Introduction
This tutorial is part of a series about creating textures that can be used as surfaces for planets. They can be converted into 2D planets using this 2D Planet Sprites tutorial or used as materials for texturing 3D spheres. This tutorial shows how to create the planet surface textures, while the Planet Sprites tutorial demonstrates how to use these textures to make 2D planets.
Textures for Gas Giants, much like textures for Terrestrial or Rocky Planets, are composed of multiple blended layers of noise and filters. The main difference is that everything is predominantly horizontal. This comes down to the type of Noise used to create the appearance of banded gases swirling around the planet. The process itself may seem a bit simpler, since you don’t have to use as many brushes or do as much manual editing as you would for a terrestrial or rocky planet, but the techniques are very similar.
Example Gas Giant Texture
As usual, the techniques covered in this tutorial are possible using just about any image editing software, but the names or features may differ depending on which one you choose. For the sake of this tutorial, I will be using our favorite free software, GIMP for most of the example images unless otherwise specified.
Hand Painted Textures
The quick and dirty method for creating Gas Giant textures is to do it by hand. It even sounds more complicated than it actually is, and you’ll find it is incredibly simple once you’ve done it a few times!
To start with, create a blank image at whichever size you need for your planet surface. For this tutorial, I will be using a 512×512 canvas rather than a 2:1 texture. Begin by selecting colors and using the Brush tool to fill your canvas with a number of horizontal lines. It helps to cycle between lighter and darker colors to create the different colored bands of gas.
Lines Drawn with the Brush Tool
Once you are happy with your lines, we need to blur the image, so the lines don’t look so horrible. Select Filters -> Blur -> Gaussian Blur from the menu to bring up the settings for the Gaussian Blur filter. Drag the X and Y sliders toward the right until you are satisfied with the amount of blurring. I have gone ahead and used a value of about 16.
Blurred Lines
Now create a new layer above the first one. We are going to do pretty much the same thing here, only this time we will leave some empty spaces so that the bottom layer can still be seen in some places. It helps to use a brush with soft edges so the colors can blend easier, but you can use whichever brush you like.
Additional Layer of Lines
Once again, we need to apply a Gaussian Blur to this layer as well. Simply repeat the previous steps to blur the top layer of lines. The next step is a matter of preference or experimentation, as each Blend Mode offers different variations or appearances. Change the Blend Mode to something more interesting so the two layers blend together. For this tutorial, I have selected the Addition blend mode.
Addition Blend Mode
It doesn’t quite look like a gas giant yet, but that’s because there are no storms! All we have so far are wispy bands of colored gas, and that’s not very interesting. Select the Warp tool or press the W key on the keyboard to make the Warp tool active. Starting with the top layer, use the cursor to make small circular motions around the edges of the colored bands.
Swirled Storm Clouds
Continue doing this swirling warp motion with the bottom layer to create another layer of swirls beneath the upper atmosphere. I am going to stop here with these two layers for now, but feel free to continue adding more layers of color and warp swirls to add more detail to your texture. That is where these techniques shine the most, especially when working on planet terrain or even space backgrounds. The more layers of detail the better!
Now we cannot simply apply GIMP‘s standard Seamless filter to this texture, since we do not need the top and bottom edges of the texture to line up. We only need the left and right edges to tile with each other. From the menu at the top of the screen, select Layer -> Transform -> Offset to bring up the Offset options.
Shift by 1/2 Width
The texture needs to be offset by 1/2 its width, so click on the By Width/2 button. This will shift the entire texture over by 50% while simultaneously wrapping around from the other side of the image. Now it is very easy to see the clear seam running down the center of the texture.
Texture Offset by 50%
The easiest way to fix this seam is to use either the Clone Stamp tool or the Healing Brush. My personal preference is the Healing Brush, but feel free to use whichever you are more comfortable with to remove the seam. From here, you can offset the image back to its original position, or you can simply save and export your texture as it is with the fixed seam in the center.
Final Manually Painted Gas Giant
You can use any of the methods outlined in the 2D Planet Sprites tutorial to convert your planet texture into static 2D images or even rotating animated spheres using GIMP, or you can import your texture into any 3D software for mapping to spheres. The key to adding detail is to continuously add more layers to your image with different elements you can blend into the previous layers. Just try experimenting a bit!
Noise Based Textures
Another great way to make textures for Gas Giants is to utilize Noise generation, a feature that comes with most image editing software. While you could manually paint every planet texture you need following the first section of the tutorial, you can save a lot of time and even get better looking results by using the Noise filters that come with your image editing software. Many of the steps are quite similar to those outlined already, with a few small differences.
