Hi
here is a patch that YASim gears make use of the ground properties
(friction, bumpiness, etc).
It enhances the gears, that you can define different gears for "on
water" and for "not on water".
And you can define "inverse-speed-spring-is-doubled", with this the gear
extends with increasing speed which can be used for lifting the airplane
out of the water with increasing speed. The friction at this speed is
reduced by "reduce-friction-by-speed" to simulate (fake?) the reduced drag.
This patch is tested only a very bit on default scenery with only one
aircraft. It is probably not ready for cvs. (all enhancements for water
aircrafts are fully untested...) I hope I find the time to test the
beaver in the next days.
Maik
Maik Justus schrieb am 20.12.2006 01:19:
Hi Melchior,
thanks for the info. I will try to make use of this with the yasim gears.
Maik
Melchior FRANZ schrieb am 20.12.2006 00:56:
* Maik Justus -- Wednesday 20 December 2006 00:47:
does anyone know, how to access the ground properties by the FDM?
Looks like the groundcache provides this:
bool
FGGroundCache::get_agl(double t, const SGVec3d& dpt, double max_altoff,
SGVec3d& contact, SGVec3d& normal, SGVec3d& vel,
int *type, const SGMaterial** material, double *agl)
The ground cache is already used by JSBSim and YASim for gear contact.
See simgear/scene/material/mat.hxx for SGMaterial. It has methods to
read friction/bumpiness/...
m.
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Index: README.yasim
===================================================================
RCS file: /var/cvs/FlightGear-0.9/data/Docs/README.yasim,v
retrieving revision 1.17
diff -u -p -r1.17 README.yasim
--- README.yasim 10 Nov 2006 18:06:24 -0000 1.17
+++ README.yasim 21 Dec 2006 00:58:14 -0000
@@ -44,6 +44,15 @@ fuselage: This defines a tubelike struct
expressed as a fraction (0-1) of the width value.
midpoint: The location of the widest part of the fuselage,
expressed as a fraction of the distance between A and B.
+ idrag: Multiplier for the "induced drag" generated by this
+ object. Default is one. With idrag=0 the fuselage
+ generates only drag.
+ cx,cy,cz: Factors for the generated drag in the fuselages "local
+ coordinate system" with x pointing from end to front,
+ z perpendicular to x with y=0 in the aircraft coordinate
+ system. E.g. for a fuselage of a height of 2 times the
+ width you can define cy=2 and (due to the doubled front
+ surface) cx=2.
wing: This defines the main wing of the aircraft. You can have
only one (but see below about using vstab objects for extra
@@ -312,6 +321,23 @@ gear: Defines a landing gear. Accep
unstable. If you can't make the gear stop
bouncing with this number, try increasing the
compression length instead.
+ only-on-water: if ths set to "1" the gear will be ignored if
+ not on water. Defaults to "0"
+ not-on-water: if ths set to "0" the gear will be ignored if
+ on water. Defaults to "1"
+ inverse-speed-spring-is-doubled: At this speed (the inverse of
+ the speed must be given) the spring constant
+ is doubled. The idea is, to use this on water to
+ simulate the speed dependend lift of a float.
+ Defaults to "0"
+ reduce-friction-by-speed: at the speed given by the last tag the
+ friction is reduced by this relative value. Can be
+ used for simulating (fakeing) the reduced drag of
+ a lifted float. E.g. if you secifiy this value to
+ "0.2" the friction is reduced by 20% at the speed
+ defined by the last tag and by 40% at the double
+ speed. Defaults to "0"
+
launchbar: Defines a catapult launchbar or strop.
x,y,z: The location of the mount point of the launch bar or
@@ -481,7 +507,6 @@ rotor: A rotor. Used for simulating h
A value stall gives the fraction of the rotor in stall
(weighted by the fraction the have on lift and drag
without stall). Use this for modifying the rotor-sound.
