CGridMapAligner.h

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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          |
   +------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/config/CLoadableOptions.h>
#include <mrpt/containers/deepcopy_poly_ptr.h>
#include <mrpt/maps/CLandmarksMap.h>
#include <mrpt/poses/CPosePDFSOG.h>
#include <mrpt/poses/poses_frwds.h>
#include <mrpt/slam/CMetricMapsAlignmentAlgorithm.h>
#include <mrpt/slam/COccupancyGridMapFeatureExtractor.h>
#include <mrpt/typemeta/TEnumType.h>
#include <mrpt/vision/CFeatureExtraction.h>

namespace mrpt::slam
{
/** A class for aligning two multi-metric maps (with an occupancy grid maps and
 * a points map, at least) based on features extraction and matching.
 * The matching pose is returned as a Sum of Gaussians (poses::CPosePDFSOG).
 *
 *  This class can use three methods (see options.methodSelection):
 *   - amCorrelation: "Brute-force" correlation of the two maps over a
 * 2D+orientation grid of possible 2D poses.
 *   - amRobustMatch: Detection of features + RANSAC matching
 *   - amModifiedRANSAC: Detection of features + modified multi-hypothesis
 * RANSAC matching as described in was reported in the paper
 * https://www.mrpt.org/Paper%3AOccupancy_Grid_Matching
 *
 * See CGridMapAligner::Align for more instructions.
 *
 * \sa CMetricMapsAlignmentAlgorithm
 * \ingroup mrpt_slam_grp
 */
class CGridMapAligner : public mrpt::slam::CMetricMapsAlignmentAlgorithm
{
   public:
    CGridMapAligner() : options() {}
    /** The type for selecting the grid-map alignment algorithm.
     */
    enum TAlignerMethod
    {
        amRobustMatch = 0,
        amCorrelation,
        amModifiedRANSAC
    };

    /** The ICP algorithm configuration data
     */
    class TConfigParams : public mrpt::config::CLoadableOptions
    {
       public:
        /** Initializer for default values:
         */
        TConfigParams();

        void loadFromConfigFile(
            const mrpt::config::CConfigFileBase& source,
            const std::string& section) override;  // See base docs
        void dumpToTextStream(
            std::ostream& out) const override;  // See base docs

        /** The aligner method: */
        TAlignerMethod methodSelection{CGridMapAligner::amModifiedRANSAC};

        /** The feature descriptor to use: 0=detector already has descriptor, 1=
         * SIFT, 2=SURF, 4=Spin images, 8=Polar images, 16=log-polar images */
        mrpt::vision::TDescriptorType feature_descriptor{
            mrpt::vision::descPolarImages};

        /** All the parameters for the feature detector. */
        mrpt::vision::CFeatureExtraction::TOptions feature_detector_options;

        /** RANSAC-step options:
         * \sa CICP::robustRigidTransformation
         */
        /** The ratio of landmarks that must be inliers to accepto an hypotheses
         * (typ: 0.20) */
        float ransac_minSetSizeRatio{0.20f};
        /** The square root of the uncertainty normalization variance var_m (see
         * papers...) */
        float ransac_SOG_sigma_m{0.10f};

        /** [amRobustMatch method only] RANSAC-step options:
         * \sa CICP::robustRigidTransformation
         */
        float ransac_mahalanobisDistanceThreshold{6.0f};

        /** [amModifiedRANSAC method only] The quantile used for chi-square
         * thresholding (default=0.99) */
        double ransac_chi2_quantile{0.99};

        /** Probability of having a good inliers (def:0,9999), used for
         * automatic number of iterations */
        double ransac_prob_good_inliers{0.9999};
        /** Features extraction from grid map: How many features to extract */
        float featsPerSquareMeter{0.015f};
        /** Correspondences are considered if their distances are below this
         * threshold (in the range [0,1]) (default=0.15). */
        float threshold_max{0.15f};
        /** Correspondences are considered if their distances to the best match
         * are below this threshold (in the range [0,1]) (default=0.15). */
        float threshold_delta{0.10f};

        /** The minimum goodness (0-1) of the post-matching ICP to accept a
         * hypothesis as good (default=0.30) */
        float min_ICP_goodness{0.30f};
        /** The maximum Mahalanobis distance between the initial and final poses
         * in the ICP not to discard the hypothesis (default=10) */
        double max_ICP_mahadist{10.0};
        /** Maximum KL-divergence for merging modes of the SOG (default=0.9) */
        double maxKLd_for_merge{0.9};

        /** DEBUG - Dump all feature correspondences in a directory "grid_feats"
         */
        bool save_feat_coors{false};
        /** DEBUG - Show graphs with the details of each feature correspondences
         */
        bool debug_show_corrs{false};
        /** DEBUG - Save the pair of maps with all the pairings. */
        bool debug_save_map_pairs{false};

    } options;

    /** The ICP algorithm return information.
     */
    struct TReturnInfo : public TMetricMapAlignmentResult
    {
        TReturnInfo() = default;
        virtual ~TReturnInfo() override = default;

