NeighborSearchCommon.h

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// ----------------------------------------------------------------------------
// -                        Open3D: www.open3d.org                            -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2024 www.open3d.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------
 
#pragma once
 
#include <nanoflann.hpp>
 
#include "open3d/utility/MiniVec.h"
 
namespace open3d {
namespace ml {
namespace impl {

enum Metric { L1, L2, Linf };
 
#ifdef __CUDACC__
#define HOST_DEVICE __host__ __device__
#else
#define HOST_DEVICE
#endif

HOST_DEVICE inline size_t SpatialHash(int x, int y, int z) {
    return x * 73856096 ^ y * 193649663 ^ z * 83492791;
}
 
HOST_DEVICE inline size_t SpatialHash(const utility::MiniVec<int, 3>& xyz) {
    return SpatialHash(xyz[0], xyz[1], xyz[2]);
}

template <class TVecf>
HOST_DEVICE inline utility::MiniVec<int, 3> ComputeVoxelIndex(
        const TVecf& pos, const typename TVecf::Scalar_t& inv_voxel_size) {
    TVecf ref_coord = pos * inv_voxel_size;
 
    utility::MiniVec<int, 3> voxel_index;
    voxel_index = floor(ref_coord).template cast<int>();
    return voxel_index;
}
#undef HOST_DEVICE

template <class T>
class Adaptor {
public:
    Adaptor(size_t num_points, const T* const data)
        : num_points(num_points), data(data) {}
 
    inline size_t kdtree_get_point_count() const { return num_points; }
 
    inline T kdtree_get_pt(const size_t idx, int dim) const {
        return data[3 * idx + dim];
    }
 
    template <class BBOX>
    bool kdtree_get_bbox(BBOX&) const {
        return false;
    }
 
private:
    size_t num_points;
    const T* const data;
};
 
template <int METRIC, class T>
struct SelectNanoflannAdaptor {};
 
template <class T>
struct SelectNanoflannAdaptor<L2, T> {
    typedef nanoflann::L2_Adaptor<T, Adaptor<T>> Adaptor_t;
};
 
template <class T>
struct SelectNanoflannAdaptor<L1, T> {
    typedef nanoflann::L1_Adaptor<T, Adaptor<T>> Adaptor_t;
};
 
}  // namespace impl
}  // namespace ml
}  // namespace open3d