zorder_knn is a C++ header-only library that implements a floating point morton order comparison operator1 for n-dimensional points.
Before running CMake, run either build-extern.cmd or build-extern.sh to download and build the necessary external dependencies in the .extern directory. You may skip this step if you don't want to run the unit tests.
#include <zorder_knn/less.hpp>
constexpr std::size_t n = 2;
using Point = std:array<float, n>;
std::vector<Point> pts;
// ...
std::sort(pts.begin(), pts.end(), zorder_knn::Less<Point, n>());
2000 random 2d points whose order is given by a path from start (blue) to end (red). Left: random order. Right: morton order.
[1] M. Connor and P. Kumar, "Fast construction of k-nearest neighbor graphs for point clouds," in IEEE Transactions on Visualization and Computer Graphics, vol. 16, no. 4, pp. 599-608, July-Aug. 2010, doi: 10.1109/TVCG.2010.9.