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Attenuate turbulence near the ground. Tweak turbulence numbers.

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andy 2004-01-12 04:03:55 +00:00
parent 492d5fbd8d
commit ba44655796
4 changed files with 44 additions and 23 deletions
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44
src/FDM/YASim/Model.cpp
View file

@ -79,13 +79,18 @@ void Model::initIteration()
int i;
for(i=0; i<3; i++)
_gyro[i] = _torque[i] = 0;
// Need a local altitude for the wind calculation
float dummy[3];
float alt = Math::abs(localGround(_s, dummy));
for(i=0; i<_thrusters.size(); i++) {
Thruster* t = (Thruster*)_thrusters.get(i);
// Get the wind velocity at the thruster location
float pos[3], v[3];
t->getPosition(pos);
localWind(pos, _s, v);
localWind(pos, _s, v, alt);
t->setWind(v);
t->setAir(_pressure, _temp, _rho);
@ -251,8 +256,7 @@ void Model::setGroundEffect(float* pos, float span, float mul)
// (v dot _ground)-_ground[3] gives the distance AGL.
void Model::setGroundPlane(double* planeNormal, double fromOrigin)
{
int i;
for(i=0; i<3; i++) _ground[i] = planeNormal[i];
for(int i=0; i<3; i++) _ground[i] = planeNormal[i];
_ground[3] = fromOrigin;
}
@ -286,6 +290,14 @@ void Model::calcForces(State* s)
_body.addForce(pos, thrust);
}
// Get a ground plane in local coordinates. The first three
// elements are the normal vector, the final one is the distance
// from the local origin along that vector to the ground plane
// (negative for objects "above" the ground)
float ground[4];
ground[3] = localGround(s, ground);
float alt = Math::abs(ground[3]);
// Gravity, convert to a force, then to local coordinates
float grav[3];
Glue::geodUp(s->pos, grav);
@ -303,7 +315,7 @@ void Model::calcForces(State* s)
// Vsurf = wind - velocity + (rot cross (cg - pos))
float vs[3], pos[3];
sf->getPosition(pos);
localWind(pos, s, vs);
localWind(pos, s, vs, alt);
float force[3], torque[3];
sf->calcForce(vs, _rho, force, torque);
@ -318,7 +330,7 @@ void Model::calcForces(State* s)
// Vsurf = wind - velocity + (rot cross (cg - pos))
float vs[3], pos[3];
sf->getPosition(pos);
localWind(pos, s, vs);
localWind(pos, s, vs, alt);
float force[3], torque[3];
sf->calcForce(vs, _rho, force, torque);
@ -335,7 +347,7 @@ void Model::calcForces(State* s)
// Vsurf = wind - velocity + (rot cross (cg - pos))
float vs[3], pos[3];
sf->getPosition(pos);
localWind(pos, s, vs);
localWind(pos, s, vs, alt);
float force[3], torque[3];
sf->calcForce(vs, _rho, force, torque);
@ -347,13 +359,6 @@ void Model::calcForces(State* s)
_body.addTorque(torque);
}
// Get a ground plane in local coordinates. The first three
// elements are the normal vector, the final one is the distance
// from the local origin along that vector to the ground plane
// (negative for objects "above" the ground)
float ground[4];
ground[3] = localGround(s, ground);
// Account for ground effect by multiplying the vertical force
// component by an amount linear with the fraction of the wingspan
// above the ground.
@ -433,19 +438,20 @@ float Model::localGround(State* s, float* out)
// Calculates the airflow direction at the given point and for the
// specified aircraft velocity.
void Model::localWind(float* pos, State* s, float* out)
void Model::localWind(float* pos, State* s, float* out, float alt)
{
float tmp[3], lwind[3], lrot[3], lv[3];
// Get a global coordinate for our local position, and calculate
// turbulence.
// FIXME: modify turbulence for altitude, attenuating the vertical
// component near the ground.
if(_turb) {
double gpos[3];
double gpos[3]; float up[3];
Math::tmul33(s->orient, pos, tmp);
for(int i=0; i<3; i++) gpos[i] = s->pos[i] + tmp[i];
_turb->getTurbulence(gpos, lwind);
for(int i=0; i<3; i++) {
gpos[i] = s->pos[i] + tmp[i];
up[i] = _ground[i];
}
_turb->getTurbulence(gpos, alt, up, lwind);
Math::add3(_wind, lwind, lwind);
} else {
Math::set3(_wind, lwind);

2
src/FDM/YASim/Model.hpp
View file

@ -74,7 +74,7 @@ private:
void calcGearForce(Gear* g, float* v, float* rot, float* ground);
float gearFriction(float wgt, float v, Gear* g);
float localGround(State* s, float* out);
void localWind(float* pos, State* s, float* out);
void localWind(float* pos, State* s, float* out, float alt);
Integrator _integrator;
RigidBody _body;

19
src/FDM/YASim/Turbulence.cpp
View file

@ -25,7 +25,7 @@ const double MAGNITUDE_EXP = 2.0;
// bandwidth to the higher frequency components. A turbulence field
// will swing between maximal values over a distance of approximately
// 2^(MEANINGFUL_GENS-1).
const int MEANINGFUL_GENS = 8;
const int MEANINGFUL_GENS = 7;
static const float FT2M = 0.3048;
@ -130,7 +130,8 @@ void Turbulence::offset(float* offset)
_off[i] += offset[i];
}
void Turbulence::getTurbulence(double* loc, float* turbOut)
void Turbulence::getTurbulence(double* loc, float alt, float* up,
float* turbOut)
{
// Convert to integer 2D coordinates; wrap to [0:_sz].
double a = (loc[0] + _off[0]) + (loc[2] + _off[2]);
@ -158,6 +159,20 @@ void Turbulence::getTurbulence(double* loc, float* turbOut)
float avg1 = (1-a)*turb10[i] + a*turb11[i];
turbOut[i] = mag * ((1-b)*avg0 + b*avg1);
}
// Adjust for altitude effects
if(alt < 300) {
float altmul = 0.5 + (1-0.5) * (alt*(1.0/300));
if(alt < 100) {
float vmul = alt * (1.0/100);
vmul = vmul / altmul; // pre-correct for the pending altmul
float dot = Math::dot3(turbOut, up);
float off[3];
Math::mul3(dot * (vmul-1), up, off);
Math::add3(turbOut, off, turbOut);
}
Math::mul3(altmul, turbOut, turbOut);
}
}
// Associates a random number in the range [-1:1] with a given lattice

2
src/FDM/YASim/Turbulence.hpp
View file

@ -6,7 +6,7 @@ public:
~Turbulence();
void update(double dt, double rate);
void setMagnitude(double mag);
void getTurbulence(double* loc, float* turbOut);
void getTurbulence(double* loc, float alt, float* up, float* turbOut);
void offset(float* dist);
private: