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Numerically stable refactoring of fisheye jacobian

release/4.3a0
roderick-koehle 2021-10-28 11:56:42 +02:00 committed by GitHub
parent 91103d5f47
commit c0219c1ad0
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1 changed files with 24 additions and 12 deletions
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36
gtsam/geometry/Cal3Fisheye.cpp
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@ -46,7 +46,7 @@ double Cal3Fisheye::Scaling(double r) {
/* ************************************************************************* */
Point2 Cal3Fisheye::uncalibrate(const Point2& p, OptionalJacobian<2, 9> H1,
OptionalJacobian<2, 2> H2) const {
const double xi = p.x(), yi = p.y();
const double xi = p.x(), yi = p.y(), zi = 1;
const double r2 = xi * xi + yi * yi, r = sqrt(r2);
const double t = atan(r);
const double t2 = t * t, t4 = t2 * t2, t6 = t2 * t4, t8 = t4 * t4;
@ -81,21 +81,33 @@ Point2 Cal3Fisheye::uncalibrate(const Point2& p, OptionalJacobian<2, 9> H1,
} else {
const double dtd_dt =
1 + 3 * k1_ * t2 + 5 * k2_ * t4 + 7 * k3_ * t6 + 9 * k4_ * t8;
const double dt_dr = 1 / (1 + r2);
const double R2 = r2 + zi*zi
const double dt_dr = zi / R2;
const double rinv = 1 / r;
const double dr_dxi = xi * rinv;
const double dr_dyi = yi * rinv;
const double dtd_dxi = dtd_dt * dt_dr * dr_dxi;
const double dtd_dyi = dtd_dt * dt_dr * dr_dyi;
const double dtd_dr = dtd_dt * dt_dr
// const double dtd_dxi = dtd_dt * dt_dr * dr_dxi;
// const double dtd_dyi = dtd_dt * dt_dr * dr_dyi;
const double td = t * K.dot(T);
const double rrinv = 1 / r2;
const double dxd_dxi =
dtd_dxi * dr_dxi + td * rinv - td * xi * rrinv * dr_dxi;
const double dxd_dyi = dtd_dyi * dr_dxi - td * xi * rrinv * dr_dyi;
const double dyd_dxi = dtd_dxi * dr_dyi - td * yi * rrinv * dr_dxi;
const double dyd_dyi =
dtd_dyi * dr_dyi + td * rinv - td * yi * rrinv * dr_dyi;
const double c2 = dr_dxi * dr_dxi
const double s2 = dr_dyi * dr_dyi
const double cs = dr_dxi * dr_dyi
// Following refactoring is numerically stable, even for unnormalized radial
// values by avoiding division with the square radius.
//
// const double td = t * K.dot(T); - note: s = td/r
// const double rrinv = 1 / r2; - division by r2 may cause overflow
const double dxd_dxi = dtd_dr * c2 + s * (1 - c2);
const double dxd_dyi = (dtd_dr - s) * cs;
const double dyd_dxi = dxd_dyi;
const double dyd_dyi = dtd_dr * c2 + s * (1 - s2);
// Derivatives by depth, for future use to support incident
// angles above 90 deg.
// const double dxd_dzi = -dtd_dt * x / R2
// const double dyd_dzi = -dtd_dt * y / R2
Matrix2 DR;
DR << dxd_dxi, dxd_dyi, dyd_dxi, dyd_dyi;