Sphericality.cpp

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/*
 
Copyright (c) 2010--2018,
François Pomerleau and Stephane Magnenat, ASL, ETHZ, Switzerland
You can contact the authors at <f dot pomerleau at gmail dot com> and
<stephane at magnenat dot net>
 
All rights reserved.
 
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modification, are permitted provided that the following conditions are met:
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      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.
 
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*/
#include "Sphericality.h"
 
 
/*
 The SphericalityDataPointFilter estimates a heuristic value which indicates how much local geometry around
 a given point resemble a plane or a sphere (uniform distribution). The value can lie in <-1,1> interval, -1 for
 perfect plane, 1 for perfectly uniform distribution. The estimation is based on three eigenvalues coming from another
 data points filter (this filter can operate only on 3D data). In the case the largest eigenvalue is zero, the filter
 outputs NaNs. If the middle eigenvalue is zero and the largest one is non-zero, the filter outputs zeros.
 
 Implemented by Vladimir Kubelka (kubelvla@gmail.com), NORLAB, Universite Laval, 2020
*/
 
// Constructor
template<typename T>
SphericalityDataPointsFilter<T>::SphericalityDataPointsFilter(const Parameters& params):
        PointMatcher<T>::DataPointsFilter("SphericalityDataPointsFilter",
                        SphericalityDataPointsFilter::availableParameters(), params),
                        keepUnstructureness(Parametrizable::get<int>("keepUnstructureness")),
                        keepStructureness(Parametrizable::get<T>("keepStructureness"))
{
}
 
// Compute
template<typename T>
typename PointMatcher<T>::DataPoints
SphericalityDataPointsFilter<T>::filter(
        const DataPoints& input)
{
        DataPoints output(input);
        inPlaceFilter(output);
        return output;
}
 
// In-place filter
template<typename T>
void SphericalityDataPointsFilter<T>::inPlaceFilter(
        DataPoints& cloud)
{
 
        typedef typename DataPoints::View View;
        typedef typename DataPoints::Label Label;
        typedef typename DataPoints::Labels Labels;
 
        const size_t pointsCount(cloud.features.cols());
        const size_t descDim(cloud.descriptors.rows());
        const size_t labelDim(cloud.descriptorLabels.size());
 
        // Check that the required eigenValue descriptor exists in the pointcloud
        if (!cloud.descriptorExists("eigValues"))
        {
                throw InvalidField("SphericalityDataPointsFilter: Error, no eigValues found in descriptors.");
        }
 
        // Validate descriptors and labels
        size_t insertDim(0);
        for(unsigned int i = 0; i < labelDim ; ++i)
                insertDim += cloud.descriptorLabels[i].span;
        if (insertDim != descDim)
                throw InvalidField("SurfaceNormalDataPointsFilter: Error, descriptor labels do not match descriptor data");
 
        // Reserve memory for new descriptors
        const size_t unidimensionalDescriptorDimension(1);
 
 
        boost::optional<View> sphericality;         // these optionals may cause a compiler warning, but it is ok,
        boost::optional<View> unstructureness;      // it is intended to be uninitialized
        boost::optional<View> structureness;
 
        Labels cloudLabels;
        cloudLabels.push_back(Label("sphericality", unidimensionalDescriptorDimension));
        if (keepUnstructureness)
                cloudLabels.push_back(Label("unstructureness", unidimensionalDescriptorDimension));
        if (keepStructureness)
                cloudLabels.push_back(Label("structureness", unidimensionalDescriptorDimension));
 
        // Reserve memory
        cloud.allocateDescriptors(cloudLabels);
 
        // Get the views
        const View eigValues = cloud.getDescriptorViewByName("eigValues");
        if (eigValues.rows() != 3)  // And check the dimensions
        {
                throw InvalidField("SphericalityDataPointsFilter: Error, the number of eigValues is not 3.");
        }
 
        sphericality = cloud.getDescriptorViewByName("sphericality");
        if (keepUnstructureness)
                unstructureness = cloud.getDescriptorViewByName("unstructureness");
        if (keepStructureness)
                structureness = cloud.getDescriptorViewByName("structureness");
 
        // Iterate through the point cloud and evaluate the Sphericality
        for (size_t i = 0; i < pointsCount; ++i)
        {
                // extract the three eigenvalues relevant to the current point
                Vector eig_vals_col = eigValues.col(i);
                // might be already sorted but sort anyway
                std::sort(eig_vals_col.data(),eig_vals_col.data()+eig_vals_col.size());
 
                // Finally, evaluate the Sphericality
                T sphericalityVal;
                T unstructurenessVal;
                T structurenessVal;
 
                // First, avoid division by zero
                //TODO: Is there a more suitable limit for considering the values almost-zero? (VK)
                if (eig_vals_col(2) < std::numeric_limits<T>::min() ||
                    eig_vals_col(1) < 0.0 ||
                    eig_vals_col(0) < 0.0)
                {
                        // If the largest eigenvalue is zero or even worse -- any of them is negative,
                        // these descriptors are not well defined (0/0 or nonsense input) and assigned NaN
                        sphericalityVal = std::numeric_limits<T>::quiet_NaN();
                        unstructurenessVal = std::numeric_limits<T>::quiet_NaN();
                        structurenessVal = std::numeric_limits<T>::quiet_NaN();
 
                } else if (eig_vals_col(1) < std::numeric_limits<T>::min()) {
                        // If there are two zero eigenvalues and one non-zero, we assign zeros to the heuristic
                        sphericalityVal = 0.0;
                        unstructurenessVal = 0.0;
                        structurenessVal = 0.0;
 
                } else {
                        // Otherwise, follow eq.(1) from Kubelka V. et al., "Radio propagation models for differential GNSS based
                        // on dense point clouds", JFR, hopefully published in 2020
                        unstructurenessVal = eig_vals_col(0) / eig_vals_col(2);
                        structurenessVal =  (eig_vals_col(1) / eig_vals_col(2)) *
                                ((eig_vals_col(1) - eig_vals_col(0)) / sqrt(eig_vals_col(0)*eig_vals_col(0) + eig_vals_col(1)*eig_vals_col(1)));
                        sphericalityVal = unstructurenessVal - structurenessVal;
                }
 
                // store it in the pointcloud
                // sphericality always
                (sphericality.get())(0,i) = sphericalityVal;
                // these two only when requested by the user
                if (unstructureness)
                        (unstructureness.get())(0,i) = unstructurenessVal;
                if (structureness)
                        (structureness.get())(0,i) = structurenessVal;
 
        }
}
 
template struct SphericalityDataPointsFilter<float>;
template struct SphericalityDataPointsFilter<double>;