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https://issues.apache.org/jira/browse/MATH-1266?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Luc Maisonobe resolved MATH-1266.
---------------------------------
Resolution: Fixed
Fix Version/s: 3.6
4.0
Fixed in git repository (commit 2091cfb for branch master, commit 50c5eae for
branch MATH_3_X)
> split and side methods may be inconsistent in BSP trees
> -------------------------------------------------------
>
> Key: MATH-1266
> URL: https://issues.apache.org/jira/browse/MATH-1266
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.5
> Reporter: Luc Maisonobe
> Assignee: Luc Maisonobe
> Fix For: 4.0, 3.6
>
>
> In BSP trees, there are two related methods dealing with the relative
> position of a sub-hyperplane and an hyperplane: side and split.
> sub.side(hyperplane) returns an enumerate (PLUS, MINUS, BOTH, HYPER) telling
> the relative position of the syb-hyperplane with respect to the hyperplane.
> sub.split(hyperplane) splits the sub-hyperplane in two parts, one on the plus
> side of the hyperplane and one on the minus side of the hyperplane.
> These methods should be consistent, i.e. when side returns BOTH, then split
> should return two non-null parts. This fails in the following case:
> {code}
> @Test
> public void testSideSplitConsistency() {
> double tolerance = 1.0e-6;
> Circle hyperplane = new Circle(new Vector3D(9.738804529764676E-5,
> -0.6772824575010357, -0.7357230887208355),
> tolerance);
> SubCircle sub = new SubCircle(new Circle(new
> Vector3D(2.1793884139073498E-4, 0.9790647032675541, -0.20354915700704285),
> tolerance),
> new ArcsSet(4.7121441684170700,
> 4.7125386635004760, tolerance));
> SplitSubHyperplane<Sphere2D> split = sub.split(hyperplane);
> Assert.assertNotNull(split.getMinus());
> Assert.assertNull(split.getPlus());
> Assert.assertEquals(Side.MINUS, sub.side(hyperplane));
> }
> {code}
> Here, side returns BOTH but the plus part is null. This is due to the plus
> side being smaller than the tolerance (1.0e-6 here) and filtered out in the
> split methods whereas it is not filtered out in the side method, which has a
> slightly different algorithm. So instead of returning BOTH, side should
> return MINUS as it should filter out the too small plus part.
> In fact, it is only one particular case, the same could occur in other spaces
> (Euclidean or Spherical, and on various dimensions).
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