/*! Return the angular velocity at the specified time (TDB). The default
* implementation computes the angular velocity via differentiation.
*/
Vector3d
RotationModel::angularVelocityAtTime(double tdb) const
{
double dt = chooseDiffTimeDelta(*this);
Quaterniond q0 = orientationAtTime(tdb);
Quaterniond q1 = orientationAtTime(tdb + dt);
Quaterniond dq = q1.conjugate() * q0;
if (std::abs(dq.w()) > 0.99999999)
return Vector3d::Zero();
return dq.vec().normalized() * (2.0 * acos(dq.w()) / dt);
#ifdef CELVEC
Vector3d v(dq.x, dq.y, dq.z);
v.normalize();
return v * (2.0 * acos(dq.w) / dt);
#endif
}
Vector3d
CachingRotationModel::computeAngularVelocity(double tjd) const
{
double dt = chooseDiffTimeDelta(*this);
Quaterniond q0 = orientationAtTime(tjd);
// Call computeSpin/computeEquatorOrientation instead of orientationAtTime
// in order to avoid affecting the cache.
Quaterniond spin = computeSpin(tjd + dt);
Quaterniond equator = computeEquatorOrientation(tjd + dt);
Quaterniond q1 = spin * equator;
Quaterniond dq = q1.conjugate() * q0;
if (std::abs(dq.w()) > 0.99999999)
return Vector3d::Zero();
return dq.vec().normalized() * (2.0 * acos(dq.w()) / dt);
#ifdef CELVEC
Vec3d v(dq.x, dq.y, dq.z);
v.normalize();
return v * (2.0 * acos(dq.w) / dt);
#endif
}