May/June Lite Entry: Gulf of Malabor

[gilgamec]

The biggest problem I have with my last version (Attachment 13766) is that the rivers on the eastern side of the Gulf don't run through the thin strip of mainland shown on the map; instead, they all originate in the low hills about 100 miles inland. I was hoping for more of a sense that there's a huge continent off to the east of the map we see, so we might get something like a Mississippi running through the hills and into the Gulf of Malabor. This turns out to be harder than I'd like. I've spent the last five days on this, and haven't really been able to get the kind of effect I like.

First, I'm going to separate the "hills" I'm looking for on the northern arm of the mainland from the "mountains" I want to get in the south. The only way to do this is to specify the general course of the mountains in my original sketch:

This gives a lot more heterogeneity in the heights, which looks much better.

I've also settled on simulating the continent to the east by generating a random terrain, running rivers through it, and recording the sizes of these rivers at the edges of the terrain. I then use these rivers as "seeds" for the rivers on the map itself. This gives us something like

I'm still not entirely happy with this. With only a week to go in the Challenge, though, I'm going to have to move on to other things, like the (required) forests and settlements, along with labels and the like.

I'd still like to revisit the rivers at some time in the future, but it might be with the next Challenge, or as a general WIP.

[Redrobes]

This is some great stuff. I was wondering how far you could take it. I was interested in the basin filling bit mainly as I think that can be quite hard to do.

I was wondering whether it might be better to model the area to the east to get a river in and then once it was there then focus on the map with it already seeded. Is that an idea that might work with your technique ?

[gilgamec]

This is some great stuff. I was wondering how far you could take it. I was interested in the basin filling bit mainly as I think that can be quite hard to do.

If you're only filling it with land, then it's pretty easy; I think I'm using the same algorithm as Wilbur, and it is simple to implement and quite fast. If you're going to have basins with water in them, it's substantially harder. I haven't really thought about what would be needed in that case.

I was wondering whether it might be better to model the area to the east to get a river in and then once it was there then focus on the map with it already seeded. Is that an idea that might work with your technique?

Right now, I've put a "dummy" chunk of land to the east to start the large rivers, and you can see that with the two rivers that flow from the edge of the map to the sea. The height field of the add-on, though, doesn't match the mapped bit, and I think that's part of what's causing problems. I'm loath to model the off-map stuff in any detail for the Challenge, though in the future it may be necessary. I suspect that the only way I'm going to be able to get reasonable-looking rivers is to have at least a low-resolution model of the entire continent.

Hmmm...I just realized that part of the problem with the current version is that even the large rivers don't have deltas. Hopefully, if things go well with the other elements (I'm working on naming now), I'll be able to revisit the rivers before next week.

[waldronate]

http://www.ridgenet.net/~jslayton/Fu...ol5/index.html has some suggestions for routing rivers through basins with water.

For accurate river routing and basin filling, you need to have the entire watershed in your simulation.

In my experience, upscaling from a lower-resolution to higher-resolution DEM while maintaining the river network requires the participation of the river network in the upscaling process.

Deltas require sediment transport and water table maintenance. It's an ugly problem to get to look right because the rules aren't completely scale-free. If you take a simulation designed for 1 meter per grid box and scale it to 10 meters per box it starts to look odd, 100 meters per box looks wrong and 1000 meters per box resembles no reality with which I am familiar.

[gilgamec]

In my experience, upscaling from a lower-resolution to higher-resolution DEM while maintaining the river network requires the participation of the river network in the upscaling process.

This doesn't surprise me at all. There's probably a lot of higher-level processes that you'd need to take into account: not only hydrology, but climate and ecology too. I hope, though, that you'd only need to simulate them at a fairly coarse level to get a decent-looking local area.

Deltas require sediment transport and water table maintenance. It's an ugly problem to get to look right because the rules aren't completely scale-free. If you take a simulation designed for 1 meter per grid box and scale it to 10 meters per box it starts to look odd, 100 meters per box looks wrong and 1000 meters per box resembles no reality with which I am familiar.

I've already got lots of scale-free processes, so another one wouldn't be a problem. Anything with multiple z-levels, though, is going to be extremely nasty. In any case, I'm probably still not going to get to it in the next six days.

[gilgamec]

I've done some fiddling with forests to see if I can get a representation that I can live with, and I haven't been able to so far. More work is needed on that.

In the meantime, I've been looking at labels. This is a threefold problem: what features are worthy of labeling, what do we call them, and how do we arrange the labels? For this checkpoint, I'm punting on the third, and just manually arranging them.

Now, the first problem, what features are labeled? So far, I'm labeling only the Gulf itself, the major cities, and prominent mountains. The label for the Gulf is (for now) manually placed. The major cities, right now, are just placed at the mouths of the major rivers. The prominent mountains are found by computing the topographic prominence of each point on the terrain; this essentially gives us the highest "independent" peaks. (This last bit took far longer than I'd like to code up.)

And what names do we give them? Since, as I've already said, I have no real artistic ability, even literary, so I'm not going to try to make up names. Instead, I'll do it procedurally! I grabbed a gazetteer of the world from the Net. The name "Malabor" sounds kind of South Indian to me, so I extracted all of the place names from South India from the gazetteer. I then use them as inputs to a Markov chain name generator. This gives me about a million words, which are chosen (more or less) at random. Short, frequently-chosen words are made "translations" of geographic terms, like "river", "mountain", "city", and so on. Longer words are proper names.

Drawing names on the map gives us

It's not great yet; in particular, the relative font sizes and the rendering need to be substantially improved. Hopefully, I'll have forests going ahead before the next checkpoint.

[Steel General]

When it comes to labeling a lot for me depends on the scale of the map. With this kind of scale I usually just go with major geographic items, important cities/towns/etc. and other major places of interest.

I think what you've done so far is fine, except maybe reduce the glow on the labels a bit.

[gilgamec]

Not much done in the last couple of days, but I figured I might as well post what I have. I've put names on the landmasses and rivers, and removed them from the peaks. I've also added a graticule (from a simple polar projection), and reversed the rendering of the names (it's much better now, I think). Still no forests, though. *sigh*

[Gandwarf]

Looking nice though!

[silverhead]

Wow. Really impressive. I like very much how the rivers are done.