CODEWITHSUNDEEP
c++memoryeigenpoint-cloudsopen3d
Xueshen Liu
Xueshen Liu

Reputation: 21

How to create a pointcloud from array in open3d-cpp

I am using open3d-cpp to process some pointclouds. However, the raw input is a float array (say float pts[3000], containing 1000 points), and I didn't find an efficient way to transform it into an open3d::geometry::Pointcloud, as the only parameterized constructor of Pointcloud is a copy constructor and only takes std::vector<Eigen::Vector3d> as input.

I made a naive converter, but I think it is not quite efficient, the first step is converting the float array (arr of size 40000*3) into a double array, then do the following:

    long t01 = CurrTimeMS;
    Eigen::Vector3d *vv = reinterpret_cast<Eigen::Vector3d *>(arr);
    vector<Eigen::Vector3d> vec(vv, vv+40000);
    geometry::PointCloud pcd(vec);
    long t02 = CurrTimeMS;
    std::cout << "pcd init took " << t02-t01 << " ms.\n";
    cout << (void *) vv << " " << (void *) vec.data() << " " << (void *) pcd.points_.data() << endl;

It turned out taking me 3-4ms, and because std::vector(T *start, T *end) is also a copy constructor, this code does 3 times of memory copy (all three addressed are different), which is not optimal.
Is there any more efficient way to create Pointcloud directly from memory?

Upvotes: 0

Views: 985

Answers (1)

Xueshen Liu
Xueshen Liu

Reputation: 21

I end up finding a relatively efficient approach.

std::shared_ptr<open3d::geometry::PointCloud> convert2pcd(float *data, size_t N, size_t dim=3) {
    assert(dim > 2);
    double *dd = new double[N*3];
    for (int i = 0; i < N; ++i) {
        for (int j = 0; j < 3; ++j) {
            dd[i*3+j] = (double) data[i*dim+j];
        }
    }
    Eigen::Vector3d *vv = reinterpret_cast<Eigen::Vector3d *>(dd);
    auto pcd = std::make_shared<open3d::geometry::PointCloud>();
    pcd->points_.assign(vv, vv+N);
    delete[] dd;
    return pcd;
}

which still takes me around 2-3ms.

Upvotes: 0

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