on the surface layer and choose Alpha to Selection. Select -> Invert, then choose the shadow layer. Run Edit -> Clear then deselect and it's fixed.
Final result:
Well, that's that! I hope you managed to follow the entire thing, and I also hope your internet connection didn't catch fire. As a few final notes, when scaling down, it's actually a good idea to use "None (fastest)" as the interpolation type, since it's quicker and sometimes gives better results. Compare the final result to the example at top. The example was scaled using None, the final result was (accidentally) scaled using Linear. Also, this tutorial doesn't cover making a background for this thing (obviously). For now, it's up to you to find a way (or a tutorial).
So farewell, and happy GIMP-ing! :h:
go there. GFXunited.com. Where PS and Gimp users live in peace.
