Variations

I've always planned Undiscovered Worlds to be not simply a map generator but a world generator, with - ideally - a quasi-realistic sci-fi sort of feel. At the moment it's creating maps of what are effectively alternate Earths. But I'd like to create more variety in the kinds of worlds it can create maps of.

To some extent this has already happened. When I rewrote the continent creating functions, I didn't delete the original ones. They're still in there as a possible variation, so while most worlds use the newer version, a few will still use the original. The original's not as good, but it's worth keeping for the sake of variety.

So in that spirit I've been working on expanding the range of possible worlds that UW can create.

First, worlds of different sizes are now possible. In addition to the roughly Earth-sized worlds that already exist, you can have worlds with a quarter of the surface area (roughly Mars-sized) and worlds with a sixteenth of the surface area (roughly Moon-sized). (Other sizes aren't really possible thanks to the limitations of the diamond-square technique, which I use extensively.)

With worlds of varying sizes come variations in gravity too. In fact gravity can now be anything from 0.05g to 10g. On low-gravity worlds, mountains are taller and wider, while river valleys are wider but shallower:

On high-gravity worlds, by contrast, mountains are small and river valleys are narrow but deep:

In addition to size and gravity, there are several new variables, which mostly affect the climate in various ways:

I've extensively rewritten the climate simulation (again), which really ranks up there with lakes as one of the most gruelling elements of this whole thing. The problem with climates is that there are so very many moving parts that any changes to one element can have knock-on effects with all sorts of other things. This time, I had to rewrite it so that it could handle (with sufficient plausibility, if not real accuracy) not only Earthlike conditions but a huge range of other possibilities as well. Still, I think it worked out just about OK.

The simulation can now handle quite dramatically different circumstances, which can be caused by variations in the planet's orbit. Obliquity, for example, refers to how tilted the planet's rotation is compared to the plane of its orbit around the sun. Earth's is roughly 22.5 degrees, and this is what causes our seasons, as different parts of the planet are angled towards the sun at different times of year. Relatively modest changes to obliquity can yield dramatic results. At low obliquity, there is little or no seasonal change throughout the year, which means no continental climates or subpolar regions, and you tend to get lots of rainforest, deserts, and temperate oceanic regions. At higher obliquity, the seasons get more and more dramatic. Not only that, but as the obliquity gets higher the poles get hotter, because they are spending more of their time pointing towards the sun. At the highest obliquities, the poles are actually hotter on average than the equator, though they experience huge shifts in temperature throughout the year. The equator, meanwhile, has two summers and two winters in every year.

Here's a world with high obliquity, showing permanent sea ice at the equator but not the poles!

Eccentricity, meanwhile, is how elliptical the planet's orbit is around the sun. Low eccentricity means a roughly circular orbit, while high eccentricity means a highly elliptical one like a comet. Earth has an extremely low eccentricity, which means that it is roughly the same distance from the sun all the time. But a planet with a high eccentricity would experience hotter temperatures for part of the year, as it comes close to the sun, and then colder temperatures as it swings away. Moreover, because planets in such orbits move more quickly the closer they are to the sun, the hotter part of the year would be shorter than the colder part, with this effect being more noticeable at higher eccentricities. So with high eccentricities, you get global "seasons" - but the "summer" is shorter than the "winter". To make things more confusing, the "seasonal" difference is greater at the equator than at the poles, rather than the other way around as with seasons caused by obliquity.

Things get really confusing if you raise the eccentricity and the obliquity. Depending on how high you set them, you get a world with seasons similar to our own but where one hemisphere has a short, hot summer and a long, cold winter, while the other has a short, mild winter and a long, mild summer (Mars experiences something like this, to a moderate degree). Here's a world like that:

Finally, all of these new variables are controllable by the user as well. It's now possible to create custom worlds where you specify the size of the world, the approximate proportions of land and sea, and the variables shown above. So you can create worlds with really exotic climates if you want to, or specify worlds with exactly the same variables as Earth or only slightly different, or have an ice-bound moon with an ocean below the surface.

There are still some wrinkles to iron out with all of this, and then the next plan is to create some new terrain types that might be appropriate for worlds that don't resemble Earth so closely.

Undiscovered Worlds now downloadable

After much additional tinkering, I've posted the latest version of Undiscovered Worlds for anyone to try out. Full details are on the first post of the blog. Many thanks to Frank Gennari for his help with bashing this into something approaching presentable shape!

