ppnp.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include "vision-precomp.h"  // Precompiled headers

//#include <mrpt/math/types_math.h>  // Eigen must be included first via MRPT to
// enable the plugin system
#include <Eigen/Dense>
#include <Eigen/SVD>
#include <iostream>

#include "ppnp.h"

mrpt::vision::pnp::ppnp::ppnp(
    const Eigen::MatrixXd& obj_pts, const Eigen::MatrixXd& img_pts,
    const Eigen::MatrixXd& cam_intrinsic)
{
    P = img_pts;
    S = obj_pts;
    C = cam_intrinsic;
}

bool mrpt::vision::pnp::ppnp::compute_pose(
    Eigen::Matrix3d& R, Eigen::Vector3d& t, int n)
{
    double tol = 0.00001;

    Eigen::MatrixXd I = Eigen::MatrixXd::Identity(n, n), A(n, n), Y(n, 3),
                    E(n, 3), E_old(n, 3), U, V,
                    I3 = Eigen::MatrixXd::Identity(3, 3), PR,
                    Z = Eigen::MatrixXd::Zero(n, n);
    Eigen::VectorXd e(n), II(n), c(3), Zmindiag(n);

    e.fill(1);
    II.fill(1.0 / ((double)n));

    A = I - e * e.transpose() / n;

    double err = std::numeric_limits<double>::infinity();

    E_old.fill(1000);

    int cnt = 0;

    while (err > tol)
    {
        Eigen::JacobiSVD<Eigen::MatrixXd> svd(
            P.transpose() * Z * A * S,
            Eigen::ComputeThinU | Eigen::ComputeThinV);
        U = svd.matrixU();
        V = svd.matrixV();

        I3(2, 2) = (U * V.transpose()).determinant();
        R = U * I3 * V.transpose();
        PR = P * R;

        c = (S - Z * PR).transpose() * II;

        Y = S - e * c.transpose();

        Zmindiag = ((PR * Y.transpose()).diagonal()).array() /
                   ((P.array() * P.array()).rowwise().sum()).array();

        for (int i = 0; i < n; i++)
            if (Zmindiag(i) < 0) Zmindiag(i) = 0;

        Z = Zmindiag.asDiagonal();

        E = Y - Z * PR;

        err = (E - E_old).norm();

        E_old = E;

        cnt++;
    }

    t = -R * c;

    return true;
}