Techniques for street generation in cities

**keithcurtis** · 05-06-2007, 07:19 PM

pyrnadon, you nailed the reason behind the building pattern exactly. I wanted to give the illsuion of detail, but at the same time, knew that mapping every building would be time-consuming, and unnecessary.

Everything in the map was done in Adobe Illustrator, even the texture effects. For a variety of reasons, I wanted to keep it vector-based.

The building pattern is just a pattern of circles, squares and rectangles, rotated at random angles. I didn't want to have them at right angles, since the city is organics in street plan, dictated by the hilly geography. Included is a screen shot of the pattern.

The roads are a trick that is easy to accomplish with Illustrator and similar vector and layer based graphics applications.

Each road is a single line. The entire leayer has an effect (group of characteristics) applied to it, so that evey object on the layer is treated as a single entity. Basically, there's a 3 pt. stroke of dark color, with a 1pt. stroke of light color on top. Since the effect is applied to the layer, it never shows an overlap, all the dark lines are laid down first, and the dark light lines laid down second. Intersections remain clear. There's more trickery involved with the alleys, since they are of necessity smaller roads. Likewise Circles and Squares and other gathering places are achieved by careful placement of layers.

So the layers are (If I recall correctly), top to bottom:

Plazas (shape of plaza with light fill)
Narrow roads (1pt light stroke)
Main Roads (double storke 2pt light over 4 pt dark)
Narrow Roads Outline (Copy of Narrow Roads layer, but 3pt dark)
Plazas Outline (Copy of Plazas, but with 2 pt stroke.)
Buildings Pattern

This gives the illusion of contiguous paved areas outlined by a dark line.

I hope that made sense. It's one of those things that's much easier to show than to tell.

**pyrandon** · 05-07-2007, 08:07 AM

That makes perfect sense to me, Keith. Very, very helpful! Very clever idea to give the illusion of black outlined roads when in fact it's just light on top of dark lines. (Now that you say it, I can't believe I didn't automatically "see" it right off!) This process would also work in non-vector programs such as Photoshop & GIMP. And thanks, too, for the layer rundown!

I have a couple further questions, if you don't mind:

So I'm understanding that you created your random shapes as a file, then turned it into a fill pattern, then applied it, right?

And you did in fact draw your alleys & sidestreets by hand, right? Was that as tedious as it looks?

I am interested in the reasons you decided to use a vector-based program; was it for scalability? From your sample maps page I'm guessing you mainly use Illustrator and only rarely Photoshop for your projects. Can you say a few words explaining why?

Finally, because you say roads follow the hilly georgraphy I take it you layed out the land before you began designing the city? Can you maybe say something about the composition process you follow?

Thanks for the input, Keith; very helpful!

**keithcurtis** · 05-07-2007, 10:41 AM

Originally Posted by pyrandon

I have a couple further questions, if you don't mind:

So I'm understanding that you created your random shapes as a file, then turned it into a fill pattern, then applied it, right?

Sort of. I didn't create a file for it. It's an Illustrator pattern. Just a snippet of vector (in this case) graphics that are defined as a pattern. It's saved in the file itself. The pattern can be edited and that update will propagate throughout the map.

Originally Posted by pyrandon

And you did in fact draw your alleys & sidestreets by hand, right? Was that as tedious as it looks?

Not at all. Once you have the layers and styles set up, its just a matter of drawing lines. The graphic definitions handle all the tedious work. Unless you find drawing lines tedious. Personally, I find it relaxing.

Originally Posted by pyrandon

I am interested in the reasons you decided to use a vector-based program; was it for scalability? From your sample maps page I'm guessing you mainly use Illustrator and only rarely Photoshop for your projects. Can you say a few words explaining why?

