FlightGear FAQ

Cameron Moore
cameron@unbeatenpath.net


Introduction

Welcome to the FlightGear FAQ. Here you will find the answers to some questions that are frequently asked on our mailing lists. If you have a question that is not answered here, feel free to ask us on our mailing lists. Enjoy


Table of Contents

1 - The FAQ

1.1 - Where can I get the latest version of this FAQ?
1.2 - Who do I contact if I have comments about this FAQ?
1.3 - What other important documentation should I read?
1.4 - How old is this document?

2 - Distribution

2.1 - Where is the latest distribution of FlightGear?
2.2 - Where can I find the newest snapshots?
2.3 - Where can I fly and where do I get the scenery?
2.4 - Where can I get some different 3D models for my plane?

3 - Compiling

3.1 - Why won't FlightGear compile?
3.2 - I'm using RedHat 7, and ...?

4 - Configuring

4.1 - How do I install new scenery?
4.2 - How do I setup my joystick(s)?

5 - Running

5.1 - Why is FlightGear so slow?
5.2 - Why is my SGI machine so slow?
5.3 - Stuck upside down after "crash"?
5.4 - What happened to the panel, keyboard, etc?
5.5 - Why doesn't audio work properly under Irix?
5.6 - Why do I get an error loading libmk4.so.0?

6 - Hacking

6.1 - How do I design a flight dynamics model for a new plane?
6.2 - How do I import planes from Microsoft Flight Simulator?
6.3 - How do I import BGL scenery from Microsoft Flight Simulator?
6.4 - How do I design or modify a panel?
6.5 - How do I place objects, like buildings, into FlightGear?

7 - Flying

7.1 - Where can I learn about instrument flying and navigation?
7.2 - What is the difference between Aileron and Rudder?

8 - FlightGear v0.7.6

8.1 - Why do I get an error in viewer.cxx about `exit' being undeclared?


1 - The FAQ

1.1 - Where can I get the latest version of this FAQ?

http://flightgear.org/Docs/FlightGear-FAQ.html

1.2 - Who do I contact if I have comments about this FAQ?

First contact the author. If you get no response, send your comments to the flightgear-users mailing list.

1.3 - What other important documentation should I read?

Definitely read the FlightGear Installation and Getting Started document available at http://flightgear.org/Docs/.

Also see the FlightGear/docs-mini/ directory in the source distribution for various other helpful documents.

1.4 - How old is this document?

See the About This Document section at the end of the FAQ.


2 - Distribution

2.1 - Where is the latest distribution of FlightGear?

See http://flightgear.org/Downloads/.

2.2 - Where can I find the newest snapshots?

The best place to get the latest development code is from our CVS repository. See http://flightgear.org/cvsResources/ for details.

Otherwise, you can get relatively up-to-date snapshots of the development tree at ftp://flightgear.sourceforge.net/pub/flightgear/Devel/Snapshots/.

2.3 - Where can I fly and where do I get the scenery?

While the base package only comes with scenery for the San Francisco Bay area, you can currently fly just about anywhere in the world. See the "Additional Scenery" section of http://flightgear.org/Downloads/ for more information or go directly to our graphical downloader at http://flightgear.org/Downloads/world-scenery.html.

Also visit our "Places to Fly" section of the website (http://flightgear.org/Places/) for some help navigating to some awesome locations.

2.4 - Where can I get some different 3D models for my plane?

We currently don't have any of our own models yet, but we have been given permission by several people to convert their models (which where originally intended for use with Microsoft Flight Simulator) to use with FlightGear. See Wolfram's Hangar (http://home.t-online.de/home/Wolfram.Kuss/) for a list of what we currently have available as well as information on how to convert models yourself.


3 - Compiling

3.1 - Why won't FlightGear compile?

Well, that depends. First make sure you are using the appropriate versions of FlightGear, SimGear, and plib. If any of the packages are out of sync with the others, compilation may fail.