- The torque property has a bug.
x,y,z: The position of the rotor center
nx,ny,nz: The normal of the rotor (pointing upwards, will be
normalized by the computer)
@@ -555,11 +580,6 @@ rotor: A rotor. Used for simulating h
is stall. In the range between this incidences it is
interpolated linear.
- The airfoil of the rotor can be described in two ways. First you
- can define the needed power for different pitch values and the
- total lift force at a user-defined pitch value. Don't use pitch
- values greater than the stall incidence. You could get strange
- results.
pitch-a:
pitch-b: collective incidence angles, If you start flightgear
@@ -573,6 +593,7 @@ rotor: A rotor. Used for simulating h
coefficients instead (see below) and adjust the lift with
rotor-correction-factor.
+ The airfoil of the rotor is described as follows:
The way is to define the lift and drag coefficients directly.
Without stall the c-lift of the profile is assumed to be
sin(incidence-"airfoil-incidence-no-lift")*liftcoef;
@@ -688,7 +709,11 @@ rotorgear: If you are using one ore more
yasimliftfactor: the solver is not working with rotor-aircrafts.
Therefore you have to specify the results yourself.
10 for drag and 140 for lift seem to be good starting
- values.
+ values. Although the solve is not invoked for aircrafts
+ with at least one rotor, you need to specifiy the cruise
+ and the approach seetings. The approach speed is needed to
+ calculate the gear springs. Use a speed of approx. 50knots.
+ They do not need to match any real value.
The rotorgear needs a <control> subelement for the engine
(ROTORGEARENGINEON) and can have a <control> subelement for the
Index: flight.cxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/flight.cxx,v
retrieving revision 1.28
diff -u -p -r1.28 flight.cxx
--- flight.cxx 26 Jul 2006 14:18:06 -0000 1.28
+++ flight.cxx 21 Dec 2006 01:04:11 -0000
@@ -870,6 +870,34 @@ FGInterface::get_agl_m(double t, const d
return ret;
}
+bool
+FGInterface::get_agl_m(double t, const double pt[3],
+ double contact[3], double normal[3], double vel[3],
+ int *type, double *loadCapacity,
+ double *frictionFactor, double *agl,
+ double *rollingFritction, double *loadResistance,
+ double *bumpiness, bool *isSolid)
+{
+ const SGMaterial* material;
+ bool ret = ground_cache.get_agl(t, pt, 2.0, contact, normal, vel, type,
+ &material, agl);
+ if (material) {
+ *loadCapacity = material->get_load_resistence();
+ *frictionFactor = material->get_friction_factor();
+ *rollingFritction = material->get_rolling_friction();
+ *loadResistance = material->get_load_resistence();
+ *bumpiness = material->get_bumpiness();
+ *isSolid = material->get_solid();
+ } else {
+ *loadCapacity = DBL_MAX;
+ *frictionFactor = 1.0;
+ *rollingFritction = 0.02;
+ *loadResistance = DBL_MAX;
+ *bumpiness = 0.0;
+ }
+ return ret;
+}
+
// Legacy interface just kept because of JSBSim
bool
FGInterface::get_agl_ft(double t, const double pt[3],
Index: flight.hxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/flight.hxx,v
retrieving revision 1.13
diff -u -p -r1.13 flight.hxx
--- flight.hxx 11 Jun 2006 13:34:19 -0000 1.13
+++ flight.hxx 21 Dec 2006 01:04:16 -0000
@@ -1128,6 +1128,12 @@ public:
