Cratered Planets


Today, we’re going to create a cratered world using noise in planetGenesis. This has been a headache for me for some time. The result is far from perfect. I don’t think I’d use it as an elevation map for ground views, but it’s a decent “fractal forgery” from a distance.

First up, we’re going to create the basic heightfield in planetGenesis. Right-click, Add Noise>Worley>Summed Worley Modified by Perlin. Select the new node and set Neighbor to 7, Points per Cell to 4 and Height, Width and Depth to about 1. So far, not so good. Next, we want to add a warping noise to reduce the very ordered shape of this noise. Add Noise>Perlin>Perlin’s Noise. Leave the settings on this one largely alone except to alter the Length, Width and Height under Noise Size to about 1. Now, Add Function>Adjustments setting Scale to about 0.2. Shift drag a link from the output of the Perlin node to the input on top of the Adjust node. Now Add Combiner>Warp and connect the output of the Worley noise node to the right input on the Warp node and connect the Adjust node to the left input of the Warp node. To the output at the bottom of the Warp node connect a Musgrave HeteroFractallize node. The effect here is starting to look interesting.

As much as I like the look so far, I would like to add an effect similar to lunar maria. Add a new Perlin Noise node with Noise Size values of 1,1,1. Add Function>Range, I set the Lower End to -0.1, the Ramp to 1.0 and the Value above range to 1.0. Connect the output of the last Perlin node to the input of the Range node. Feed the outputs of the HeteroFractal node and the range node to a new Multiply node. Feed the output of the Multiply node to the  Terrain node and Run. Try opening the result in Wilbur, also add the same image as a texture in Lighting Settings. Let’s keep this as our texture.

In the Terrain node, change the image file name. Attach the output from the Range node to a new Adjust node, set the Scale on that to about 9. Attach the output of the new Adjust node to a new Add node. To the other input of the Add combiner, connect the output of the Multiply node. Finally connect the output of the Add node to the Terrain node. This is basically to force the highlands to a higher elevation than the maria.

Our cratered planet with hillshade rendered in Wilbur.

Our cratered planet with hillshade rendered in Wilbur.

Now, in Wilbur, we look at the bumpmap we have just created with the previously created image as a texture. For what it is, the effect is pretty decent. For something I came across more or less accidentally and am still trying to refine, it’s pretty awesome. I think it may be possible to enhance the craters a little bit in Photoshop.

There’s a lot of controls in there with no obvious sense of what their results might be. I still recommend blind messing about over slavishly following instructions. That’s mostly how I found this… The Scale values in the Adjustment nodes and pretty much everything in the Range nodes are very sensitive to the values produced by the noise, so that may need rejiggering when the seeds are changed.

For the sake of illustration and to get you started, I’ve saved zipped up pG nodefiles for creating the bumpmap and texture images. Mess around with them, change the seeds to create different planets. Let me know if you come up with anything cool or use this for anything interesting.

Now, let’s look at this “in space.” I’ll start by launching Blender, and deleting the default cube. Next, I’ll create a UV Sphere of Size 3.000. Make sure all faces are Shade Smooth. With the sphere selected, I’ll add a new Material and a new Texture of Type Image or Movie. Load the bumpmap image. Turn Off the Color Influence and turn on the Normal Influence under Geometry.

Now, add another new image texture and load the texture image. Keep the Color Influence. Now render.

For now, I’ll leave it as an exercise for the reader to figure out how to extract the z-buffer to Photoshop and use it to composite the image with a Flaming Pear Glitterato background.

Hopefully this will be useful.

Thank you for your attention,

The Astrographer

EDIT: I forgot to post the planetGenesis nodefiles, so I’m posting them now along with heightfield and texture images rendered to 8k x 4k resolution, a nice composite image created in Blender and a blenderfile showing both how the cratered planet material goes together, and, if you check the nodes view, how the compositing was done. Here it is. Thank you for your patience…

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