void PhysicsVehicleWheel::transform(Node* node) const
{
GP_ASSERT(_host);
GP_ASSERT(_host->_node);
node->setRotation(_orientation);
// Use only the component parallel to the defined strut line
Vector3 strutLine;
getWheelDirection(&strutLine);
_host->_node->getMatrix().transformVector(&strutLine);
Vector3 wheelPos;
getWheelPos(&wheelPos);
node->setTranslation(wheelPos + strutLine*(strutLine.dot(_positionDelta) / strutLine.lengthSquared()));
}
void PhysicsVehicleWheel::getConnectionDefault(Vector3* result) const
{
// projected strut length
getWheelDirection(result);
result->normalize();
float length = 0.58f * getStrutRestLength();
*result *= -length;
// nudge wheel contact point to outer edge of tire for stability
Vector3 nudge;
getWheelAxle(&nudge);
nudge *= nudge.dot(_initialOffset);
nudge.normalize();
*result += nudge * 0.068f * getWheelRadius(); // rough-in for tire width
// offset at bind time
*result += _initialOffset;
}
void Wheel::calculateForces(double dt)
{
f = Vector2D(0, 0);
force_moment = 0;
double mu_par, mu_perp;
switch (state)
{
case WheelState::Broken:
mu_par = mu_broken_friction;
mu_perp = mu_broken_friction;
break;
case WheelState::Braking:
mu_par = mu_parallel_friction;
mu_perp = mu_perpendicular_friction;
break;
case WheelState::Free:
case WheelState::Forward:
case WheelState::Backward:
default:
mu_par = mu_parallel_roll / radius;
mu_perp = mu_perpendicular_friction;
break;
}
double vl = v.getLength();
Vector2D w = getWheelDirection();
double v_par = std::abs(v.scalar(w));
double v_perp = sqrt(std::abs(vl * vl - v_par * v_par));
if (v_par > eps) {
Vector2D f_par = w;
if (f_par.scalar(v) > 0)
{
f_par.mul(-1);
}
f_par.mul(distributed_weight * getChangedMu(mu_par));
if (f_par.getLength() > shaking_koef * v_par * (distributed_weight / G) / dt)
{
f_par.setLength(shaking_koef * v_par * (distributed_weight / G) / dt);
}/**/
f.add(f_par);
}
if (v_perp > eps) {
Vector2D f_perp = w;
f_perp.rotate(M_PI / 2);
if (f_perp.scalar(v) > 0)
{
f_perp.mul(-1);
}
f_perp.mul(distributed_weight * getChangedMu(mu_perp));
if (f_perp.getLength() > shaking_koef * v_perp * (distributed_weight / G) / dt)
{
f_perp.setLength(shaking_koef * v_perp * (distributed_weight / G) / dt);
}/**/
force_moment += 10 * r.cross(f_perp);
Vector2D p_f_p(f_perp.getLength(), 0);
if (p_f_p.scalar(v) > 0)
{
p_f_p.mul(-1);
}
double p_v_perp = std::abs(v.scalar(Vector2D(1, 0)));
if (p_f_p.getLength() > shaking_koef * p_v_perp * (distributed_weight / G) / dt)
{
p_f_p.setLength(shaking_koef * p_v_perp * (distributed_weight / G) / dt);
}
f.add(p_f_p);
}
if ((state == WheelState::Forward) || (state == WheelState::Backward))
{
int force_koef = (state == WheelState::Forward ? 1 : -1);
Vector2D acc_force = w;
acc_force.mul((force_koef * distributed_torque / radius));
f.add(acc_force);
}
force_moment += r.cross(f);
}
