Here's some additions to AI that allow refueling from an AI tanker (the actual
onload of fuel must be handled by the user's FDM of course, this just lets
the FDM know that the user is in position to refuel).
I've added a new class of AIAircraft called "tanker". It uses the same
performance struct as a jet transport. An AI tanker is just like an AI jet
transport, except it uses the already-existing radar data to control the
boolean property systems/refuel/contact. The code change was minimal.
An AI tanker can be created like this:
<entry>
<callsign>Esso 1</callsign>
<type>aircraft</type>
<class>tanker</class>
<model>Aircraft/737/Models/boeing733.xml</model>
<latitude>37.61633</latitude>
<longitude>-122.38334</longitude>
<altitude>3000</altitude>
<heading>020</heading>
<speed>280</speed>
<roll>-15</roll>
</entry>
This puts a tanker over KSFO at 3000 feet, in a left-hand orbit. When the
user gets within refueling range (contact position) then the property
systems/refuel/contact will be true. Otherwise it is false.
The dimensions of the refueling envelope are pretty rough right now, but still
usable. The user must be behind the tanker (ie. radar y_offset > 0). The
user must be at or below the tanker's altitude (ie. radar elevation > 0).
The user's lat/lon must be within 250 feet of the tanker's lat/lon (ie. radar
range_ft < 250). This last requirement is loose because the radar data is
only updated every 100 ms, which is accurate enough for radar use, but
which is sloppy for air refueling. This could be tightened up by increasing
the radar update rate to once every sim cycle.
I'm going to add a light to the T-38 instrument panel that will monitor the
property systems/refuel/contact. This will make it easier to explore the
boundaries of the refueling envelope.
Here's some new AI stuff.
1) AI objects must now be defined in a scenario file, not in preferences.xml
or a *-set file. (Of course this doesn't prevent objects from being created
dynamically, as with Durk's traffic manager).
2) A new demo_scenario file is attached. It creates 3 aircraft, a sailboat,
and a thunderstorm.
3) Objects without flightplans live forever.
4) FGAIShip::ProcessFlightplan() is not yet implemented.
5) preferences.xml should now define only <enabled> and <scenario>
1. Removed aircraft roll on ground.
2. Decreased descent pitch angle.
3. Updated flightplans to include <on-ground>
4. Fixed property indexing, so all AI aircraft have their own property branch
The default value of <on-ground> is false, so you only need to specify it when
on the ground. For takeoff you need to specify <on-ground>true</on-ground>
for the first waypoint, and for the acceleration waypoint. For landing you
need to specify it for the touchdown point and any taxi points.
One problem. WARNING **** There is a bug in the way the property system
works, which causes a segfault, but I don't know if the problem is in the
property code, or in how I'm using it. After an AI object terminates, if you
access the property tree through the property browser the sim will segfault.
Here's the newest AI stuff.
The AIManager at init() creates a new scenario. Right now the
default_scenario is hard coded in, but eventually the AIManager should get
the scenario filename from preferences.xml.
The scenario defines which AI objects will be created. Right now it only
creates AIAircraft, but this is easily extended. The scenario also defines
which flightplan will be assigned to the airplane. Scenario config files go
in data/Data/AI.
The Airplane gets a pointer to a FlightPlan object. Each airplane should get
its own flightplan object, even if two airplanes have the same flight plan.
This is because the flightplan maintains the iterator pointing to the
current waypoint, and two airplanes might be at different locations (for
instance if they were created at different times). The flight plan files go
in data/Data/AI/FlightPlans.
When the airplane gets to the waypoint named "END" it vanishes. The
AIAircraft destructor deletes its flight plan (if it has one).
The last waypoint is a place holder only. I called mine
<WPT><NAME>"EOF"</NAME></WPT>.
I added some things to the AI stuff to improve the AIThermal processing.
Before, all the thermals were processed in order, and the last one overwrote
the prior one. Now, only the data from the nearest thermal is kept. This
way a tile can be populated with many thermals, and (as long as they have the
same diameter) the one nearest the airplane correctly takes effect. This
will make us ready for the next step, "auto-thermaling", where FlightGear's
tile manager can cover a tile with thermals, and set the thermal strength
based on land-use type.
I moved the enumerated object_type to the base class. When an AI object is
created it now sets the _otype variable in the base class. This lets the AI
manager find out what kind of AI object it is dealing with, using the base
pointer. I also added a function isa() to the base class, so the manager can
process objects differently based on their type.
The AI manager now sends AIThermal processing to a different function, where
only the data from the nearest thermal is kept. After the manager processes
all the AI objects, then the results from the nearest thermal are applied to
wind-from-down.
Here's a new batch of AI code which includes a working radar instrument.
I put the radar calculations into the existing AIAircraft class. It was
easier that way, and it can always be migrated out later if we have to.
Every tenth sim cycle the AIManager makes a copy of the current user state
information. When the AIAircraft updates it uses this information to
calculate the radar numbers. It calculates:
1) bearing from user to target
2) range to target in nautical miles
3) "horizontal offset" to target. This is the angle from the nose to the
target, in degrees, from -180 to 180. This will be useful later for a HUD.
4) elevation, in degrees (vertical angle from user's position to target
position)
5) vertical offset, in degrees (this is elevation corrected for user's pitch)
6) rdot (range rate in knots, note: not working yet, so I commented it out)
and three items used by the radar instrument to place the "blip"
7) y_shift, in nautical miles
8) x_shift, in nautical miles
9) rotation, in degrees
The radar instrument uses the above three items, and applies a scale factor to
the x-shift and y-shift in order to match the instrument's scale. Changing
the display scale can be done entirely in the XML code for the instrument.
Right now it's set up only to display a 40 mile scale.
The radar is an AWACS view, which is not very realistic, but it is useful and
demonstrates the technology. With just a little more work I can get a HUD
marker. All I need to do there is make a bank angle adjustment to the
current values.