double contact[3], double normal[3], double vel[3],
int *type, double *loadCapacity,
double *frictionFactor, double *agl);
+ bool get_agl_m(double t, const double pt[3],
+ double contact[3], double normal[3], double vel[3],
+ int *type, double *loadCapacity,
+ double *frictionFactor, double *agl,
+ double *rollingFritction, double *loadResistance,
+ double *bumpiness,bool *isSolid);
bool get_agl_ft(double t, const double pt[3],
double contact[3], double normal[3], double vel[3],
int *type, double *loadCapacity,
Index: YASim/FGFDM.cpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/FGFDM.cpp,v
retrieving revision 1.44.2.1
diff -u -p -r1.44.2.1 FGFDM.cpp
--- YASim/FGFDM.cpp 18 Dec 2006 21:32:56 -0000 1.44.2.1
+++ YASim/FGFDM.cpp 21 Dec 2006 01:04:32 -0000
@@ -273,6 +273,10 @@ void FGFDM::startElement(const char* nam
g->setDynamicFriction(attrf(a, "dfric", 0.7));
g->setSpring(attrf(a, "spring", 1));
g->setDamping(attrf(a, "damp", 1));
+ if(attrb(a,"only-on-water"))g->setOnlyOnWater(1);
+ if(attrb(a,"not-on-water"))g->setNotOnWater(1);
+ g->setInverseSpeedSpringIsDoubled(attrf(a,
"inverse-speed-spring-is-doubled", 0));
+ g->setReduceFrictionBySpeed(attrf(a, "reduce-friction-by-speed", 0));
_airplane.addGear(g);
} else if(eq(name, "hook")) {
Hook* h = new Hook();
Index: YASim/FGGround.cpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/FGGround.cpp,v
retrieving revision 1.2
diff -u -p -r1.2 FGGround.cpp
--- YASim/FGGround.cpp 18 Feb 2005 12:40:39 -0000 1.2
+++ YASim/FGGround.cpp 21 Dec 2006 01:04:32 -0000
@@ -35,6 +35,29 @@ void FGGround::getGroundPlane(const doub
for(int i=0; i<3; i++) vel[i] = dvel[i];
}
+void FGGround::getGroundPlane(const double pos[3],
+ double plane[4], float vel[3],
+ int *type,
+ double *frictionFactor,
+ double *rollingFriction,
+ double *loadCapacity,
+ double *loadResistance,
+ double *bumpiness,
+ bool *isSolid)
+{
+ // Return values for the callback.
+ double agl;
+ double cp[3], dvel[3];
+ _iface->get_agl_m(_toff, pos, cp, plane, dvel,
+ type, loadCapacity, frictionFactor, &agl,
+ rollingFriction,loadResistance,bumpiness,isSolid);
+
+ // The plane below the actual contact point.
+ plane[3] = plane[0]*cp[0] + plane[1]*cp[1] + plane[2]*cp[2];
+
+ for(int i=0; i<3; i++) vel[i] = dvel[i];
+}
+
bool FGGround::caughtWire(const double pos[4][3])
{
return _iface->caught_wire_m(_toff, pos);
Index: YASim/FGGround.hpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/FGGround.hpp,v
retrieving revision 1.1
diff -u -p -r1.1 FGGround.hpp
--- YASim/FGGround.hpp 17 Feb 2005 10:37:26 -0000 1.1
+++ YASim/FGGround.hpp 21 Dec 2006 01:04:32 -0000
@@ -18,6 +18,16 @@ public:
virtual void getGroundPlane(const double pos[3],
double plane[4], float vel[3]);
+ virtual void FGGround::getGroundPlane(const double pos[3],
+ double plane[4], float vel[3],
+ int *type,
+ double *frictionFactor,
+ double *rollingFriction,
+ double *loadCapacity,
+ double *loadResistance,
+ double *bumpiness,
+ bool *isSolid);
+
virtual bool caughtWire(const double pos[4][3]);
virtual bool getWire(double end[2][3], float vel[2][3]);
Index: YASim/Gear.cpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/Gear.cpp,v
retrieving revision 1.7
diff -u -p -r1.7 Gear.cpp
--- YASim/Gear.cpp 24 Nov 2005 17:35:42 -0000 1.7