There are still various bugs, so approach with caution, but I hope people find it interesting to play with!

Even smaller update

Just a quick post as I don't want to leave the somewhat downbeat previous post as the last one for too long... With some much-appreciated help it's become clear that NanoGUI, which I was using for the UI, is ridiculously difficult to get working in different development environments. So I've given up trying to do that, and I'm rewriting using Dear ImGui instead. This is a shame as (a) it means I have to rewrite, and (b) NanoGUI is so pretty, and I will miss it; but it's worth it to get the thing to work properly. Dear ImGui is much more intuitive to use (and vastly better documented), so I'm hopeful that this shouldn't be too monumental a task, but we shall see!

Impasse and need for help!

More bug squashing! This included three entirely distinct lake-related bugs that all coincided in a single regional map. I really hate lakes. I've also made a few more refinements along the way that are too minor to detail.

A couple of recent screenshots:

Anyway, what this means is that I've pretty much finished this stage of Undiscovered Worlds. As I said a million years ago, I envisaged a long-term project in three stages:

1. terrain generation
2. flora and fauna generation
3. civilisation generation

I don't know whether I'll ever get to (3) - and really it's the one that interests me the least right now, especially as so many other people have done it so well - but I do think that (1) is pretty much done now. It's certainly not perfect but it's as good as I can plausibly get it, at least in the foreseeable future.

So I'd like to release this now. I'm planning on putting the source code up on GitHub so that anyone can tinker with it and make it better. I'd also like to make executable versions available so that less technically minded people can use it too. However, there are a couple of problems with this:

1. The project uses several external libraries: NanoGUI, SFML, and stb_image. Somehow I've installed these in some eccentric way that allows my code to work fine on my computer, but I can't build an executable that will run anywhere else, because it won't incorporate at least some of these libraries. The fact that I can't manage what ought to be a fairly elementary part of development should indicate my skill level at this sort of thing.
2. This project is written in C++ using Xcode on a Mac. Even if I manage to solve problem 1, I'll only be able to create an app that runs on Mac. It would be nice to be able to make it for Windows and Linux too, but I don't know how to do that.

So I need some help! - from either somebody who can walk me through solving these problems, or, perhaps more plausibly, somebody who can build the executables themselves if I make the source code available. Is there anyone who might be willing to help?

[EDIT] I've put the source code on GitHub - you can see it in all its ghastly glory here.

Small update

I've been doing a fair bit of unglamorous bug squashing and general tinkering. Much of this is behind-the-scenes stuff that just makes the code work a bit better and hopefully crash less often, but there are also some visible effects, mostly at regional level:

• Some river-related bugs have been removed. Plenty remain, naturally.
• I made some additional tweaks to the climate simulation, to reduce the amount of desert slightly.
• A long time ago I implemented canyons, which work by creating wide areas of the map where the land is raised up higher than usual around the river valleys. Somehow the effect of these was much reduced when I ported the project over to its current form. I've now made it much stronger and more noticeable.
• In addition, some of the smoothing routines applied to the regional terrain tended to widen canyons in an unpredictable way which made them look weird. I've stopped that, so now river valleys really look like river valleys.
• I worked out why - as noted in the previous post - some coastlines had acquired extravagant islands (it was to do with changes to how the sea bed is generated), and toned it down so it only happens sometimes.
• I also removed a tendency to create lakes right by coastlines, noticeable in (among others) the last image here.

Here are some pictures, in which you can see the river valleys more clearly in some areas, as well as varied coastlines. I think the texture of the land is looking pretty nice now:

And as a bonus, here's an epic river system:

Grids revisited

A while ago I posted about a problem with grid-like artefacts cropping up. These are an unavoidable side-effect of relying so heavily on the diamond-square algorithm for generating detail on the regional map: that algorithm is known for a tendency to look a bit grid-like.

Back then I came up with a rather elaborate solution for this problem which involve blending the terrain with a warped fractal. However, while this did eliminate the artefacts, I found that it tended to flatten the terrain too much and remove much of its texture, so I turned it off. That still leaves the artefacts problem.

Here's an uncommonly severe example:

While it doesn't usually look quite this bad, even occasional examples as horrible as this are unacceptable. I've found that this problem usually occurs in coastal areas where there are lots of rivers and a few ranges of hills or low mountains, so this is a typical sort of map to have this problem.