The FlightGear Downloads page (http://flightgear.org/Downloads/) should tell you what versions you need if you are trying to compile the latest stable release. If you are using a development snapshot, make sure all three packages are up-to-date.

Also ensure that you have some implementation of OpenGL with glut support with the appropriate header files. Linux users with nVidia cards should make sure you have the latest drivers from nVidia. Other Linux users make sure you have Mesa3D (http://mesa3d.org) and your X server installed correctly. Windows users see http://www.x-plane.com/SYSREQ/v5ibm.html, and Mac users see http://www.x-plane.com/SYSREQ/v5mac.html.

If your problems persist, subscribe to our FlightGear-Users mailing list and let us know what problem you're having. See http://flightgear.org/mail.html for help with this.

3.2 - I'm using RedHat 7, and ...?

Update your gcc packages. See http://redhat.com/errata/ to fix it and http://www.gnu.org/software/gcc/gcc-2.96.html for an explanation why.


4 - Configuring

4.1 - How do I install new scenery?

The scenery archive files (ie. w100n30.tar.gz) should be untarred into the Scenery/ directory in your $FG_ROOT.

4.2 - How do I setup my joystick(s)?

See the README.Joystick file located in the FlightGear/docs-mini/ directory of the source distribution. This document is mirrored at http://rockfish.net/shell/aboutjoy.txt.

If you have a joystick with digital axes, see http://www.unet.univie.ac.at/~a8603365/flightgear.html for a patch to the development version of FlightGear.


5 - Running

5.1 - Why is FlightGear so slow?

FlightGear supports hardware acceleration, but it seems not to be activated. Make sure you have OpenGL libraries installed and configured properly and make sure you have the latest drivers for your video card.

Linux users: If you are an nVidia user, follow their directions on getting your card working. For most other users, make sure Mesa is installed property and ensure that you have the appropriate kernel device drivers for your card. Most people (and distributions) use modules for their video card device drivers; run `lsmod` as root to see what modules are loaded. You should also make sure that you are loading the appropriate modules in your XF86Config and that your video device section is correct. Now try running an OpenGL application (other than FlightGear) to see how it performs. You can try the gears demo from Mesa or something like Quake3.

5.2 - Why is my SGI machine so slow?

First of all, one of the most common mistakes on SGI hardware is to forget to specify --fog-fastest. On most SGI machines the EXP2 shading model isn't hardware supported resulting in frame rates below 1 frame per second (fps).

FlightGear makes extensive use of the OpenGL z-buffer feature,which on most older SGI hardware is only supported in software. This means that the CPU has to do all the z-buffer calculations in addition to the other tasks FlightGear involves (flight dynamics, scenery tracking, pushing commands into the graphics queue, etc). The following features are software rendered on low-end SGI machines (like Indy and Indigo):

This means that running FlightGear with the following options may not even get the desired result:

./runfgfs --fog-disable --shading-flat --disable-skyblend \
--disable-textures --disable-clouds --disable-sound \
--disable-panel --enable-hud --disable-anti-alias-hud

I could even imagine that adding --enable-wireframe doesn't work on these machines (I would be happy to be proven wrong though).

On a machine like O2 the following options give an acceptable result:

./runfgfs --fog-fastest --disable-sound

Since I don't have access to other SGI hardware I can't tell which options would be appropriate for your situation.

5.3 - Stuck upside down after "crash"?

In his infinite wisdom the FlightGear Grand Master decided that planes were to valuable to allow them to be destroyed by novice pilots who seemed to crash a lot. The fact that nobody has bothered to model crashes may have something to do with it too. :-)

The result of this as you have noticed is that with a little practice an ingenuity you can trim the ship to fly inverted along the ground.

The quick answer is to hit Ctrl+U (with the default key bindings) to warp the plane up 1000ft.

For the stubborn people out there: The trick to learn is to roll back to normal (non inverted) do this by nursing the elevator to get to about 500 feet or so and use the ailerons to snap roll 180*. This is all good avionics except for the plane not destroying itself. Remember the controls work in reverse when you are inverted and keep that airspeed up!!!

