Generate Planetary Terrain

[Hugh_Bowen]

I want enough heightmaps for a planets. Any suggestions?

[blattacker]

Strictly speaking, any heightmap can be used for an entire planet, it just depends on the level of detail you’re looking for. If you’re simply looking to have terrain features visible on a moon from the surface of a different planet, for example, you could very likely get away with doing just a basic heightmap at the highest resolution your computer can build quickly, and stretching that over the visible surface of the moon.

If, however, you are looking for a fine-detail heightmap for an entire planet, there’s some serious considerations you’ll need to make. First and foremost is the fact that World Machine is not exactly designed for (realistic/geologically accurate) planetary level terrains. While it can certainly be used for such things (I’ve done this myself in making fantasy maps), it is definitely not its strongest suit. Moving past that, if this is for a game, you’ll likely want to make the world in parts. There are a few tutorials out there on the Internet for making general terrains and then honing in on different regions, then stitching all that together. It’s not something I’ve personally tried, so I can’t speak to the ease, but it’s definitely possible. I believe there are some GeekAtPlay tutorials that cover this in depth, though they use a much older version of World Machine. Keep in mind that, for most games, you should be able to get away with not having the entire surface of the planet traversable, and thus don’t have to have a single complete heightmap and can instead build only the traversable parts, and have the heightmaps for different traversable regions completely separate. That being said, if you’re planning on creating planets for a game similar to No Man’s Sky where the entire surface of a planet is theoretically traversable, it will be best to keep the terrain itself rather simple. Using No Man’s Sky as an example, I don’t think I’ve ever seen flow lines on a single planet. I don’t think I’ve ever seen any features that imply erosion, in fact. My guess is that each planet is given a form of perlin noise with a unique seed, and some just have a global sea level applied. This, to me, is evidenced especially by the fact that every planet seems to be a single biome planet, and you can very much take cues from that approach.

If you’re more looking at rendering the terrain for applications such as film/television or digital art (this is mostly what I do, so this is the aspect I’m most familiar with), you once again run into the benefits of only building what you see. If you’re looking at a planet from space, for example, you only need, at most, slightly more than half of the surface to have displacement (unless there’s some weird physics going on with a nearby black hole, in which case, godspeed), and, once again, it doesn’t need to be incredibly high quality. Never underestimate the power of using color textures to imply more information than is actually present. If you’re on the surface of a planet, or in the atmosphere, you only need to build out what’s visible to the horizon, and only the nearest displacement needs to be a higher quality, anything receding into the distance can be built out at progressively lower resolutions to save on build time and filesize.

Lastly, if you’re looking at 2D applications, such as making maps for books/ttrpgs/fun, your best bet, once again, is to either build the entire planet at once at a lower resolution (possibly either using the aforementioned color textures to imply more detail than actually exists, or manually adding detail in post), or to build a single continent at a time (or even a section of a continent at a time) and stitch them together. My preferred method is to build a single continent at a slightly higher resolution, and put everything together in Photoshop. If you want elevation detail for the ocean floor as well (for example, if you’re making a full-color map), I would recommend building out a low resolution version of the entire world, then building out higher resolution continents, using the low resolution image for the ocean floor, and adding the higher resolution continents onto the map in Photoshop.

Another consideration I’ve just thought of and am editing to add here is that for almost all situations, in almost all applications, much of the ground will be covered in foliage or buildings or other objects that will prevent anyone from seeing any extremely high detail. Thinking about it in the real world, when was the last time you remember seeing individual flow lines in real life? They’re much easier to see in pictures taken from great heights or great distances. It’s only really in regions dominated by bare rock or sand that we really start to see fine detail on a personal human level. Once dirt and/or grass/plant life get involved, they really have a smoothing effect on a terrain as a whole.

There are a million other considerations to make when looking at planetary scale projects, but this is just everything that came to my mind first for every application I could think of. I’m sure you would get more responses if there was a bit more detail. If nothing else, knowing the specific type of project as well as any technical limitations, time restrictions, and/or available resources could be extremely helpful in suggesting a course of action. Are you working from a detailed design doc, do you have any sketches to work from, are there any specific features that need to exist, do you have any other software that could help give you a running start such as Photoshop and/or Illustrator, is this meant to be fully procedural with no significant art direction, do you have a deadline or is this a hobby/personal project, what kind of computer are you using to build this terrain? All important questions that will influence the recommended workflow. Realistically, the way the question is worded currently would be like going into a filmmaker’s forum and saying “I want to make a feature-length film. Any suggestions?” Love to see the enthusiasm, but need more information if we’re to be truly helpful here.