+++ YASim/Gear.cpp 21 Dec 2006 01:04:33 -0000
@@ -4,6 +4,9 @@
#include "Gear.hpp"
namespace yasim {
+static const float YASIM_PI = 3.14159265358979323846;
+static const float maxGroundBumpAmplitude=0.5;
+ //Amplitude can be positive and negative
Gear::Gear()
{
@@ -19,6 +22,19 @@ Gear::Gear()
_extension = 1;
_castering = false;
_frac = 0;
+ _ground_type = 0;
+ _ground_frictionFactor = 1;
+ _ground_rollingFriction = 0.02;
+ _ground_loadCapacity = 1e30;
+ _ground_loadResistance = 1e30;
+ _ground_isSolid=1;
+ _ground_bumpiness = 0;
+ _onlyOnWater=0;
+ _notOnWater=1;
+ _global_x=0.0;
+ _global_y=0.0;
+ _inverseSpeedSpringIsDoubled=0;
+ _reduceFrictionBySpeed=0;
for(i=0; i<3; i++)
_global_ground[i] = _global_vel[i] = 0;
@@ -78,11 +94,46 @@ void Gear::setCastering(bool c)
_castering = c;
}
-void Gear::setGlobalGround(double *global_ground, float* global_vel)
+void Gear::setOnlyOnWater(bool c)
+{
+ _onlyOnWater = c;
+}
+
+void Gear::setNotOnWater(bool c)
+{
+ _notOnWater = c;
+}
+
+void Gear::setInverseSpeedSpringIsDoubled(float s)
+{
+ _inverseSpeedSpringIsDoubled=s;
+}
+
+void Gear::setReduceFrictionBySpeed(float s)
+{
+ _reduceFrictionBySpeed=s;
+}
+
+void Gear::setGlobalGround(double *global_ground, float* global_vel,
+ double globalX, double globalY,
+ int type, double frictionFactor,
+ double rollingFriction, double loadCapacity,
+ double loadResistance, double bumpiness,
+ bool isSolid)
{
int i;
for(i=0; i<4; i++) _global_ground[i] = global_ground[i];
for(i=0; i<3; i++) _global_vel[i] = global_vel[i];
+ _ground_type = type;
+ _ground_frictionFactor=frictionFactor;
+ _ground_rollingFriction=rollingFriction;
+ _ground_loadCapacity=loadCapacity;
+ _ground_loadResistance=loadResistance;
+ _ground_bumpiness=bumpiness;
+ _ground_isSolid=isSolid;
+ _global_x=globalX;
+ _global_y=globalY;
+
}
void Gear::getPosition(float* out)
@@ -159,6 +210,26 @@ bool Gear::getCastering()
return _castering;
}
+float Gear::getBumbAltitude()
+{
+ if (_ground_bumpiness<0.001) return 0.0;
+ double x = _global_x*10;
+ double y = _global_y*10;
+ x-=Math::floor(x);
+ y-=Math::floor(y);
+ x*=2*YASIM_PI;
+ y*=2*YASIM_PI;
+ //now x and y are in the range of 0..2pi
+ //we need a function, that is periodically on 2pi and gives some
+ //height. This is not very fast, but for a beginning.
+ //maybe this should be done by interpolating between some precalculated
+ //values
+ float h= Math::sin(x)+Math::sin(7*x)+Math::sin(8*x)+Math::sin(13*x);
+ h+= Math::sin(2*y)+Math::sin(5*y)+Math::sin(9*y*x)+Math::sin(17*y);
+
+ return h *(1/8.)*_ground_bumpiness*maxGroundBumpAmplitude;
+}
+
void Gear::calcForce(RigidBody* body, State *s, float* v, float* rot)
{
// Init the return values
@@ -169,6 +240,15 @@ void Gear::calcForce(RigidBody* body, St
if(_extension < 1)
return;
+ if ((_onlyOnWater&&_ground_isSolid)||(_notOnWater&&!_ground_isSolid)) {
+ _wow = 0;
+ _frac = 0;
+ _compressDist = 0;
+ _rollSpeed = 0;
+ _casterAngle = 0;
+ return;
+ }
+
// The ground plane transformed to the local frame.
float ground[4];
s->planeGlobalToLocal(_global_ground, ground);
@@ -180,6 +260,12 @@ void Gear::calcForce(RigidBody* body, St
// First off, make sure that the gear "tip" is below the ground.
