I attach the latest version of Nimitz. The textures have been improved. A glide-path has been added, it is on by default, but can be switched off by means of the properties browser: /ai/models/ship/controls/glide-path. The origin has been adjusted to the turning pivot and approximate roll center.
Modified AiShip files are also attached. These allow the radius of the turning circle of a ship to be input. The turning circle is adjusted for speed and rudder angle. Roll has been corrected so that a ship leans out of a turn, not inwards like an aircraft. The roll angle is adjusted for speed and rudder angle (yes, application of more rudder reduces roll angle - rudders act as stabilizers).
TODO
Add a relative wind calculation so that a carrier can be turned to the appropriate launch and recovery courses.
Add a 'flight plan' so that the carrier can carry out a racetrack for flight ops.
Add a projector landing sight.
Add auto-land facilities.
Here are files to get automated contrails working. I've set up contrails for
the 737, using my simple, untextured contrail model. Vivian has made another
contrail model, but I'm still trying to get his to work. I'm hoping others
will try to make contrail models also.
Here's some code that defines a top to thermals. When the top of a thermal is
reached the strength is phased-out linearly over the next 100 feet of
altitude. At first I tried just capping the thermal at the top, but the
change in thermal strength was too fast for the FDM to handle well.
Included is a new version of the thermal scenario that includes a top
(height-msl) to the thermal. The default value is 5000 feet.
As a result of recent requests, I've implemented the ability to switch off
aerodynamic stabilisation:
This has to be added to the submodel.xml files:
<aero-stabilised>false</aero-stabilised>
When false the submodel retains the pitch given at instantiation.
It defaults to true.
I think I found the problem in props.hxx. I have an exception when copying properties. An alias to a property that has no value trigger this exception. The code that generate that is in AIManager.cxx :
void FGAIAircraft::bind() {
FGAIBase::bind();
props->tie("controls/gear/gear-down",
SGRawValueMethods<FGAIAircraft,bool>(*this,
&FGAIAircraft::_getGearDown));
props->getNode("controls/lighting/landing-lights", true)
->alias("controls/gear/gear-down");
}
controls/gear/gear-down has no value ( _type == NONE ) and controls/lighting/landing-lights is copied somewhere.
Erik:
Frederic's fix was to change props.hxx but he has expressed his doubts.
For now I've commented out the line that causes the problem so we have more
time to look deeper into the problem.
cvs -z4 -q diff -u props.hxx (in directory I:\FlightGear\cvs\SimGear\simgear\props\)
Index: props.hxx
===================================================================
RCS file: /var/cvs/SimGear-0.3/SimGear/simgear/props/props.hxx,v
retrieving revision 1.4
diff -u -r1.4 props.hxx
--- props.hxx 19 Sep 2004 09:08:12 -0000 1.4
+++ props.hxx 21 Oct 2004 07:10:54 -0000
@@ -622,7 +622,7 @@
/**
* Test whether this node contains a primitive leaf value.
*/
- bool hasValue () const { return (_type != NONE); }
+ bool hasValue () const { return (_type != ALIAS && _type != NONE) || (_type == ALIAS && _value.alias->_type != NONE); }
/**
I've finished the variation of Cd with Mach number.
The calculations are only applicable to ballistic
objects, and then strictly one shape: non boat-tailed bullets/shells, so
I've put them in AIBallistic rather than AIBAase. For all inputs, Cd
should be the sub-sonic value, so bullets will need changing.
I've just posted a graphical analysis here:
http://myweb.tiscali.co.uk/vmeazza/FlightGear/cd_mach.pdf
The calculation of submodel mass from weight has been moved from AIBallistic
to Submodel so that it is calculated only once, rather than on every
iteration as a present. The parameter <contents> has been added, primarily
so that droptanks will have the proper mass. It is the path to an
appropriate property containing a weight in lbs.
Care has to be taken with the use of <contents> because after a reset there
appears to be a delay in submodel instantiation (dt not properly reset???)
and the weight property is not always picked up before it is set to zero in
the key bindings. Slightly hard to explain. It works fine if FGFS has not
been reset though. There is a partial solution which involves the rejigging
of the fuel and gui nasal scripts, but there is still the visible delay in
instantiation to be resolved. I've nearly done the nasal fixes, which will
form part of an update to the Hunter only. I'll probably complete those
later today.
