Re: [Flightgear-devel] osm2city.py

[Thomas A. <ra...@we...>]

James,

> Could the floor-plan data be pulled live from OSM servers, or does it need to
> be processed offline before hand? We have most of the infrastructure to pull
> data from web-services already in place.

Currently data is processed offline before hand. Basically, it parses the OSM
xml, generates a list of building outlines, discards some based on their area,
simplifies the outlines, clusters them into ~500x500m blocks and different LODs,
then writes .ac, .xml, and .stgs. OSM parsing is by far the most expensive,
easily taking 10 minutes for 50k buildings. Once that's done, the remaining
parts take maybe 1 minute in total. In C++, this would be faster, of course. Are
you thinking of a terrasync-like thing here, where users get OSM buildings
(where available) on-the-fly? In addition to what Stuart said, this might be
quite expensive in terms of bandwidth. The OSM download (buildings only!) was
~40MB for the 25x25km LOWI area.


Curt,

> Would this data set include airport hangar buildings as well?

At the moment, the code knows only the floor plans. No streets, no runways, no
land-use. But it'll certainly process such data in the future, and then could
use some heuristics (some OSM buildings are labeled "Terminal 1" or so) to apply
terminal/hangar textures to buildings at airports. Hadn't thought of this
before, but yes, this way we could rather easily populate some airports with
'semi-generic' terminal/hangar buildings.

Stuart,

Thanks for pointing me at fgelev. I'll give it a try.

If I had a limited number of "complex" (as in > 8 vertices per model) shared
models, and place a total of 50000 instances in a scene, could this be made to
occupy significantly less RAM than 50000 individual models? 


Gijs,

Thanks for your comments! I'm aware that OSM building coverage is basically
non-existant in large parts of the world. Street coverage is much better, that's
why I also aim at procedurally generating cities just from a street network.
Meanwhile, a forum user (vanosten,
http://flightgear.org/forums/viewtopic.php?f=5&t=17598) who's interested in
exactly that offered to join forces. Since I've already invested ~3 months here
and remarkably didn't get bored (in fact, quite on the contrary), I'm confident
we'll get there eventually ;) I know of bob.pl, but I just cant read perl... 

> When there are buildings, you'll often find that they are drawn as big blocks,
> rather than individual houses.

True, unfortunately. Plus, _if_ there are many tiny individual houses, they'll
kill framerate (backed by some experience with LOWI now). Appropriate textures
might help here.

> Before I could create some sensible buildings for New York I had to add height
> tags; all skyscrapers were simply lacking that data. 

Why not simply assume a sensible distribution of buildings heights in this case?
I've played with that some days ago, and found it looks quite reasonable:
http://ubuntuone.com/0X0KcYJbRgUtIldtasWyMo
http://ubuntuone.com/1LaEKT6pOtf6zxXItpKmPA
http://ubuntuone.com/0jsCECjmKMaooP4wrHHwH7

Thomas