Minor Description
The is a bug on the code in MonotoneChain.java that attempts to handle the case of a point on the line formed by the previous last points and the last point of the chain being constructed. When `includeCollinearPoints` is false, the point should be dropped entirely. In common-math 3,3, the point is added, which in some cases can cause a `ConvergenceException` to be thrown.
In the patch below, the data points are from a case that showed up in testing before we went to production.
Index: src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/MonotoneChain.java
===================================================================
--- src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/MonotoneChain.java (revision 1609491)
+++ src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/MonotoneChain.java (working copy)
@@ -160,8 +160,8 @@
} else {
if (distanceToCurrent > distanceToLast) {
hull.remove(size - 1);
+ hull.add(point);
}
- hull.add(point);
}
return;
} else if (offset > 0) {
Index: src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java
===================================================================
--- src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java (revision 1609491)
+++ src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java (working copy)
@@ -204,6 +204,24 @@
}
@Test
+ public void testCollinnearPointOnExistingBoundary() {
+ final Collection<Vector2D> points = new ArrayList<Vector2D>();
+ points.add(new Vector2D(7.3152, 34.7472));
+ points.add(new Vector2D(6.400799999999997, 34.747199999999985));
+ points.add(new Vector2D(5.486399999999997, 34.7472));
+ points.add(new Vector2D(4.876799999999999, 34.7472));
+ points.add(new Vector2D(4.876799999999999, 34.1376));
+ points.add(new Vector2D(4.876799999999999, 30.48));
+ points.add(new Vector2D(6.0959999999999965, 30.48));
+ points.add(new Vector2D(6.0959999999999965, 34.1376));
+ points.add(new Vector2D(7.315199999999996, 34.1376));
+ points.add(new Vector2D(7.3152, 30.48));
+
+ final ConvexHull2D hull = generator.generate(points);
+ checkConvexHull(points, hull);
+ }
+
+ @Test
public void testIssue1123() {
List<Vector2D> points = new ArrayList<Vector2D>();