It occurred to me that rather than messing about with adding interference to the terrain to try to mask the grids, there could be a much simpler method. For each tile, I take a random point on each side. I then mark out a circle (with a radius equal to the width of a tile) centred on each point. Then I simply rotate that circle by a random amount. The rotated circle is progressively blended into the original (the closer to the centre it is, the more strongly it's the rotated version; the closer to the edge, the more strongly it's the original). And that's pretty much it. This is done after the basic land elevation is generated, but before the hills and mountains are added, so they aren't affected. Also, for obvious reasons we don't alter any points that are on - or bordering - rivers or lakes, or sea.

Much to my surprise, this not only worked exactly as planned the very first time I tried it but yields what I think are really nice textures for the maps. Here's what the area above looks like with this technique in place:

This is clearly a big improvement - the grid-like features of the original are almost entirely obliterated, but without making the terrain flatter and less interesting. Instead, the texture is more finely grained, while still keeping the general areas of high and low ground in place. (And don't ask me where all those islands have come from - I must have made some other change that caused those, but I can't think what.)

Here are a couple more maps to show off this general look:

As you can see, the new effect is most noticeable in the green areas with high rainfall and more rivers, but it shades nicely into the more arid regions and mountainous areas which are both sometimes associated with the more terraced look you can see in the last two images (and which is applied after the rotation effect). So we've got a bit of variety in the appearance of our maps, which is always good.

Volcanoes

In his very influential post on map generation, Martin O'Leary commented that one thing he'd like to see done was volcanoes. So I've added volcanoes.

There are lots of different kinds of volcanoes, but for our purposes we'll just distinguish between shield volcanoes - which are broad with shallow slopes (such as those on the islands of Hawaii) - and stratovolcanoes - which are tall with steep slopes (such as Vesuvius). Most volcanoes are stratovolcanoes.

We can also distinguish between volcanoes that occur at boundaries between tectonic plates - more specifically, where oceanic plates are pulling away from each other (e.g. the Mid-Atlantic Ridge), and where oceanic plates are subducting underneath continental plates (e.g. the Andes) - and hotspot volcanoes, which are much rarer and occur just about anywhere.

It's easy to add volcanoes in mountain ranges that are drawn along the edges of continents. They don't stand out, because they're part of mountain ranges, but they're there. Hotspot volcanoes take a little extra work. For one thing, hotspot volcanoes often have extinct volcanoes nearby, because of the movement of the tectonic plate over the hotspot beneath. So UW creates those too. There isn't any functional difference between an active volcano and an extinct one other than that if you click on the crater of an active volcano it will tell you it's a volcano.

Stratovolcanoes appear as isolated peaks, with perhaps a subsidiary peak or two with their own craters. Here's a line of them - the one to the southeast is active, while the others are extinct volcanoes formed by the same hotspot in earlier ages:

They look pretty small on the regional map, as you can see, but bear in mind that this map is at a scale of one pixel per kilometre. Compare the scale and general shape of Vesuvius, and I think these are about right:

Shield volcanoes, meanwhile, are done by raising the land round about to create a wide, gradual slope, surmounted by a relatively low peak with a system of nice buttresses around it. These are much rarer than stratovolcanoes but can be quite impressive features when they do appear:

And here is a chain of shield volcanoes. The one furthest to the east is the active one, and the others are extinct. I like how lakes have unexpectedly formed on the slopes of this volcanic range (the active crater is just to the east of that lake in the centre of the last volcano):

(I know it looks like that river is going over the flank of the volcano to the west - it isn't really, it's running through a canyon between the volcano and the hills just to the west.)

Submarine volcanoes are also important, and we create them in a similar way to stratovolcanoes on land, with solitary peaks rising from the seabed. Again, the ones around the oceanic ridges mostly blend into those ridges, but the ones in other areas are more noticeable, especially if they have chains of extinct seamounts associated with them. Hotspot volcanoes are more common in the oceans than on land - unsurprisingly as oceanic crust is thinner than continental - and they tend to clump in particular areas, so UW models that too. Sometimes these rise above sea level and create volcanic islands:

Here's a close-up shot of some islands I liked - the large island has a stratovolcano in the middle, with three active craters. The whole island is covered in tropical rainforest. Clearly a good place to bury some pirate gold.

And of course the import feature now lets you import volcano maps, so you can add them to your custom worlds. This means that Mount Doom and the Lonely Mountain can be added properly to Middle Earth, which is clearly a major step forward.

Gondor came out a bit nicer this time too!