The value of rho (air density) varies with height. (Including the upper
stratosphere, ust in case someone wants to model ICBMs.) The standard
atmosphere is used (based on a sea-level temperature of 15 deg C.).
Erik Hofman:
I moved this code over the AIBase::update() so all AIModels can make
use of rho, temperature, pressure, etc.
I have added <Cd> and <weight> to the input parameters in the submodels.xml
script. Raw data may be used, thus avoiding the need to guestimate <eda>.
Eda remains, but should now be used to enter the proper cross-sectional
area.
I had to reverse a number of signs to get it right. I took the opportunity
to add roll to the submodel so that droptanks will come off with the right
orientation. I have neither added the rotational speed to the submodel, nor
yaw, so if you release droptanks with significant roll rate or yaw angle on
the aircraft the submodel will not be quite right. Straight and level, or
nearly so, is fine.
The maths, so far, is now correct. Roll and pitch are now both in the
correct sense. The aircraft velocity is added correctly to the
submodel velocity, and the submodel is now visible when instantiated.
However, the velocity is measured at the aircraft centre. To be totally
correct we ought to take into account the aircraft's rotational
velocity. We have pitch rate and roll rate available, but not yaw rate
(small anyway).
I've added another parameter to the submodel - wind.
It's activated by the entry <wind>true</wind> in the ../submodel.xml file.
If true, the submodel is affected by the local wind, otherwise not. The
parameter defaults to false. This is useful for exhausts and smoke, and
possibly all objects.
Attached are the modified files to add buoyancy as a parameter for a
ballistic object. It may be set by adding
<buoyancy>x</buoyancy> to the submodel .xml file, where x is the appropriate
value (ft per sec2):
32 neutral buoyancy - contrails
>32 positive buoyancy - exhaust plumes
(0 non-op - default value)
If <buoyancy>x</buoyancy> is not used, then there is no effect on the
current ballistic model
Silly me. I was starting the timer at zero, so the first tracer didn't fly
until 0.25 seconds after pulling the trigger. Now the timer starts at the
same value as "delay", so the first round comes out immediately.
Also, I've added an optional configuration attribute that allows you to change
the ballistics of the submodel. This allows parachutes, or anything else
that has ballistics different from a bullet. The attribute is called "eda",
which is the equivalent drag area. Default value is 0.007, which gives the
same ballistics as the current tracers. Increasing this value gives more
drag. A value of 2.0 looks good for a parachute.
math stuff
########################################################################
The deceleration of the ballictic object is now given by:
[ (rho) (Cd) ] / [ (1/2) (m) ] * A * (V * V)
where rho is sea-level air density, and Cd and m are fixed, bullet-like
values. So the calculation is:
0.0116918 * A * (V * V)
The value "A" is what I'm calling the "eda" (equivalent drag area).
########################################################################
A parachute model will have to be built so that the parachutist's feet
are in the forward x-direction.
Here is the submodel.xml config I use for "parachutes":
<submodel>
<name>flares</name>
<model>Models/Geometry/flare.ac</model>
<trigger>systems/submodels/submodel[0]/trigger</trigger>
<speed>0.0</speed>
<repeat>true</repeat>
<delay>0.85</delay>
<count>4</count>
<x-offset>0.0</x-offset>
<y-offset>0.0</y-offset>
<z-offset>-4.0</z-offset>
<yaw-offset>0.0</yaw-offset>
<pitch-offset>0.0</pitch-offset>
<eda>2.0</eda>
</submodel>
I've included the latest fixes to the Traffic Manager/AI flightplan generation
code. Most of the code changes are in AIFllightplan.cxx. This is the code
that runs without depending on predefined FlightPlans in
#FG_ROOT/Data/AI/Flightplans.i
As suggested by Dave, I've also added a new property in
preferences.xml: /sim/traffic-manager/enabled, which is used to control
whether or not the traffic manager is active.
I'm still working on a few more 737 traffic patterns, those are going to take
a little longer, so I didn't want to wait sending in this code.
Finally, I haven't put much effort into ensuring "aeronautical correctness" in
this version yet. The code works on my system, but what the AI plane do may
actaully be quite rediculous. But I'd like to leave that for the next
version.
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.