5.4 - What happened to the panel, keyboard, etc?

If you are using a development version of FlightGear, make sure you also have the latest base package. See http://rockfish.net/fg/ for details on getting the latest CVS version.

5.5 - Why doesn't audio work properly under Irix?

FlightGear (as of June 2001) uses the Portable Libraries (PLIB) for playing audio. The audio queue implementation of PLIB is far from optimal (in fact it's just wrong). This seems to work on other platforms quite well, but Irix expects things to be programmed properly.

There has been discussion about using OpenAL (http://www.openal.org) for the next release of both PLIB and FlightGear. Tests show that the OpenAL audio implementation does the job right, meaning that these audio problems should be gone by then. In the mean time it is best to disable audio on Irix completely (by adding --disable-sound either on the command line or to your $HOME/.fgfsrc file).

5.6 - Why do I get an error loading libmk4.so.0?

With the default installation, libmk4.so.0 is installed into /usr/local/lib. You need to ensure that that path is listed in /etc/ld.so.conf, then run `ldconfig`as root.


6 - Hacking

6.1 - How do I design a flight dynamics model for a new plane?

See http://jsbsim.sf.net.

6.2 - How do I import planes from Microsoft Flight Simulator?

See http://home.t-online.de/home/Wolfram.Kuss/.

6.3 - How do I import BGL scenery from Microsoft Flight Simulator?

See http://matrixsoft.50megs.com/BGL/.

6.4 - How do I design or modify a panel?

See the README.xmlpanel file located in the FlightGear/docs-mini/ directory of the source distribution. This document is mirrored at http://rockfish.net/fg/README.xmlpanel.

6.5 - How do I place objects, like buildings, into FlightGear?

First, ensure that you have v0.7.7 or later, the scenery files where you plan to place the object, the actual model, and the longitude and latitude where you plan to place the object.

Now get the altitude for your point. If you don't want to calculate this yourself, start FlightGear at your location and take note of the altitude. Here's an example command:

fgfs --lat=45.50 --lon=-75.73 2>&1 | tee fgfs.log

The altitude is probably in feet, so divide the starting altitude by 3.28.

Search the output log file for the first occurrence of the string "Loading tile" and take note of the filename. In the above example, the output line looks like:

Loading tile /usr/local/Scenery/w080n40/w076n45/1712601

Copy a 3D model in a format that Plib understands to the same directory as the tile file. Edit the text file in that directory consisting of the tile name with the extension ".ind". The file will already exist if there is an airport on the tile; otherwise, you can create it from scratch. In our example, the filename is:

/usr/local/Scenery/w080n40/w076n45/1712601.ind

At the end of the file, add a new entry for your object, consisting of the word "OBJECT_STATIC" followed by the model name, the longitude in degrees, the latitude in degrees, the altitude in meters, and the heading in degrees. In our example the line looks like:

OBJECT_STATIC Towerax.ac -75.73 45.40 60 0

Save the changes to the .ind file, restart FlightGear, and enjoy.

NOTE: The above information was taken from the following mailing list post: http://www.geocrawler.com/archives/3/11854/2001/6/0/5991409/. See that page if this one doesn't make sense.


7 - Flying

7.1 - Where can I learn about instrument flying and navigation?

http://www.navfltsm.addr.com/ is a very good site for learning techniques for navigation. Check it out!

7.2 - What is the difference between Aileron and Rudder?

There is a bit of info on aileron vs. rudder here: http://www.arundel.net/xplane/html/crosswind.html and http://www.monmouth.com/~jsd/how/.


8 - FlightGear v0.7.6

8.1 - Why do I get an error in viewer.cxx about `exit' being undeclared?

This error cropped up after the release of v0.7.6. To fix the problem, add "#include <stdlib.h>" to the top of viewer.cxx.


About This Document

FlightGear FAQ
$Revision$
$Date$

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Cameron Moore
cameron@unbeatenpath.net