Note Whenever possible, please refrain from modeling complex systems, like an FDM, autopilot or Route Manager with Nasal. This is primarily to help reduce Nasal overhead (especially GC overhead). It will also help to unify duplicated code. The FlightGear/SimGear code base already contains fairly generic and efficient systems and helpers, implemented in C++, that merely need to be better generalized and exposed to Nasal so that they can be used elsewhere. For example, this would enable Scripted AI Objects to use full FDM implementations and/or built-in route manager systems.
Technically, this is also the correct approach, as it allows us to easily reuse existing code that is known to be stable and working correctly, . For details on exposing these C++ systems to Nasal, please refer to Nasal/CppBind. If in doubt, please get in touch via the mailing list or the forum first. |
The FlightGear forum has a subforum related to: Nasal Scripting |
Because FlightGear's route manager flight plan system is exposed to Nasal, Nasal can be used to interact with flight plans. Obviously, this is very useful, especially for aircraft like airliners, which have complex route managers systems. This article shows how this can be done.
Background
The Nasal functions relating to the route manager system include:
Flight plans are based on waypoints, which, in C++, inherit from the FGPositioned
(doxygen) class.
Waypoint hashes
The following are members of a waypoint ghost, as generated by, for example, airwaysRoute()
:
- wp_name
- Name of the waypoint, returned as string.
- wp_type
- Waypoint type, returned as string. One of "basic," "navaid," "offset-navaid," "runway," "hdgToAlt," "dmeIntercept," "radialIntercept," or "vectors."
- wp_role
- Role of waypoint.
- wp_lat or lat
- Latitude of waypoint.
- wp_lon or lon
- Longitude of waypoint.
- wp_parent_name
- Name of waypoint's parent.
- wp_parent
- Waypoint's parent.
- fly_type
- How to waypoint should be flown over or reacted to. One of "Hold," "flyOver," or "flyBy."
- heading_course
- Heading of runway.
Flightplan methods and variables
- getWP(index)
- Returns the waypoint for specified index.
- currentWP()
- Return current active waypoint.
- nextWP()
- getPlanSize()
- Returns number of waypoints
- numWaypoints()
- appendWP(waypoint)
- Add a waypoint to the end of the flightplan.
- insertWP(wp, index)
- Pass a waypoint object and its position.
- deleteWP(index)
- Deletes the waypoint at specified index.
- insertWPAfter()
- insertWaypoints(vector, index)
- Pass a vector of waypoint objects, and the position to insert.
- cleanPlan()
- Clears all waypoints including destination and departure.
- clearWPType(type)
- Supply a type string, it will clear all waypoints of the type.
- clone()
- Return a copy of the fligthplan.
- pathGeod()
- finish()
- indexOfWP()
- destination
- airport object as destination.
- destination_runway
- rwy object as destination and its runway implicit.
- departure
- airport object as departure.
- departure_runway
- rwy object as departure and its runway implicit.
- id
- sid
- procedure object for SID.
- star
- procedure object for STAR.
- sid_trans
- star_trans
- approach
- procedure object for approach.
- current
- aircraftCategory
- ICAO aircraft category.
- followLegTrackToFix
- activate()
Leg methods and variables
- setSpeed()
- setAltitude()
- path()
- courseAndDistanceFrom()
Procedure methods and variables
- route(runway)
- Returns a vector of waypoints.
Examples
# get the active flight plan (the one being used by the route manager)
var fp = flightplan();
# or create one an XML file
fp = flightplan('/path/to/xml');
# save the active flight plan
fgcommand("save-flightplan", props.Node.new({"path": 'path/to/xml'}));
# duplicate a flight-plan
var secondary = fp.clone();
var dest = airportinfo('KSFO');
var rwy = dest.runway('19L');
# the the arrival runway (and airport, automatically)
fp.destination_runway = rwy;
# or if no runway is known/specified
fp.destination = dest;
Building procedures and transitions. As mentioned above there's a couple of different ways to handle this, the examples below assume the C++ code automatically deletes and re-inserts waypoints for procedures, but that's only one possible design.
var apt = airportinfo('KSFO');
# example for SIDs, STARs are the same, approaches too
var allSids = apt.sids();
# SIDs for a specific runway - note these return SID IDs as string, for compatibility with existing code
var rwySids = apt.sids('28L');
Inserting and deleting waypoints (possibly in batches)
var fp = flightplan();
# waypoint created from lat, lon, or a navaid, or anything else?
var pos = geo.aircraft_position().apply_course_distance(getprop("/orientation/heading-deg"), 100000);
var wp = createWP(pos.lat(), pos.lon(), "EPICA");
# manually insert a waypoint at the end of the plan
fp.insertWP(wp, fp.getPlanSize());
# manually insert a waypoint at a defined position (n) into the plan
fp.insertWP(wp, n);
# route along airways, and insert a whole bunch of waypoints
# this is needed for the route-manager dialog, maybe not for a
# real FMS interface....
var segment = [<waypoint object>, <waypoint object>, <waypoint object>];
# segment is a vector of waypoints now
fp.insertWaypoints(segment, fp.getPlanSize());
aircraft.history() (3.2+)
Function to expose flight history as aircraft.history()
var hist = aircraft.history();
# get history of aircraft position/orientation collapsing
# nodes with a distance smaller than the given minimum
# edge length
debug.dump( hist.pathForHistory(<minimum-edge-length-meter>) );
Related content
Wiki articles
- Nasal library § Extension functions
- Navdata cache § Accessing via Nasal
- Route Manager
- Route Manager internals
Documentation
- flightplanGhostSetMember — Members of a flight plan object that can be set.
- flightplanGhostGetMember — Members of flight plan object that can be read.
- initNasalPositioned — Contains a list of functions that can be called on airport, flight plan, waypoint, procedure, or flight plan leg objects.
- FGRouteMgr::FGRouteMgr — List of fgcommands relating to the route manager.
Misc
- https://sourceforge.net/p/flightgear/mailman/message/34688624/
- https://sourceforge.net/p/flightgear/mailman/message/35164289/
- https://sourceforge.net/p/flightgear/mailman/flightgear-devel/thread/BB67C9F3-028B-40E5-94E4-246CD1E0B2CC%40mac.com/#msg23708827
- https://sourceforge.net/p/flightgear/mailman/message/33699574/
- https://sourceforge.net/p/flightgear/mailman/message/21010010/
- https://sourceforge.net/p/flightgear/mailman/message/23678747/
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