To start with, create a blank image at whichever size you need for your planet surface. For this tutorial, I will be using a 512×512 canvas rather than a 2:1 texture. Gas giants are made up of different colored bands of gases, so we want to use a Noise generator to help us create the light and dark areas of our texture. Click on Filter -> Render -> Noise -> Solid Noise to bring up the Solid Noise filter options. If you are using Photoshop, you will want to use Render -> Fibers for this step instead.
Solid Noise Filter Settings
Set the X slider to 0.10, the Y slider to 16.0, and the Detail slider to 15.0 to create a streaky, banded texture. You can experiment with the X and Y sliders to your liking. Be sure to select the Tileable option to not only ensure the texture is seamless along the edges, but also to add a little bit more waviness and variation to the banding. You can also change the Random Seed value or press the New Seed button to get a different variation of noise. Press OK to confirm the settings and you should have something that looks similar to the example image below.
Bands of Varying Brightness
The next step is not necessarily required, but it does help add another layer of detail to the texture. Create a new blank layer and repeat the process from above using the same settings to generate another Solid Noise, only this time select a different Random Seed value, so the bands are different for the new layer. Now in order for the top layer to have any effect on the bottom layer, we need to change the Blend Mode by using the drop-down menu above the layers. I am going to use Overlay for this tutorial, but feel free to select any blending mode that looks good to you.
Blended Layers of Solid Noise
Now that we have the basis for our gas clouds, right click on the top layer and select Merge Down to combine the two layers. Now we need to make them look a little bit more like storm clouds on a gas giant. Much like we did in the first section of the tutorial, we can use the Warp tool. Simply press the W key to activate the Warp tool. You can change the settings of the brush using the panel to the left of the canvas.
Warped Storm Clouds
Use circular or up and down motions to create swirls and waves throughout the image. You may have to go over it several times to make it look more and more like swirling storm clouds. Now we could stop here, but there is another useful Filter we can take advantage of to give the texture a little bit more waviness. Select Filter -> Distort -> Ripple to bring up the options window. This filter will create a wavy distortion across the entire image, but there are a few settings to tweak first.
Ripple Filter Settings
For the first pass, set the Amplitude slider to 2.0, the Period slider to 150, and change the Abyss Policy setting to Loop. The Abyss Policy setting determines how the filter deals with areas of the image that go beyond the canvas or reveal transparency below them. By changing it to Loop, it ensures the texture wraps around the top and bottom edges so there are no seams.
Rippled Storm Clouds
We can do this one more time using slightly different settings in order to apply another layer of ripples to the texture. This time, change the Amplitude slider to 1.0, the Period slider to 60, and the Phase Shift slider to 0.5 to introduce a layer of smaller ripples to the texture.
Smaller Ripples
Now you can go back through and add more swirls and warping if you prefer. In order to add some color to our clouds, we need to create another new layer. For this layer, we are going to use the Gradient tool to create a multicolor gradient. Click and hold the Paint Bucket tool to bring up a drop-down menu where you can select the Gradient tool.
Gradient Settings
Using the settings panel on the left of the canvas, make sure the gradient Shape is set to Linear and choose a gradient color palette from the list of options. I have selected the palette called Browns since it already resembles the color of a gas giant. Once you have made sure the settings are correct, click somewhere near the top of the canvas, and while holding Ctrl, drag the cursor down to the bottom of the canvas and press Enter to confirm the gradient. It should look something similar to the example image below.
Brown Striped Gradient
Once again, we won’t be able to see any changes until we select a different Blend Mode from the list of options. I’ve gone ahead and selected Addition for this tutorial, but feel free to try out the different blend modes to get different types of results. This is also a useful way to make different variations of gas clouds, as the different modes sometimes alter the colors of the image as well.
Gradient Layer set to Addition
Using lower Y values when generating your Solid Noise layers will result in there being less gas bands. You can also repeat the first several steps multiple times, including manually warping each individual layer with storm swirls, to create more complex looking storm bands. Right click on the Gradient layer and select Merge Down to merge the layers together. All there is left is to save and export your finished Gas Planet texture. Be sure to do this before doing any additional work on the texture, just in case!
Final 2D Planet
Try to combine techniques from both sections of the tutorial to produce even more detailed custom Gas Giant textures. You can also use any of the methods outlined in the 2D Planet Sprites tutorial to convert your planet texture into static 2D images or even rotating animated spheres using GIMP, or you can import your texture into any 3D software for mapping to spheres. Textures for Gas Giants should be fine as they are for texture work, but you might want to take a peek at this Spherical Textures tutorial if you plan on working with 3D spheres!
*This tutorial will be expanded over time!