// If it's not, there's no force.
float a = ground[3] - Math::dot3(_pos, ground);
+ float BumbAltitude=0;
+ if (a<maxGroundBumpAmplitude)
+ {
+ BumbAltitude=getBumbAltitude();
+ a+=BumbAltitude;
+ }
_compressDist = -a;
if(a > 0) {
_wow = 0;
@@ -196,7 +282,7 @@ void Gear::calcForce(RigidBody* body, St
// above ground is negative.
float tmp[3];
Math::add3(_cmpr, _pos, tmp);
- float b = ground[3] - Math::dot3(tmp, ground);
+ float b = ground[3] - Math::dot3(tmp, ground)+BumbAltitude;
// Calculate the point of ground _contact.
_frac = a/(a-b);
@@ -219,7 +305,11 @@ void Gear::calcForce(RigidBody* body, St
// compression. (note the clamping of _frac to 1):
_frac = (_frac > 1) ? 1 : _frac;
float fmag = _frac*clen*_spring;
-
+ float inversespeed_multiplied_by_speed=0;
+ if (_inverseSpeedSpringIsDoubled>0.0000001) {
+
inversespeed_multiplied_by_speed=Math::mag3(cv)*_inverseSpeedSpringIsDoubled;
+ fmag*=1+inversespeed_multiplied_by_speed;
+ }
// Then the damping. Use the only the velocity into the ground
// (projection along "ground") projected along the compression
// axis. So Vdamp = ground*(ground dot cv) dot cmpr
@@ -285,10 +375,18 @@ void Gear::calcForce(RigidBody* body, St
_casterAngle = _rot;
}
- float fsteer = _brake * calcFriction(wgt, vsteer);
- float fskid = calcFriction(wgt, vskid);
+ float fsteer = (_brake * _ground_frictionFactor
+ +(1-_brake)*_ground_rollingFriction
+ )*calcFriction(wgt, vsteer);
+ float fskid = calcFriction(wgt, vskid)*_ground_frictionFactor;
if(vsteer > 0) fsteer = -fsteer;
if(vskid > 0) fskid = -fskid;
+
+ //reduce friction if wanted by _reduceFrictionBySpeed
+ float factor = 1-inversespeed_multiplied_by_speed*_reduceFrictionBySpeed;
+ factor=Math::clamp(factor,0,1);
+ fsteer*=factor;
+ fskid*=factor;
// Phoo! All done. Add it up and get out of here.
Math::mul3(fsteer, steer, tmp);
Index: YASim/Gear.hpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/Gear.hpp,v
retrieving revision 1.5
diff -u -p -r1.5 Gear.hpp
--- YASim/Gear.hpp 24 Nov 2005 17:35:42 -0000 1.5
+++ YASim/Gear.hpp 21 Dec 2006 01:04:33 -0000
@@ -39,8 +39,15 @@ public:
void setRotation(float rotation);
void setExtension(float extension);
void setCastering(bool castering);
- void setGlobalGround(double* global_ground, float* global_vel);
-
+ void setOnlyOnWater(bool c);
+ void setNotOnWater(bool c);
+ void setInverseSpeedSpringIsDoubled(float s);
+ void setReduceFrictionBySpeed(float s);
+ void setGlobalGround(double* global_ground, float* global_vel,
+ double globalX, double globalY,
+ int type, double frictionFactor,double rollingFriction,
+ double loadCapacity, double loadResistance, double bumpiness,
+ bool isSolid);
void getPosition(float* out);
void getCompression(float* out);
void getGlobalGround(double* global_ground);
@@ -54,6 +61,8 @@ public:
bool getCastering();
float getCasterAngle() { return _casterAngle; }
float getRollSpeed() { return _rollSpeed; }
+ float getBumbAltitude();
+
// Takes a velocity of the aircraft relative to ground, a rotation
// vector, and a ground plane (all specified in local coordinates)
@@ -90,6 +99,19 @@ private:
float _global_vel[3];
