Howto:Make an aircraft: Difference between revisions

{{stub}}

The content in this article gives a summary of codes and can be found on most planes. So, for examples on how it's used, you can take a look at some random planes.

Additional information is available in a [http://www.flightgear.org/forums/viewtopic.php?f=4&t=6030 special forum topic].

# The '''appearence''' of the aircraft, which can be split in two areas:

## 3-dimensional model and all of its visual aspects: animations (These give visual feedback from your FDM. Move the aileron of your 3D model when the aileron control is moved. Same for the other aero surfaces, the gear. Than go ahead with the instruments, animate the needles, the digital readouts. Define hot spots and pick animations, so you can click in your 3D cockpit.), [[Howto: Add aircraft lights|lighting]] and textures (images that are put in specific locations on the 3D model).

## auditory (sounds).

* All images in FlightGear should be sized to powers of two (eg. 64*64, 128*256 or 16*1024). Since FlightGear 1.9, images no longer have to be saved in the .rgb format. Right now .png is most common used among FlightGear developers.

* Please note that we use spaces in our codes, some developers use rather tabs, to make our code easy(er) to read. Every line that starts a new tag, we press the space key once, so you get a kind of stairs. It does not really matter what method you use, as long as you use it consistently throughout all of your files.

* Filenames and directories are case-sensitive on most OS's. Windows is not case-sensitive, so when you are developing on a Windows machine, you won't notice any problems. On other OS's, there is a difference between 'Boeing' and 'boeing'. Since FlightGear is used on multiple platforms, make sure your code makes correct usage of capitals.

If you realize this is harder than you expect, don't worry. For the first-timer, the FDM(aircraft.xml), aircraft-set.xml, and the engine.xml files are the easiest. Modeling will require considerable time and practice. You want to have the tools for the job, so here are some tools to help:

* your patience

The data created during development results in many files, which are stored in several directories per aircraft. Each aircraft has its own directory in the <tt>$FG_ROOT/Aircraft/</tt> directory. The first thing to do when you start working on a new aircraft is to make a directory for it. A short version of the aircraft name (eg. harrier), or its serial number (eg. 747-400) is prefered. More directories might be needed further on, but we will create them when we need them. They are explained in this article, but you can skip them if you are working on your first aircraft. For now we create one directory, namely:

* <tt>Models/</tt> all files related to the appearence of the model are saved in this directory.

* '''Hint for Developers:''' You can pre-test all your .xml files without having to load FlightGear by opening them with Internet Explorer or Mozilla Firefox. These web browsers will parse XML documents and let you know if you made a mistake coding them.

This file contains the entire (or partial) [[Flight Dynamics Model]] of the aircraft. We have three different systems; they all have their up- and downsides.

* [[YASim]], needed for: helicopters, towing over a [[Howto: Multiplayer|multiplay network]]

With limited data available, YASim is generally considered to be the best way to go. When you have acces to real windtunnel data and/or require more flexibility, JSBSim might be a better choice.

This is the most important file of a FlightGear aircraft. This is the only file that is read directly by FlightGear. Actually it can be compared with an airport hub (from where flights of a certain airline to all other airports departure and arrive). The -set.xml file leads FlightGear to all files that are needed to simulate the aircraft. The -set.xml file should be stored in the aircraft's root directory (eg. <tt>$FG_ROOT/Aircraft/747-400/</tt>)

The following tags are to be placed between the <sim> and </sim> tags.

The text that is to be shown in the aircraft selection dialog of [[FGRun]] and other GUIs.

Commonly shows the latest update date.  

The status of the development of your plane. This can for example be used in order to get a list of aircraft with a certain minimum development status by passing the --min-status= parameter to the fgfs executable.

* production

Place your name(s) here. If multiple people worked on the same aircraft, you can place the specific development area for each person between ( ).

What FDM system is the aircraft using. Set to 'yasim' for [[YASim]] and to 'jsb' for [[JSBSim]].

The filename of the FDM file, without .xml. You have created this file earlier on at: [[#The .xml file (FDM)]]

Adds small text (above the splash texture) to the loading screen.

Where to find the model. Could be an .ac file (plain model format) or .xml if you want to have extras like animations etc.

The path to your aircraft's sound file, do not include if you don't have one. The pitch and volume of the sound is controlled by the xml file and throttle position. If for example you find a nice wav file of the jet engine you're using, you can fix it up with your favorite sound editor so it loops nicely and include that into your model (I've noticed a few models where it can get quite annoying when the loop length is so small you can really notice it) so make it smooth.

Where to find the (2D) panel. We prefer 3D cockpits, which are linked in the model .xml file.

Where to find the [[autopilot]] system.

Only required for JSBSim aircraft. In this directory the engine and thruster/propeller files are stored.

This directory contains all model related files; such as textures, models and animation files (.xml). In the -set.xml file we've set the path to one .xml file. That file should link (indirect) to each other model file (including a possible 3D cockpit) needed for the plane. The whole plane could be modeled into one file, but most developers prefer to split things up. A cockpit for example can be built up by several files, each existing of just one [[Creating instruments for FG|instrument]] or panel. This way it is easy to (re)move certain parts of the aircraft. You set up your model file like this:

A common subdirectory is the <tt>Liveries/</tt> one, which holds the livery files. See [[Livery over MP]] for more information about that subject.

A helpfull feature in learning how to start the engines of a plane, flying a basic leg etc. is FlightGears tutorial system. It allows you to create a step by step tutorial that guides the user through a certain procedure. It can even indicate what switches should be pressed!

More about the tutorial system can be found at [[Tutorials]].

We can place extra information in XML files, that will be ignored by FlightGear. Such as descriptions and explanations of certain XML markups, changelogs etc.

<pre> <!-- Last update: 09-10-2007 --></pre>

[[Category:Aircraft enhancement|Make an aircraft]]

[[Category:Howto|Make an aircraft]]