posit.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2018, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

#include "vision-precomp.h"  // Precompiled headers
#include <iostream>
#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 "posit.h"

mrpt::vision::pnp::posit::posit(
    Eigen::MatrixXd obj_pts_, Eigen::MatrixXd img_pts_,
    Eigen::MatrixXd camera_intrinsic_, int n0)
{
    obj_pts = obj_pts_;
    img_pts = img_pts_.block(0, 0, n0, 2);
    cam_intrinsic = camera_intrinsic_;
    R = Eigen::MatrixXd::Identity(3, 3);
    t = Eigen::VectorXd::Zero(3);
    f = (cam_intrinsic(0, 0) + cam_intrinsic(1, 1)) / 2;

    obj_matrix =
        (obj_pts.transpose() * obj_pts).inverse() * obj_pts.transpose();

    n = n0;

    obj_vecs = Eigen::MatrixXd::Zero(n0, 3);

    for (int i = 0; i < n; i++)
        obj_vecs.row(i) = obj_pts.row(i) - obj_pts.row(0);

    img_vecs = Eigen::MatrixXd::Zero(n0, 2);
    img_vecs_old = img_vecs;

    epsilons = Eigen::VectorXd::Zero(n);
}

void mrpt::vision::pnp::posit::POS()
{
    Eigen::Vector3d I0, J0, r1, r2, r3;
    double I0_norm, J0_norm;

    int i;
    double scale;

    for (i = 0; i < 3; i++)
    {
        I0(i) = obj_matrix.row(i).dot(img_vecs.col(0));
        J0(i) = obj_matrix.row(i).dot(img_vecs.col(1));
    }

    I0_norm = I0.norm();
    J0_norm = J0.norm();

    scale = (I0_norm + J0_norm) / 2;

    /*Computing TRANSLATION */
    t(0) = img_pts(0, 0) / scale;
    t(1) = img_pts(0, 1) / scale;
    t(2) = f / scale;

    /* Computing ROTATION */
    r1 = I0 / I0_norm;
    r2 = J0 / J0_norm;
    r3 = r1.cross(r2);

    R.row(0) = r1;
    R.row(1) = r2;
    R.row(2) = r3;
}

/**
Iterate over results obtained by the POS function;
see paper "Model-Based Object Pose in 25 Lines of Code", IJCV 15, pp. 123-141,
1995.
*/
bool mrpt::vision::pnp::posit::compute_pose(
    Eigen::Ref<Eigen::Matrix3d> R_, Eigen::Ref<Eigen::Vector3d> t_)
{
    Eigen::FullPivLU<Eigen::MatrixXd> lu(obj_pts);
    if (lu.rank() < 3) return false;

    int i, iCount;
    long imageDiff = 1000;

    for (iCount = 0; iCount < LOOP_MAX_COUNT; iCount++)
    {
        if (iCount == 0)
        {
            for (i = 0; i < img_vecs.rows(); i++)
                img_vecs.row(i) = img_pts.row(i) - img_pts.row(0);
        }

        else
        {
            // Compute new image vectors
            epsilons.setZero();
            for (i = 0; i < n; i++)
            {
                epsilons(i) += obj_vecs.row(i).dot(R.row(2));
            }
            epsilons /= t(2);

            // Corrected image vectors
            for (i = 0; i < n; i++)
            {
                img_vecs.row(i) =
                    img_pts.row(i) * (1 + epsilons(i)) - img_pts.row(0);
            }

            imageDiff = this->get_img_diff();
        }

        img_vecs_old = img_vecs;

        this->POS();

        if (iCount > 0 && imageDiff == 0) break;

        if (iCount == LOOP_MAX_COUNT)
        {
            std::cout << "Solution Not converged" << std::endl << std::endl;
            break;
        }
    }
    R_ = R;
    t_ = t;

    return true;
}

long mrpt::vision::pnp::posit::get_img_diff()
{
    int i, j;
    long sumOfDiffs = 0;

    for (i = 0; i < n; i++)
    {
        for (j = 0; j < 2; j++)
        {
            sumOfDiffs += std::abs(
                floor(0.5 + img_vecs(i, j)) - floor(0.5 + img_vecs_old(i, j)));
        }
    }
    return sumOfDiffs;
}