"Kenneth" <kdw### [at] gmailcom> wrote:
> What I've noticed from looking at real city images (well, using New York City as
> my guide-- a *mostly* grid type of layout), the street widths and their block
> sizes are interesting: The main thoroughfares are wide and long, while the cross
> streets are narrow. And the city 'blocks' between the narrow streets have only
> two buildings back to back (of various ground plans, of course, along with an
> alleyway), while the wider streets are much longer, with many more buildings
> along their lengths. In other words, the street-isolated blocks of buildings are
> not square, but rectangular. (Older thoroughfares like NYC's Broadway go in a
> diagonal direction, but that's another matter!!)
>
> That's my plan for my own city, anyway-- when I finally get around to coding it

I have had these exact thoughts :)

The lines I use as input for streets also have widths associated with them. I
have some convoluted magic that fairly reliably makes the resulting block
polygons with the correct gaps between them. When making buildings, there is
also a max alley width used to separate them. I've even gone as far as flagging
polygon edges that lie on street lines, which is carried through to the
buildings. This enables me to discard buildings that are hemmed in with no
street access (just about visible in the hill-downtown image), and in theory I
can make the 'blocked' building faces differently (e.g. fewer windows). If I set
the split parameters right, I can get back-to-back blocks, but you do see larger
blocks with empty interiors in real cities elsewhere in the world.

(I think I'm low-balling the street widths, because they're hardly visible in my
images here unless the camera happens to be aligned with them.)

And it's funny you should mention NYC - I actually have an approximated SVG
version of Manhattan that I hand-traced over Google Maps screenshots, each
street a single line. I've been using it for testing. I've only tried it once
recently - it took minutes to process and the resulting building geometry files
were > 250MB :o I'll have to try it again soon to see if I can get some
interesting images :)

Bill

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