#include "Math.hpp"
+#include "BodyEnvironment.hpp"
#include "RigidBody.hpp"
#include "Gear.hpp"
Gear::Gear()
{
- for(int i=0; i<3; i++)
+ int i;
+ for(i=0; i<3; i++)
_pos[i] = _cmpr[i] = 0;
_spring = 1;
_damp = 0;
- _sfric = 0.8;
- _dfric = 0.7;
+ _sfric = 0.8f;
+ _dfric = 0.7f;
_brake = 0;
_rot = 0;
_extension = 1;
+ _castering = false;
+ _frac = 0;
+
+ for(i=0; i<3; i++)
+ _global_ground[i] = _global_vel[i] = 0;
+ _global_ground[2] = 1;
+ _global_ground[3] = -1e3;
}
void Gear::setPosition(float* position)
{
- for(int i=0; i<3; i++) _pos[i] = position[i];
+ int i;
+ for(i=0; i<3; i++) _pos[i] = position[i];
}
void Gear::setCompression(float* compression)
{
- for(int i=0; i<3; i++) _cmpr[i] = compression[i];
+ int i;
+ for(i=0; i<3; i++) _cmpr[i] = compression[i];
}
void Gear::setSpring(float spring)
void Gear::setBrake(float brake)
{
- _brake = brake;
+ _brake = Math::clamp(brake, 0, 1);
}
void Gear::setRotation(float rotation)
void Gear::setExtension(float extension)
{
- _extension = extension;
+ _extension = Math::clamp(extension, 0, 1);
+}
+
+void Gear::setCastering(bool c)
+{
+ _castering = c;
+}
+
+void Gear::setGlobalGround(double *global_ground, float* global_vel)
+{
+ 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];
}
void Gear::getPosition(float* out)
{
- for(int i=0; i<3; i++) out[i] = _pos[i];
+ int i;
+ for(i=0; i<3; i++) out[i] = _pos[i];
}
void Gear::getCompression(float* out)
{
- for(int i=0; i<3; i++) out[i] = _cmpr[i];
+ int i;
+ for(i=0; i<3; i++) out[i] = _cmpr[i];
+}
+
+void Gear::getGlobalGround(double* global_ground)
+{
+ int i;
+ for(i=0; i<4; i++) global_ground[i] = _global_ground[i];
}
float Gear::getSpring()
return _frac;
}
-void Gear::calcForce(RigidBody* body, float* v, float* rot, float* ground)
+bool Gear::getCastering()
+{
+ return _castering;
+}
+
+void Gear::calcForce(RigidBody* body, State *s, float* v, float* rot)
{
// Init the return values
- for(int i=0; i<3; i++) _force[i] = _contact[i] = 0;
+ int i;
+ for(i=0; i<3; i++) _force[i] = _contact[i] = 0;
// Don't bother if it's not down
if(_extension < 1)
return;
- float tmp[3];
+ // The ground plane transformed to the local frame.
+ float ground[4];
+ s->planeGlobalToLocal(_global_ground, ground);
+
+ // The velocity of the contact patch transformed to local coordinates.
+ float glvel[3];
+ s->velGlobalToLocal(_global_vel, glvel);
// 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);
- if(a > 0)
+ _compressDist = -a;
+ if(a > 0) {
+ _wow = 0;
+ _frac = 0;
+ _compressDist = 0;
+ _rollSpeed = 0;
+ _casterAngle = 0;
return;
+ }
// Now a is the distance from the tip to ground, so make b the
// distance from the base to ground. We can get the fraction
// (0-1) of compression from a/(a-b). Note the minus sign -- stuff
// above ground is negative.
+ float tmp[3];
Math::add3(_cmpr, _pos, tmp);
float b = ground[3] - Math::dot3(tmp, ground);
// Calculate the point of ground _contact.
_frac = a/(a-b);
if(b < 0) _frac = 1;
- for(int i=0; i<3; i++)
+ for(i=0; i<3; i++)
_contact[i] = _pos[i] + _frac*_cmpr[i];
// Turn _cmpr into a unit vector and a magnitude
float cv[3];
body->pointVelocity(_contact, rot, cv);
Math::add3(cv, v, cv);
+ Math::sub3(cv, glvel, cv);
- // Finally, we can start adding up the forces. First the
- // spring compression (note the clamping of _frac to 1):
+ // Finally, we can start adding up the forces. First the spring
+ // compression. (note the clamping of _frac to 1):
_frac = (_frac > 1) ? 1 : _frac;
float fmag = _frac*clen*_spring;
- Math::mul3(fmag, cmpr, _force);
// Then the damping. Use the only the velocity into the ground
// (projection along "ground") projected along the compression
float damp = _damp * dv;
if(damp > fmag) damp = fmag; // can't pull the plane down!
if(damp < -fmag) damp = -fmag; // sanity
- Math::mul3(-damp, cmpr, tmp);
- Math::add3(_force, tmp, _force);
- _wow = fmag - damp;
+ // The actual force applied is only the component perpendicular to
+ // the ground. Side forces come from velocity only.
+ _wow = (fmag - damp) * -Math::dot3(cmpr, ground);
+ Math::mul3(-_wow, ground, _force);
// Wheels are funky. Split the velocity along the ground plane
// into rolling and skidding components. Assuming small angles,
Math::cross3(skid, gup, steer); // skid cross up == steer
if(_rot != 0) {
- // Correct for a (small) rotation
- Math::mul3(_rot, steer, tmp);
- Math::add3(tmp, skid, skid);
- Math::unit3(skid, skid);
- Math::cross3(skid, gup, steer);
+ // Correct for a rotation
+ float srot = Math::sin(_rot);
+ float crot = Math::cos(_rot);
+ float tx = steer[0];
+ float ty = steer[1];
+ steer[0] = crot*tx + srot*ty;
+ steer[1] = -srot*tx + crot*ty;
+
+ tx = skid[0];
+ ty = skid[1];
+ skid[0] = crot*tx + srot*ty;
+ skid[1] = -srot*tx + crot*ty;
}
float vsteer = Math::dot3(cv, steer);
float vskid = Math::dot3(cv, skid);
float wgt = Math::dot3(_force, gup); // force into the ground
+ if(_castering) {
+ _rollSpeed = Math::sqrt(vsteer*vsteer + vskid*vskid);
+ // Don't modify caster angle when the wheel isn't moving,
+ // or else the angle will animate the "jitter" of a stopped
+ // gear.
+ if(_rollSpeed > 0.05)
+ _casterAngle = Math::atan2(vskid, vsteer);
+ return;
+ } else {
+ _rollSpeed = vsteer;
+ _casterAngle = _rot;
+ }
+
float fsteer = _brake * calcFriction(wgt, vsteer);
float fskid = calcFriction(wgt, vskid);
if(vsteer > 0) fsteer = -fsteer;
float Gear::calcFriction(float wgt, float v)
{
- // How slow is stopped? 50 cm/second?
- const float STOP = 0.5;
- const float iSTOP = 1/STOP;
+ // How slow is stopped? 10 cm/second?
+ const float STOP = 0.1f;
+ const float iSTOP = 1.0f/STOP;
v = Math::abs(v);
if(v < STOP) return v*iSTOP * wgt * _sfric;
else return wgt * _dfric;
projects / flightgear.git / blobdiff