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https://issues.apache.org/jira/browse/MATH-880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13479093#comment-13479093
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Luc Maisonobe commented on MATH-880:
------------------------------------
Curtis, I was wondering if the API we propose for building the polygons is a
good one.
It was created this way because it is dimension-independent and is in fact
implemented at a rather high level (in the AbstractRegion class).
Perhaps we should provide you an additional way to build polygons, which would
be 2D-specific and would not lose topologic information like the general case
obviously does now. When you build your polygons, do you have some additional
knowledge about it? It seems you already have continuous loops and have
organized your points in a logical way. Is this always the case? Could we
assume that you know how the various segments are connected together, could we
assume you always have closed shapes, could we assume you loops around the
shapes with the inside on your left? If so, do you think having a dedicated API
for 2D-polygons would be useful to you?
> Polygon difference produces erronious results in some cases
> -----------------------------------------------------------
>
> Key: MATH-880
> URL: https://issues.apache.org/jira/browse/MATH-880
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.0
> Reporter: Curtis Jensen
> Fix For: 3.1
>
> Attachments: PolygonDiffAll.png, PolygonDiffResults.png,
> PolygonInputs.png
>
>
> The 2D polygon difference method is returning incorrect
> results. Below is a test case of subtracting two polygons (Sorry,
> this is the simplest case that I could find that duplicates the
> problem).
> There are three problems with the result. The first is that the first
> point of the first set of vertices is null (and the first point of the
> second set is also null). The second is that, even if the first null
> points are ignored, the returned polygon is not the correct result.
> The first and last points are way off, and the remaining points do not
> match the original polygon boundaries. Additionally, there are two
> holes that are returned in the results. This subtraction case should
> not have holes.
> {code:title="Complex Polygon Difference Test"}
> public void testComplexDifference() {
> Vector2D[][] vertices1 = new Vector2D[][] {
> new Vector2D[] {
> new Vector2D( 90.08714908223715, 38.370299337260235),
> new Vector2D( 90.08709517675004, 38.3702895991413),
> new Vector2D( 90.08401538704919, 38.368849330127944),
> new Vector2D( 90.08258210430711, 38.367634558585564),
> new Vector2D( 90.08251455106665, 38.36763409247078),
> new Vector2D( 90.08106599752608, 38.36761621664249),
> new Vector2D( 90.08249585300035, 38.36753627557965),
> new Vector2D( 90.09075743352184, 38.35914647644972),
> new Vector2D( 90.09099945896571, 38.35896264724079),
> new Vector2D( 90.09269383800086, 38.34595756121246),
> new Vector2D( 90.09638631543191, 38.3457988093121),
> new Vector2D( 90.09666417351019, 38.34523360999418),
> new Vector2D( 90.1297082145872, 38.337670454923625),
> new Vector2D( 90.12971687748956, 38.337669827794684),
> new Vector2D( 90.1240820219179, 38.34328502001131),
> new Vector2D( 90.13084259656404, 38.34017811765017),
> new Vector2D( 90.13378567942857, 38.33860579180606),
> new Vector2D( 90.13519557833206, 38.33621054663689),
> new Vector2D( 90.13545616732307, 38.33614965452864),
> new Vector2D( 90.13553111202748, 38.33613962818305),
> new Vector2D( 90.1356903436448, 38.33610227127048),
> new Vector2D( 90.13576283227428, 38.33609255422783),
> new Vector2D( 90.13595870833188, 38.33604606376991),
> new Vector2D( 90.1361556630693, 38.3360024198866),
> new Vector2D( 90.13622408795709, 38.335987048115726),
> new Vector2D( 90.13696189099994, 38.33581914328681),
> new Vector2D( 90.13746655304897, 38.33616706665265),
> new Vector2D( 90.13845973716064, 38.33650776167099),
> new Vector2D( 90.13950901827667, 38.3368469456463),
> new Vector2D( 90.14393814424852, 38.337591835857495),
> new Vector2D( 90.14483839716831, 38.337076122362475),
> new Vector2D( 90.14565474433601, 38.33769000964429),
> new Vector2D( 90.14569421179482, 38.3377117256905),
> new Vector2D( 90.14577067124333, 38.33770883625908),
> new Vector2D( 90.14600350631684, 38.337714326520995),
> new Vector2D( 90.14600355139731, 38.33771435193319),
> new Vector2D( 90.14600369112401, 38.33771443882085),
> new Vector2D( 90.14600382486884, 38.33771453466096),
> new Vector2D( 90.14600395205912, 38.33771463904344),
> new Vector2D( 90.14600407214999, 38.337714751520764),
> new Vector2D( 90.14600418462749, 38.337714871611695),
> new Vector2D( 90.14600422249327, 38.337714915811034),
> new Vector2D( 90.14867838361471, 38.34113888210675),
> new Vector2D( 90.14923750157374, 38.341582537502575),
> new Vector2D( 90.14877083250991, 38.34160685841391),
> new Vector2D( 90.14816667319519, 38.34244232585684),
> new Vector2D( 90.14797696744586, 38.34248455284745),
> new Vector2D( 90.14484318014337, 38.34385573215269),
