Es/FlightGear Newsletter December 2013: Difference between revisions

== Wizard-based Aircraft Creation ==

When it comes to aircraft development, one of the areas that people find frustrating is that features used by aircraft developers will be documented in the Wiki but the examples are so minimal that it can be difficult or nearly impossible to get something working because the published examples are lacking in detail or don't show important variations of how to code the feature.

We've come to the conclusion, the best step towards fixing these issues is to have a set of templates for common aircraft configurations (single engine prop, multi-engine prop, single engine jet, multi-engine jet with co-pilot etc). These templates would have all of the minimal components to compose a "production" aircraft (according to the rating guide).

We've been tossing around that idea for a while, i.e. coming up with project-maintained "templates" for things like aircraft, to ensure that people have some way to get guidance without overly relying on extensive copy/paste programming - we really only need someone to start with a "dummy" aircraft that, with lots of comments and options (Nasal, sound, canvas, help, checklists, tutorials). In fact, it would even be possible to provide wizards to help customize such templates, i.e. to change name/author/status, 3D models, file names (sound, textures).

The idea is that we should have a set of standard aircraft templates, or some fancy means of generating an aircraft skeleton based on some user input. These templates would contain all necessary files and code to implement a simple but complete aircraft of a given configuration (single engine prop, multi-engine jet etc), and possibly stubs for common enhancements.

Standard enhancements (checklists, autopilots etc) could be included as comments indicating where code needs to be added, This would make FG aircraft more consistent, but also help newbie aircraft developers to get of the initial obstacle of understanding how it all comes together. I think this would help us overcome the issue of having so many aircraft in various pre-production states of development.

During the discussion on the forum, we came up with the ideas that we could have a template aircraft and parametrize it dynamically inside FlightGear - after all, it's 95% PropertyList-encoded XML, i.e. can be read/manipulated and written via standard FlightGear/Nasal means - in other words, you could take an existing PUI dialog and turn it into an "aircraft wizard", where the user could specify things like 1) filename, 2) description, 3) FDM type, 4) status, 5) thumbnail and so on - this is all straightforward to do, it just involves setprop() stuff after having read the template into the property tree via io.read_properties(), at which point a simple GUI dialog could be shown to streamline the aircraft development process in a step-by-step manner. Many building blocks exist already, including a file picker dialog - missing stuff can be implemented via Canvas extensions.

Such a wizard woud ideally not be implemented as a "hardcoded" XML dialog, but rather as a Nasal submodule that dynamically creates "pages" for each step in the wizard. None of this is difficult, it really just involves 1) property tree, 2) read/write properties via io.nas and 3) basic Nasal (setprop/props.nas) for modifying the template aircraft.

Such a wizard could also be easily made aware of difference between FG versions, and users could be asked to target a certain version, i.e. to omit certain stuff, like for example Canvas support, or effects etc

A first, very basic, prototype of this is now available, and waiting to be adopted by fellow contributors to help grow this "wizard", i.e. by adding features to it, but also by adding new templates to it, for different aircraft features, such as [[Aircraft Checklists]], [[Tutorials]], [[Walk View]] etc.

Given that most of us are already juggling too many projects, we're also looking for people who would possibly like to get involved in this in some way.  

Coding-wise, this is currently just about 150 lines of very simple [[Nasal]] code, copied together from various other dialogs and wiki tutorials. So knowing Nasal would be a plus, but if you have any other scripting/programming experience, that will do too. So if you are interested in FlightGear scripting and simplifying aircraft deveopment for newcomers, please get in touch via the forum or the wiki.

Continue reading at [[Aircraft Generation Wizard]]...