[geos-commits] [SCM] GEOS branch main updated. e8d427e4f8d323b68a8f1f6d2c99e68522ec16d2

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- Log -----------------------------------------------------------------
commit e8d427e4f8d323b68a8f1f6d2c99e68522ec16d2
Author: Daniel Baston <dbaston at gmail.com>
Date:   Fri Oct 2 08:50:38 2026 -0400

    CircularArcIntersector: Avoid incorrectly classifying intersection as cocircular (#1549)

diff --git a/src/algorithm/CircularArcIntersector.cpp b/src/algorithm/CircularArcIntersector.cpp
index f08bafa54..d503fb384 100644
--- a/src/algorithm/CircularArcIntersector.cpp
+++ b/src/algorithm/CircularArcIntersector.cpp
@@ -229,16 +229,16 @@ CircularArcIntersector::intersects(const CircularArc& arc1, const CircularArc& a
         return;
     }
 
-    // a: the distance from c1 to the "radical line", which connects the two intersection points
-    // Expression rewritten by Herbie, https://herbie.uwplse.org/demo/
-    // const double a = (d*d + r1*r1 - r2*r2) / (2*d);
-    const double a = std::fma(r1-r2, (r1 + r2) / (d+d), d*0.5);
-
     // TODO because the circle center calculation is inexact we need some kind of tolerance here.
     // Take a PrecisionModel like LineIntersector?
-    if (a == 0 || (d == 0 && r1 == r2)) {
+    if (d == 0 && r1 == r2) {
         computeCocircularIntersection(arc1, arc2);
     } else {
+        // a: the distance from c1 to the "radical line", which connects the two intersection points
+        // Expression rewritten by Herbie, https://herbie.uwplse.org/demo/
+        // const double a = (d*d + r1*r1 - r2*r2) / (2*d);
+        const double a = std::fma(r1-r2, (r1 + r2) / (d+d), d*0.5);
+
         // Compute interior intersection points.
         const double dx = c2.x-c1.x;
         const double dy = c2.y-c1.y;
diff --git a/tests/unit/algorithm/CircularArcIntersectorTest.cpp b/tests/unit/algorithm/CircularArcIntersectorTest.cpp
index 6e5805b08..63695fb9b 100644
--- a/tests/unit/algorithm/CircularArcIntersectorTest.cpp
+++ b/tests/unit/algorithm/CircularArcIntersectorTest.cpp
@@ -1811,6 +1811,18 @@ void object::test<90>()
                             XY{208, 22});
 }
 
+template<>
+template<>
+void object::test<91>()
+{
+    set_test_name("two arcs with interior intersection at control point");
+
+    checkIntersection(XY{-5, 0}, XY{0, 5}, XY{5, 0},
+                      XY{-7, 0}, XY{-3, 4}, XY{1, 0},
+                      CircularArcIntersector::ONE_POINT_INTERSECTION,
+                      XY{-3, 4});
+}
+
 // TODO: check Z values of arc result centerpoints
 // TODO: add tests for seg/seg
 

-----------------------------------------------------------------------

Summary of changes:
 src/algorithm/CircularArcIntersector.cpp            | 12 ++++++------
 tests/unit/algorithm/CircularArcIntersectorTest.cpp | 12 ++++++++++++
 2 files changed, 18 insertions(+), 6 deletions(-)


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