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georust / geo

Geospatial primitives and algorithms for Rust
https://crates.io/crates/geo
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Segmentize tests #1076

Closed Robinlovelace closed 10 months ago

Robinlovelace commented 10 months ago
Robinlovelace commented 10 months ago

Not intended to be merged, more as a sanity check related to https://github.com/JosiahParry/rsgeo/issues/28 so heads-up on that @JosiahParry: seems that the Rust output is correct.

JosiahParry commented 10 months ago

The x and y values are places sequentially in your test. Use this LineString and the result returns 3 instead of 4. I'm looking into it! 

    let lns = vec![
        coord!{ x: 324957.7, y: 673670.1 },
        coord!{ x: 324957.9, y: 673680.1 },
        coord!{ x: 324959.9, y: 673686.8 },
        coord!{ x: 324961.9, y: 673693.4 },
        coord!{ x: 324963.8, y: 673699.0 },
        coord!{ x: 324969.6, y: 673710.0 },
        coord!{ x: 324976.7, y: 673722.1 },
        coord!{ x: 324996.4, y: 673742.9 }
      ];
Robinlovelace commented 10 months ago

Aha, seems like there IS a bug on the Rust side then.

Robinlovelace commented 10 months ago

Coord order updated. Curious to know the cause, it's a bit of a niche one, 100+ similar linestrings worked fine, shows value of testing on real data!

JosiahParry commented 10 months ago

In the case of this bug it is important to go into the if statement when i < (nlines - 1) but it breaks other tests in some cases. So there is some condition in this if statement that I haven't figured out. To fix the bug remove - 1 but introduces bugs elsewhere.

https://github.com/georust/geo/blob/9edfae99f1f51f3b582132da5bf9105c9635f24a/geo/src/algorithm/linestring_segment.rs#L99

JosiahParry commented 10 months ago

Got it sorted. Will make a PR shortly. Thank you!

Robinlovelace commented 10 months ago

Bingo! Quick work.