Sure. Vector graphics are extremely easy to edit. When working for a customer, I like to have the file in a form that facilitates quick changes.
Scaling, rotation color changes, all of these are easy to do.
I can also output in any resolution the customer might want.
Now, there are some maps that do not lend themselves well to vector composition. Maps that look painted, such as the maps of Ambrethel or Westeros on the sample page require PhotoShop (or other paint program). In these cases, I still use Illustrator to do the typography. Illustrator has superior typographical controls to PhotoShop. After it's all set up, I'll out put the final composited map in whatever format the customer wants.

Originally Posted by pyrandon

Finally, because you say roads follow the hilly georgraphy I take it you layed out the land before you began designing the city? Can you maybe say something about the composition process you follow?

In the case of Tallon, it was an organic process. I decided I wanted a city cut by a river. This allowed me to create a clear demarcation between Haves and Have-nots. Because it was cut by a river on Equatorial land, I decided it needed to be rather sharply graded for drainage purposes. With that in mind, there are some factors that will dictate street patterns.

On the East (wealthy) side, the slope is not so sharp. This, combined with more wealth/resources/labor, means that they could afford to make the streets straighter on the average. They could undercut hillsides, shore up shallow areas, bridge gaps, etc.
The West side is steeper and narrower. Here the roads tend to follow the contour of the land. There are also more narrow roads on the average, and there is no such thing as a promenade or other street that forms a sense of community. It's much more random and chaotic looking. The Westsiders lacked the degree of civic planning of the East.

Where the roads need to climb in altitude, there are two choices. Either the climb can be made slow and gentle by traveling along the contour, switch-backing where possible, or the inhabitants employed stairs. Stairs are more common on the West, where the hill is steeper, and there was less vehicle (cart) traffic.

Every city map (that I design, anyway) requires consideration for needs of a games' action, underlying geography, resources of the inhabitants, building technology, defense, and movement of food and goods.

**RPMiller** · 05-07-2007, 11:14 AM

The view of the city at the top of this page: http://savageearth.net/tallon.html really shows the elevations and exactly what you are talking about. How was that isometric view created? Was that created from the Illustrator file or did you recreate that from scratch? I'm assuming that you didn't use a 3D application to do it which makes it that much more impressive.

**keithcurtis** · 05-07-2007, 11:51 AM

That was a pen and ink sketch done free hand and then scanned in and colored. I have a love of (and utter lack of skill at) architectural rendering in perspective. I know all the rules, but my compositions are lackluster and uninteresting. That's why the shot of the city is from far enough away to make all the buildings so tiny.

There, now you know one of my dirty little secrets.

**RPMiller** · 05-07-2007, 12:22 PM

Actually that does explain a couple things I noticed, but wasn't going to mention because it wouldn't be right for the student to critique the master.

**pyrandon** · 05-07-2007, 03:01 PM

And the award for most helpful set of posts goes to (drumroll, please...) Keith Curtis!

Thanks so much for all your thoughtful, detailed explanations. Very, very helpful to us amateurs!

**keithcurtis** · 05-07-2007, 04:42 PM

Originally Posted by RPMiller

Actually that does explain a couple things I noticed, but wasn't going to mention because it wouldn't be right for the student to critique the master.

Only if the master is a raging egotist. I can always use critique.
Another reason you might see some discrepancies is that the illustration was done years before the final evolution of the map. I'm a tinkerer.

**RPMiller** · 05-07-2007, 05:04 PM

I wish my tinkers were as nice as yours...

The thing that struck me about that illo was the tilt off the castle side of the river. I almost looks like the top of the hill is facing the river and all the buildings and people would be sliding down it. It is obviously a perspective issue more than anything, but it sort of jumped out at me as a 'Whoa' moment when I saw it. Of course I really have no room to talk as I couldn't achieve anything close to that illo if I tried for weeks on end.

**keithcurtis** · 05-07-2007, 10:40 PM

Yeah, the perspective is a little wonky there. I think at the time I drew the map, the ridge that forms the center of the eastern half of the city was not centered on that inner wall. In other words, the landward side of the wall was physically higher than the water side.

I'd re-do it, if I had an infinite amount of time. Nowadays, I would probably look into some 3D software to model the slopes properly, though.

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