polyfill_polygon returns half of the expected result

[ricardoekm]

Hello there,
When passing a world polygon (lat -90 to 90, long -180 to 180), the method polyfill_polygon returns just half of the expected results according to the resolution table.

    world_bounding_box = [
        (-90, -180),
        (-90, 180),
        (90, 180),
        (90, -180),
        (-90, -180)
    ]

  print(len(h3.polyfill_polygon(world_bounding_box, 0)))

Prints: 61

It seems an issue with the longitude interpretation. If the bounding box is split in two (long -180 to 0 and 0 to 180) and the result is combined it works fine.

    world_bounding_box_1 = [
        (-90, -180),
        (-90, 0),
        (90, 0),
        (90, -180),
        (-90, -180)
    ]

    world_bounding_box_2 = [
        (-90, 0),
        (-90, 180),
        (90, 180),
        (90, 0),
        (-90, 0)
    ]

  print(len(h3.polyfill_polygon(world_bounding_box, 0)))

[nrabinowitz]

This is currently expected behavior, but now that I look at the docs it's not well documented :/. The polyfill algo currently does not require a particular winding order, and as a result we can only take arcs < 180 degrees in length. Splitting into two boxes and filling both is the current suggested workaround.

If you just want the whole world, I think you'd be better off performance-wise with h3.get_res0_indexes and then using h3.uncompact to get the desired resolution.

[ricardoekm]

Gotcha, thanks @nrabinowitz !