Yet another planet tutorial (Gas Giants)

[sambrookjm]

I have created two methods of making a Gas giant planet. Both of these methods have GIMP scripts that automate the process. The first method, described below, makes a gas giant with fuzzy borders. To start, make an image that is much taller than it is wide. I usually use a 10:1 ratio. For this example, we'll make it 100x1000. The background color doesn't matter much at all, since we'll be rendering lots of plasma.

The next step is to determine how many layers of color you want in your planet. For this example, we'll make four different bands. Make a rectangular selection stretching from the top of the image to one-quarter of the way down. It should go all the way across the image. Using the Position in the Rectangle select dialog box (on the main GIMP tab) will help out considerably. You should have something that looks like the screen below. I've included the Rule of Thirds guidelines in the selection just to make it easier to see.



Now go into the Filters --> Render --> Plasma. Randomize the seed, and select a turbulence level. Two or three is usually a good value.

Once you have rendered the plasma in the selected area, it's time to select another empty area. Doing this manually, the easiest way to accomplish this is to go into Layer --> Transform --> Offset, and offset the layer 250 pixels (1000 layer height divided by four different bands = 250 pixels) in the y-direction. Make sure that your edge behavior is set to Wrap Around. If you are doing this manually, it should look like this:



with an active selection on the top white part of the image.

Repeat this process (Render plasma, offset image) until the entire image is covered with bands of plasma. You can use different turbulence values for each band if you are so inclined.

Once your entire image is filled with plasma, stretch the image so it has a 1:1 aspect ratio. Go into the Image –> Scale Image menu, click on the chain (so you can change the aspect ratio of your image), and set the width equal to the height. It should now look something like this:



Now make the image seamless by going into Filters –> Map --> Make Seamless. Although it's an optional step, it will prevent any jarring discontinuities in the atmosphere of the planet as we continue on.

The next step is to use the Ripple filter to create some sense of vertical turbulence between the layers. Go into Filters –> Distorts --> Ripple. Make sure that “Retain tilablity” is checked, your orientation is Vertical, and your Wave Type is sine.

Period and Amplitude are up to you. I usually use a Period equal to 1/50th of the image size, and an amplitude of 1/300th the image size, rounded down. For our 1000x1000 pixel image, this would be a period of 20 and an amplitude of 3.



If you want to run the Filters → Distorts –> IWarp filter, this would be the time to do so. This will let you create a Great Red Spot on your planet, manually shape the transitions between the bands of plasma, or do pretty much anything you want to. Use your imagination, because it's your planet!

Now we run Filters → Map → Map Objects filter to turn this plane into a sphere. This is why we made the picture seamless a few steps ago. If we hadn't, the borders would show up as discontinuities when certain rotation parameters were used. The values that I change from the default values are shown below:

Options tab:
Map to Sphere
Check the “Transparent background” box
Light tab:
Lightsource type - No Light
Orientation
Z – 0.9 (this makes it take up approximately 90% of the canvas size)

The X, Y and Z rotation values can be modified to get a good view of any features on your planet that you placed there. Mess around with these values a bit, and keep hitting Preview until you like what you see. When you like the picture, run the filter. You should now have something like this:



We're getting there, but it's still not quite right. Use Filters → Blur → Gaussian Blur on the planet to soften up the hard edges a bit. A value of (Image Size)/50 usually works well. Here, that would be a Gaussian blur of 20 pixels.

If you think the colors are too vivid, you can go into the Colors → Hue-Saturation menu, and decrease the saturation of the image by a certain amount. Usually, 30-40 is a good amount. If you like your gas giants to have vivid colors, then by all means skip this step.

That's it! Add in a background and any shadows you want to, and you're all set! I'll post a couple of sample planets in the next post, a PDF version of the tutorial, and a GIMP Script as well.

[sambrookjm]

These pictures are shrunk down considerably from their original size.

A generic gas giant with nothing fancy


A planet with an over exaggerated Great Spot


I've also attached a zip file containing a PDF with the steps of the tutorial, as well as a GIMP script that will do this entire process. Please tell me how to improve this process, since this is my first full-fledged tutorial.

[Sigurd]

Thanks sambrookjim,

Nice targeted succinct tutorial.

Sigurd

[RobA]

Thanks for the tut!

(I think it looks better without the blur, but that is just my own opinion.)

-Rob A>

[sambrookjm]

Thanks for the tut!

(I think it looks better without the blur, but that is just my own opinion.)

Glad to help out with the tutorial. I'm always looking for feedback, especially since this was my first real tutorial.

Maybe I should change the script to make the blur optional? I always felt that the non-blurred version was too sharp for a realistic gas giant, but more options for the user are always a good thing...

[amehatrekkie]

I have a simpler method using Photoshop:

1. have 3 layers: 2 clear ones and the background layer should be solid black or a plain starfield.

2. on the middle layer, create a sphere effect by coloring a small area white and then create 'shadows' around it with progressivly darker gray when u go far from the white area then create a 'terminator' black for the 'night' side

3. then use gaussian blur at around 13 or so so that looks like a gray ball with light shining from behind 'you' to your 'left'

4. on the top layer just create small lines of different colors and alternate light and dark colors then use gaussian blur of around 8 to 13 or so depending if it's a large or 'small' gas giant

5. you can also use this method to create rocky worlds but instead of belts just make it a solid color then draw 'lines' in a darker shade of the same color...and and use gassuian blur of around 5 or so so that it doesn't blur too much

6. you should lower the transparancy of the top layer to about 60% so that the light/shadow of the middle layer shows up and voila, u got a planet in about 20 minutes (if that)...

You should get results like these:

Gas Giant 1:


Gas Giant 2:


Rocky Planet:

[Ascension]

Not at all - we like to see what folks do with our tuts. Nice job.

[someguy]

Well here's what i did.

Still playing with it.

[someguy]

I feel proud of my self.

I made the earth. I had a lot of fun with the fjords. I think it gives the continents a sorta "Baroque" feel.

[su_liam]

Good job. I'm a big fan of fjords, too. Call me Fartislartbag...