Polyfill modes RFC #519
Polyfill modes RFC #519
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| consistency with the rest of the library, the `polyfill` functions should be able to use the same | ||
| cell boundaries. | ||
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| * Very large polygons |
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Do you have suggestions here? E.g. maxPolyfillSizes could return an array of sizes, and polyfillIncremental(batchNum, polygon, out) could polyfill a batch? (How this would work in the lib is still a bit fuzzy, but I think it's possible)
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I was considering if it would be possible to do this in an iterator but haven't looked into this more. We would need some allocation done, but perhaps that could be made relative to the number of points in the polygon rather than the number of cells. A simple polygon producing a large number of cells is related to the problem seen in zachasme/h3-pg#56
| * Spherical geometry consistency | ||
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| Most of the H3 library uses spherical geoemtry. For example, cell boundaries are spherical hexagons | ||
| and pentagons. The `polyfill` function is different that it assumes Cartesian geometry. For |
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Should this RFC refer to polyfill or polygonToCells?
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I'm inconsistent in the term used, but we should do a pass making that consistent. polyfill might be useful as a term as the abstract concept of filling a polygon (regardless of inclusion mode, etc).
| ## Approaches | ||
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| *What are the various options to address this issue?* | ||
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| On an API level, we will need to expose the containment mode and spherical/Cartesian choice as |
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I think we might decide in v4 that polyfill is spherical, full stop, unless it's much slower this way. But I'm not sure there's a benefit to exposing both modes to the user, and it would mean a bunch of redundant code to check point inclusion and line intersection in both ways.
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I think it was raised offline that cartesian is useful when maps are drawn on top of web mercator maps.
Co-authored-by: Nick Rabinowitz <public@nickrabinowitz.com>
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| ```js | ||
| polygonToCells(polygon, {res: res, cartesian: true, containment: h3.Containment.CENTROID}) |
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Nit: In JS, if a new object's property exactly matches a variable that will fill in that property, you can just list the property/variable name and it'll do the right thing. Eg:
| polygonToCells(polygon, {res: res, cartesian: true, containment: h3.Containment.CENTROID}) | |
| polygonToCells(polygon, {res, cartesian: true, containment: h3.Containment.CENTROID}) |
| | Bits | Meaning | ||
| | ---------- | ------- | ||
| | 1-2 (LSB) | If 0, containment mode centroid.<br>If 1, containment mode cover.<br>If 2, containment mode intersects.<br>3 is a reserved value. |
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I'd reserve more bits here, there are other possible approaches (e.g. > 50% containment). Got plenty of bits.
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As in make the flags 64 bits?
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No, as in make this bit section wider (say 3 bits instead of two) so that we don't constrain ourselves to 4 containment modes.
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