        /** A goodness measure for the alignment, it is a [0,1] range indicator
         * of percentage of correspondences.
         */
        float goodness{0};

        /** The "brute" estimation from using all the available correspondences,
         * provided just for comparison purposes (it is not the robust
         * estimation, available as the result of the Align method).
         */
        mrpt::poses::CPose2D noRobustEstimation;

        /** The different SOG densities at different steps of the algorithm:
         *   - sog1 : Directly from the matching of features
         *   - sog2 : Merged of sog1
         *   - sog3 : sog2 refined with ICP
         *
         *   - The final sog is the merge of sog3.
         *
         */
        mrpt::containers::deepcopy_poly_ptr<mrpt::poses::CPosePDFSOG::Ptr> sog1,
            sog2, sog3;

        /** The landmarks of each map (the indices of these landmarks correspond
         * to those in "correspondences")  */
        mrpt::maps::CLandmarksMap::Ptr landmarks_map1, landmarks_map2;

        /** All the found correspondences (not consistent) */
        mrpt::tfest::TMatchingPairList correspondences;

        struct TPairPlusDistance
        {
            TPairPlusDistance(size_t i1, size_t i2, float d)
                : idx_this(i1), idx_other(i2), dist(d)
            {
            }
            size_t idx_this, idx_other;
            float dist;
        };

        /** Mahalanobis distance for each potential correspondence */
        std::vector<TPairPlusDistance> correspondences_dists_maha;

        /** The ICP goodness of all potential SOG modes at the stage "sog2",
         * thus before the removing of "bad" ICP matches. */
        std::vector<double> icp_goodness_all_sog_modes;
    };

    /** The method for aligning a pair of 2D points map.
     *   The meaning of some parameters are implementation dependant,
     *    so look for derived classes for instructions.
     *  The target is to find a PDF for the pose displacement between
     *   maps, thus <b>the pose of m2 relative to m1</b>. This pose
     *   is returned as a PDF rather than a single value.
     *
     *  NOTE: This method can be configurated with "options"
     *
     * \param m1            [IN] The first map (Must be a
     *mrpt::maps::CMultiMetricMap
     *class)
     * \param m2            [IN] The second map (Must be a
     *mrpt::maps::CMultiMetricMap
     *class)
     * \param initialEstimationPDF  [IN] (IGNORED IN THIS ALGORITHM!)
     * \param runningTime   [OUT] A pointer to a container for obtaining the
     *algorithm running time in seconds, or NULL if you don't need it.
     * \param info          [OUT] A pointer to a TReturnInfo struct, or NULL if
     *result information are not required.
     *
     * \note The returned PDF depends on the selected alignment method:
     *      - "amRobustMatch" --> A "poses::CPosePDFSOG" object.
     *      - "amCorrelation" --> A "poses::CPosePDFGrid" object.
     *
     * \return A smart pointer to the output estimated pose PDF.
     * \sa CPointsMapAlignmentAlgorithm, options
     */
    mrpt::poses::CPosePDF::Ptr AlignPDF(
        const mrpt::maps::CMetricMap* m1, const mrpt::maps::CMetricMap* m2,
        const mrpt::poses::CPosePDFGaussian& initialEstimationPDF,
        mrpt::optional_ref<TMetricMapAlignmentResult> outInfo =
            std::nullopt) override;

    /** Not applicable in this class, will launch an exception if used. */
    mrpt::poses::CPose3DPDF::Ptr Align3DPDF(
        const mrpt::maps::CMetricMap* m1, const mrpt::maps::CMetricMap* m2,
        const mrpt::poses::CPose3DPDFGaussian& initialEstimationPDF,
        mrpt::optional_ref<TMetricMapAlignmentResult> outInfo =
            std::nullopt) override;

   private:
    /** Private member, implements one the algorithms.
     */
    mrpt::poses::CPosePDF::Ptr AlignPDF_correlation(
        const mrpt::maps::CMetricMap* m1, const mrpt::maps::CMetricMap* m2,
        const mrpt::poses::CPosePDFGaussian& initialEstimationPDF,
        TReturnInfo& info);

    /** Private member, implements both, the "robustMatch" and the newer
     * "modifiedRANSAC" algorithms.
     */
    mrpt::poses::CPosePDF::Ptr AlignPDF_robustMatch(
        const mrpt::maps::CMetricMap* m1, const mrpt::maps::CMetricMap* m2,
        const mrpt::poses::CPosePDFGaussian& initialEstimationPDF,
        TReturnInfo& info);

    /** Grid map features extractor */
    COccupancyGridMapFeatureExtractor m_grid_feat_extr;
};

}  // namespace mrpt::slam
MRPT_ENUM_TYPE_BEGIN(mrpt::slam::CGridMapAligner::TAlignerMethod)
using namespace mrpt::slam;
MRPT_FILL_ENUM_MEMBER(CGridMapAligner, amRobustMatch);
MRPT_FILL_ENUM_MEMBER(CGridMapAligner, amCorrelation);
MRPT_FILL_ENUM_MEMBER(CGridMapAligner, amModifiedRANSAC);
MRPT_ENUM_TYPE_END()