float _casterAngle;
float _rollSpeed;
+ int _ground_type;
+ double _ground_frictionFactor;
+ double _ground_rollingFriction;
+ double _ground_loadCapacity;
+ double _ground_loadResistance;
+ double _ground_bumpiness;
+ bool _ground_isSolid;
+ bool _onlyOnWater;
+ bool _notOnWater;
+ float _inverseSpeedSpringIsDoubled;
+ float _reduceFrictionBySpeed;
+ double _global_x;
+ double _global_y;
};
}; // namespace yasim
Index: YASim/Ground.cpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/Ground.cpp,v
retrieving revision 1.1
diff -u -p -r1.1 Ground.cpp
--- YASim/Ground.cpp 17 Feb 2005 10:37:26 -0000 1.1
+++ YASim/Ground.cpp 21 Dec 2006 01:04:34 -0000
@@ -28,6 +28,19 @@ void Ground::getGroundPlane(const double
vel[2] = 0.0;
}
+void Ground::getGroundPlane(const double pos[3],
+ double plane[4], float vel[3],
+ int *type,
+ double *frictionFactor,
+ double *rollingFriction,
+ double *loadCapacity,
+ double *loadResistance,
+ double *bumpiness,
+ bool *isSolid)
+{
+ getGroundPlane(pos,plane,vel);
+}
+
bool Ground::caughtWire(const double pos[4][3])
{
return false;
Index: YASim/Ground.hpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/Ground.hpp,v
retrieving revision 1.1
diff -u -p -r1.1 Ground.hpp
--- YASim/Ground.hpp 17 Feb 2005 10:37:26 -0000 1.1
+++ YASim/Ground.hpp 21 Dec 2006 01:04:34 -0000
@@ -11,6 +11,16 @@ public:
virtual void getGroundPlane(const double pos[3],
double plane[4], float vel[3]);
+ virtual void getGroundPlane(const double pos[3],
+ double plane[4], float vel[3],
+ int *type,
+ double *frictionFactor,
+ double *rollingFriction,
+ double *loadCapacity,
+ double *loadResistance,
+ double *bumpiness,
+ bool *isSolid);
+
virtual bool caughtWire(const double pos[4][3]);
virtual bool getWire(double end[2][3], float vel[2][3]);
Index: YASim/Model.cpp
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/FDM/YASim/Model.cpp,v
retrieving revision 1.13
diff -u -p -r1.13 Model.cpp
--- YASim/Model.cpp 14 Sep 2006 18:18:33 -0000 1.13
+++ YASim/Model.cpp 21 Dec 2006 01:04:36 -0000
@@ -307,8 +307,26 @@ void Model::updateGround(State* s)
// Ask for the ground plane in the global coordinate system
double global_ground[4];
float global_vel[3];
- _ground_cb->getGroundPlane(pt, global_ground, global_vel);
- g->setGlobalGround(global_ground, global_vel);
+ int type;
+ double frictionFactor, rollingFriction, loadCapacity,
+ loadResistance, bumpiness;
+ bool isSolid;
+ //_ground_cb->getGroundPlane(pt, global_ground, global_vel);
+ _ground_cb->getGroundPlane(pt, global_ground, global_vel,
+ &type,&frictionFactor, &rollingFriction,
+ &loadCapacity,
&loadResistance,&bumpiness,&isSolid);
+ static int h=0;
+ /*
+ if (h++>100)
+ {
+ cout<<"t:"<<type<<"fF:"<<frictionFactor<<"rF:"<<rollingFriction
+ <<"lC:"<<loadCapacity<<"lR"<<loadResistance<<"b:"<<bumpiness<<"
\r";
+ h=0;
+ }
+ */
+ g->setGlobalGround(global_ground, global_vel, pt[0], pt[1],type,
+ frictionFactor, rollingFriction, loadCapacity, loadResistance,
+ bumpiness,isSolid);
}
for(i=0; i<_rotorgear.getRotors()->size(); i++) {
Rotor* r = (Rotor*)_rotorgear.getRotors()->get(i);
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