Hi.  I've been thinking of ways in which I could help out with stuff for
FlightGear, given that I don't code in C++.  Other than providing useful
bug reports and the occasional odd suggestion, I thought of getting my
feet wet by working on adding taxiways to airports that aren't currently
given them.  I also thought I might look at airport buildings, taxiway
markers, etc., and at 3D structures for landmarks such as are present in
the San Francisco scenery.

If it's at all worthwhile for me to do this, then I have some questions.

1.  Regarding adding taxiways, I read a bunch of old emails on this list,
and it seems like there's two ways to approach this.  One is David Luff's
TaxiDraw, which (as I understand it) is solely concerned with rendering
taxiways, and produces a table of taxiway information for a particular
airport that's in an appropriate format for insertion into the
Airports/runways.dat file.  The other is fgsd-taxi, a modified fgsd that
produces taxiway layouts not for rendering, but for AI aircraft to follow.
Do I have this correctly?  If so, does it make sense when doing the former
to do the latter, even if the AI is not yet fully implemented, thinking
that then it doesn't have to be added later?

2.  The taxiways that *are* listed in the Airport/runways.dat, typically
for major airports, don't have taxiway identifications listed.  For

A KSQL     5 CYN San Carlos
R KSQL 12   37.511856 -122.249524 138.09  2599    75 NARHN NYVN    0    0 NYVN    0    0
T KSQL xxx  37.511303 -122.249374 134.68  2600    75 YCB
T KSQL xxx  37.510796 -122.250015 134.68  2600    75 YCB
T KSQL xxx  37.511108 -122.251083 134.68  2000   200 YCB

According to the explanation of the format on Robin Peel's site,
those "xxx" should give a taxiway identifier.  I presume that
FlightGear doesn't use them at the present; but I can imagine
that they might be in the future, for ATC or AI, or for default
taxiway signs (in the absence of signs placed as 3D models in the
scenery).  If these are known, such as through an airport chart,
should they be put in?  If so, in what format (e.g. left-justified,
right-justified, zero padded, etc.)?

3.  Where should the taxiway data go?  The TaxiDraw tutorial
mentions sending them to Robin Peel, for inclusion in the complete
airport data.  Is that still the case?  Various things I've read
in the archives here gave me the impression that these days,
FlightGear is compiling its own airport data files from the DAFIF,
rather than getting them from Robin Peel's compilation.  The fact
that the files in Airport/* are similar to, but not exactly the
same as, those described on Robin Peel's website, seem to support
that perception.  Is that true?  If it is, then where should the
taxiway info be sent to, so FlightGear can use it?

4.  Is the information in the airport files considered to be 100%
accurate?  I occasionally see differences between runway lengths
listed in runways.dat and those listed in other sources, such as
U.S. state Department of Aviation databases, or U.S. FAA references
(reproduced at airnav.com).  The differences are rarely large --
less than 20 feet typically -- but it makes me wonder what's right
and whether there may be other discrepancies and so on.

5.  My understanding is that at this point, the runways, taxiways
and aprons are drawn using stock textures for the appropriate type
of surface specified in runways.dat.  Is that correct?  Just out of
curiosity, how difficult is that to change on very small scales,
e.g. for a particular small area at a particular location at a
particular airport.  I can imagine putting in eye candy like
stains and skidmarks and gate markings and stuff like that, such
as one sees in images like:


How straightforward would that be to integrate such things into
scenery?  I wouldn't think it'd be too consuming of rendering
resources, but maybe it would?

6.  What about abandoned airstrips?  Not closed runways, but
airports that don't even truly exist anymore, but can still be
seen from the air.  There's a website at


where a pilot gives info about these things in the US..  I think it'd
be cool to be able to see these from the sky, have them available
for emergency touchdowns, etc.  But I'm not sure whether anyone
else thinks that's a good idea, or what the best way of
implementing them would be (e.g just a model placed on the terrain
at a given point, or with their own listings in runways.dat, or

7.  Are there any guidelines for maximum complexity of 3D models
for scenery?  On one hand, I want to make cool things.  But OTOH,
I don't want to make things which are so cool that they won't get
used because they're too apt to drag framerates down into the

That'll do for starters.  Thanks for any info you can give; hope
my input is welcome.


Chris Metzler                   [EMAIL PROTECTED]
                (remove "snip-me." to email)

"As a child I understood how to give; I have forgotten this grace since I
have become civilized." - Chief Luther Standing Bear

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