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https://issues.apache.org/jira/browse/MATH-668?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Luc Maisonobe resolved MATH-668.
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Resolution: Not A Problem
Fix Version/s: (was: 3.1)
3.0
I agree with Thomas analyses.
Concerning the difference2 case, the two points are explained by the vertical
line at x = 5.0 which comes from the outer shape. The internal representation
is a BSP tree and one of this part of the outer boundary creates an hyperplane
that splits the inner triangle. When the boundary representation is rebuilt,
the two segments are glued together and the points appear there. There is no
post-processing that simplifies the representation afterwards.
Concerning the circle test, I guess you mixed the arrays. What is really in the
code is that the vertices2 array is build first from outer circle and the
vertices1 array is built afterwards from inner circle. So you are really
subtracting a big disk from a smaller one. As Thomas explained, computing set2
minus set1 give the expected two boundaries. Another possible change is to
build the circles clockwise instead of counter-clockwise, and in this case the
two regions are infinite wich a whole at the center, then subtracting set2 from
set1 returns a disk with a hole.
> Polygon difference function produces erroneous results with certain polygons
> ----------------------------------------------------------------------------
>
> Key: MATH-668
> URL: https://issues.apache.org/jira/browse/MATH-668
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.0
> Reporter: Curtis Jensen
> Assignee: Luc Maisonobe
> Labels: difference, math,, polygon,
> Fix For: 3.0
>
> Attachments: PolygonsSetCircleTest.java, PolygonsSetTest.java
>
> Original Estimate: 168h
> Remaining Estimate: 168h
>
> For some polygons, the difference function produces erroneous results. This
> appears to happen when one polygon is completely encompassed in another, and
> the outer has multiple concave sections.
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