Unable to complete output ring starting at ...

[cmonacaps]

geojsons referred to can be found at this gist

A production issue was reproduced by trying to union source_1.geojson and source_2.geojson.

$ geo-cli union -i source_1.geojson -i source_2.geojson
ℹ start union
◰ [Error] Unable to complete output ring starting at [-77.31806300030723, 38.975023999757816]. Last matching segment found ends at [-77.112505, 38.855774].

    at factory   polygon-clipping/dist/polygon-clipping.cjs.js:1266  throw new Error("Unable to complete output ring starting at [".concat(firstPt.x…
    at run       polygon-clipping/dist/polygon-clipping.cjs.js:1781  var ringsOut = RingOut.factory(sweepLine.segments);                             
    at union     polygon-clipping/dist/polygon-clipping.cjs.js:1797  return operation.run('union', geom, moreGeoms);                                 
    at union     lib/geo.js:43                                       coordinates: _polygonClipping.default.union((0, _geoUtil.featureToCoordinates)(…

We found we could do the union with a Python lib.

I looked at the data and it seems like there may be some rounding noise since most of the numbers have a sequence of decimal digits 999 or 000 at the 6th decimal place.

I tried rounding the numbers to the 6th dec place and this could union with polygon-clipping.

These 2 successful union results are also at the gist linked above.

Using polygon-clipping version 0.14.3 throughout this sequence of events.

I saw there is already an issue open on this error diagnostic and I honestly wasn't sure whether to post this in that thread or open a new one.

[mcdenhoed]

I have a similar simple case happening trying to union 4 squares. Code to reproduce is below:

const polygonClipping = require('polygon-clipping')

const poly1 = [[
    [1553.481712766874, 1494.8225115579035],
    [1553.481712766874, 80.60894918480847],
    [139.26815039377902, 80.60894918480824],
    [139.2681503937788, 1494.8225115579032]]]

const poly2 = [[
    [2130.363837219598, 1505.3523513000096],
    [2130.363837219598, 91.13878892691457],
    [716.1502748465028, 91.13878892691434],
    [716.1502748465026, 1505.3523513000093]
]]
const poly3 = [[
    [2162.7561633766086, 1808.0852438855597],
    [2162.7561633766086, 393.87168151246476],
    [748.5426010035136, 393.87168151246453],
    [748.5426010035134, 1808.0852438855595]
]]
const poly4 = [[
    [1522.2282522557293, 1767.4968190640373],
    [1522.2282522557293, 353.28325669094227],
    [108.01468988263434, 353.28325669094204],
    [108.01468988263412, 1767.496819064037]
]]

// This succeeds
const union = polygonClipping.union(poly1, poly2, poly3)

// This fails
const union2 = polygonClipping.union(poly1, poly2, poly3, poly4)

[mcdenhoed]

Actually in that example calling union on poly1 and poly4 is sufficient to get a crash.

[mcdenhoed]

Rounding also seems to avoid this in my case, so I guess I'll just make sure I'm rounding all inputs to polygon-clipping.

[852Kerfunkle]

I'm guessing most of these issues are related to comparing floats directly. Probably should be doing epsEqual with a sufficiently large epsilon.