Rectfillcurve – generate rectangle-filling curves
How do you visit every coordinate in an NxM grid once? The easiest is to process line-by-line, from the first to last column, but if you want better caching you might try alternating the column direction for each row. The Morton/Z-order and Hilbert order give even better cache coherency for some tasks, although the classic versions only work on squares with power-of-two length sides. Luckily for me, people have developed generalized versions of those algorithms which can handle arbitrary-sized rectangles. I've taken those and packaged all of the those curves into "rectfillcurve", with…
In plain words
Rectfillcurve generates algorithms for visiting every coordinate in a rectangular grid exactly once, optimizing for cache performance. It implements multiple curve-filling approaches including row-by-row, alternating directions, Morton/Z-order, and Hilbert order curves, along with a pseudo-random option. The tool handles arbitrary-sized rectangles through generalized algorithms, offering an iterator API and available in both C and Python for developers working with spatial data structures.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
How do you visit every coordinate in an NxM grid once? The easiest is to process line-by-line, from the first to last column, but if you want better caching you might try alternating the column direction for each row. The Morton/Z-order and Hilbert order give even better cache coherency for some tasks, although the classic versions only work on squares with power-of-two length sides. Luckily for me, people have developed generalized versions of those algorithms which can handle arbitrary-sized rectangles. I've taken those and packaged all of the those curves into "rectfillcurve", with an iterator API for generating those curves, and a bonus "mlcg curve" with a pseudo-random visit order that should have poor cache behavior. Implemented in stand-alone C, and also available as a Python module.
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