> new Vector2D( 90.14477919958296, 38.3453797747614),
> new Vector2D( 90.14202393306448, 38.34464324839456),
> new Vector2D( 90.14198920640195, 38.344651155237216),
> new Vector2D( 90.14155207025175, 38.34486424263724),
> new Vector2D( 90.1415196143314, 38.344871730519),
> new Vector2D( 90.14128611910814, 38.34500196593859),
> new Vector2D( 90.14047850603913, 38.34600084496253),
> new Vector2D( 90.14045907000337, 38.34601860032171),
> new Vector2D( 90.14039496493928, 38.346223030432384),
> new Vector2D( 90.14037626063737, 38.346240203360026),
> new Vector2D( 90.14030005823724, 38.34646920000705),
> new Vector2D( 90.13799164754806, 38.34903093011013),
> new Vector2D( 90.11045289492762, 38.36801537312368),
> new Vector2D( 90.10871471476526, 38.36878044144294),
> new Vector2D( 90.10424901707671, 38.374300101757),
> new Vector2D( 90.10263482039932, 38.37310041316073),
> new Vector2D( 90.09834601753448, 38.373615053823414),
> new Vector2D( 90.0979455456843, 38.373578376172475),
> new Vector2D( 90.09086514328669, 38.37527884194668),
> new Vector2D( 90.09084931407364, 38.37590801712463),
> new Vector2D( 90.09081227075944, 38.37526295920463),
> new Vector2D( 90.09081378927135, 38.375193883266434)
> }
> };
> PolygonsSet set1 = buildSet(vertices1);
> Vector2D[][] vertices2 = new Vector2D[][] {
> new Vector2D[] {
> new Vector2D( 90.13067558880044, 38.36977255037573),
> new Vector2D( 90.12907570488, 38.36817308242706),
> new Vector2D( 90.1342774136516, 38.356886880294724),
> new Vector2D( 90.13090330629757, 38.34664392676211),
> new Vector2D( 90.13078571364593, 38.344904617518466),
> new Vector2D( 90.1315602208914, 38.3447185040846),
> new Vector2D( 90.1316336226821, 38.34470643148342),
> new Vector2D( 90.134020944832, 38.340936644972885),
> new Vector2D( 90.13912536387306, 38.335497255122334),
> new Vector2D( 90.1396178806582, 38.334878075552126),
> new Vector2D( 90.14083049696671, 38.33316530644106),
> new Vector2D( 90.14145252901329, 38.33152722916191),
> new Vector2D( 90.1404779335565, 38.32863516047786),
> new Vector2D( 90.14282712131586, 38.327504432532066),
> new Vector2D( 90.14616669875488, 38.3237354115015),
> new Vector2D( 90.14860976050608, 38.315714862457924),
> new Vector2D( 90.14999277782437, 38.3164932507504),
> new Vector2D( 90.15005207194997, 38.316534677663356),
> new Vector2D( 90.15508513859612, 38.31878731691609),
> new Vector2D( 90.15919938519221, 38.31852743183782),
> new Vector2D( 90.16093758658837, 38.31880662005153),
> new Vector2D( 90.16099420184912, 38.318825953291594),
> new Vector2D( 90.1665411125756, 38.31859497874757),
> new Vector2D( 90.16999653861313, 38.32505772048029),
> new Vector2D( 90.17475243391698, 38.32594398441148),
> new Vector2D( 90.17940844844992, 38.327427213761325),
> new Vector2D( 90.20951909541378, 38.330616833491774),
> new Vector2D( 90.2155400467941, 38.331746223670336),
> new Vector2D( 90.21559881391778, 38.33175551425302),
> new Vector2D( 90.21916646426041, 38.332584299620805),
> new Vector2D( 90.23863749852285, 38.34778978875795),
> new Vector2D( 90.25459855175802, 38.357790570608984),
> new Vector2D( 90.25964298227257, 38.356918010203174),
> new Vector2D( 90.26024593994703, 38.361692743151366),
> new Vector2D( 90.26146187570015, 38.36311080550837),
> new Vector2D( 90.26614159359622, 38.36510808579902),
> new Vector2D( 90.26621342936448, 38.36507942500333),
> new Vector2D( 90.26652190211962, 38.36494042196722),
> new Vector2D( 90.26621240678867, 38.365113172030874),
> new Vector2D( 90.26614057102057, 38.365141832826794),
> new Vector2D( 90.26380080055299, 38.3660381760273),
> new Vector2D( 90.26315345241, 38.36670658276421),
> new Vector2D( 90.26251574942881, 38.367490323488084),
> new Vector2D( 90.26247873448426, 38.36755266444749),
> new Vector2D( 90.26234628016698, 38.36787989125406),
> new Vector2D( 90.26214559424784, 38.36945909356126),
> new Vector2D( 90.25861728442555, 38.37200753430875),
> new Vector2D( 90.23905557537864, 38.375405314295904),
> new Vector2D( 90.22517251874075, 38.38984691662256),
> new Vector2D( 90.22549955153215, 38.3911564273979),
> new Vector2D( 90.22434386063355, 38.391476432092134),
> new Vector2D( 90.22147729457276, 38.39134652252034),
> new Vector2D( 90.22142070120117, 38.391349167741964),
> new Vector2D( 90.20665060751588, 38.39475580900313),
> new Vector2D( 90.20042268367109, 38.39842558622888),
> new Vector2D( 90.17423771242085, 38.402727751805344),
> new Vector2D( 90.16756796257476, 38.40913898597597),
> new Vector2D( 90.16728283954308, 38.411255399912875),
> new Vector2D( 90.16703538220418, 38.41136059866693),
> new Vector2D( 90.16725865657685, 38.41013618805954),
> new Vector2D( 90.16746107640665, 38.40902614307544),
> new Vector2D( 90.16122795307462, 38.39773101873203)
> }
> };
> PolygonsSet set2 = buildSet(vertices2);
> PolygonsSet set = (PolygonsSet) new
> RegionFactory<Euclidean2D>().difference(set1.copySelf(),
> set2.copySelf());
> Vector2D[][] verticies = set.getVertices();
> Assert.assertTrue(verticies[0][0] != null);
> Assert.assertEquals(1, verticies.length);
> }
> {code}
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