Ystripes#1101
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StripeIndex buckets a ring's edges into horizontal Y stripes so PolyTree nesting tests child vertices in ~O(sqrt n) instead of O(n) per query. Wired into owner/split containment behind an edge-count threshold, with a brute-force fallback for small or adversarial rings. Includes unit, differential, and real-world QA.
Mirrors the C++ StripeIndex: per-ring Y-stripe bucketing for PolyTree nesting with a brute-force fallback below the edge-count threshold. Adds the StripeIndex test suite.
Mirrors the C++ StripeIndex: per-ring Y-stripe bucketing for PolyTree nesting with a brute-force fallback below the edge-count threshold. Adds a standalone console QA program.
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Hi Seth. |
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@AngusJohnson take your time and let me know if I can help at all |
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Hi @AngusJohnson !
A while ago, I wrote a point-in-polygon implementation for KiCad that uses ystripes. It works really well to speed things up relative to our various other algorithms that we used. Eventually, one of our clients came to us with a slow zone fill even in the new system. Profiling showed that one of the bottlenecks was in assigning hierarchy in PolyTrees for boolean ops.
To fix this, I adapted the ystripes algorithm to Clipper2 and tested with our realworld data (as well as the existing Clipper2 adversarial data). Because the algorithm doesn't work well for small polygons, it has a fail-safe that falls back to the original algo at 64 edges. For this reason, we see a worst-case speed-up of 1.0x.
What follows is my testing data on a Intel Core i9-13900KF · Debian 13 (kernel 6.12) · single-threaded, best of 5 results for both baseline and y-stripe.
-O2)-O2)fpc -O2)I couldn't find a QA system for Delphi, so I just made a small self-contained app that tested this.
I wrote this originally in C++ and ported to C# and Delphi (which are not my native languages) so please let me know if I made any mistakes. They both compile, run correctly per the QA. The C++ version is tested in KiCad as well.