Fix ZeroDivisionError in hull() for overlapping circles

cadquery/hull.py

@@ -87,7 +87,7 @@ def atan2p(x, y):
 
 def convert_and_validate(edges: Iterable[Edge]) -> Tuple[List[Arc], List[Point]]:
 
-    arcs: Set[Arc] = set()
+    arcs_by_center: dict = {}
     points: Set[Point] = set()
 
     for e in edges:
@@ -102,14 +102,16 @@ def convert_and_validate(edges: Iterable[Edge]) -> Tuple[List[Arc], List[Point]]
         elif gt == "CIRCLE":
             c = e.arcCenter()
             r = e.radius()
-            a1, a2 = e._bounds()
+            key = (c.x, c.y)
 
-            arcs.add(Arc(Point(c.x, c.y), r, a1, a2))
+            # keep one arc per center (largest radius for the hull)
+            if key not in arcs_by_center or r > arcs_by_center[key].r:
+                arcs_by_center[key] = Arc(Point(c.x, c.y), r, 0, 2 * pi)
 
         else:
             raise ValueError("Unsupported geometry {gt}")
 
-    return list(arcs), list(points)
+    return list(arcs_by_center.values()), list(points)
 
 
 def select_lowest_point(points: Points) -> Tuple[Point, int]:

tests/test_hull.py

@@ -23,6 +23,36 @@ def test_hull():
     assert h.isValid()
 
 
+def test_hull_overlapping_circles():
+    """Hull of overlapping circles should not raise ZeroDivisionError.
+
+    When two circles overlap, boolean face fusion splits them into
+    multiple arc segments sharing the same center. arc_arc() must
+    handle these concentric arcs without dividing by zero.
+    """
+    from cadquery import Sketch
+
+    s = Sketch().push([(-19, 0), (19, 0)]).circle(35).reset().hull()
+
+    assert s._faces.Area() > 0
+    assert len(s._faces.Faces()) >= 1
+
+
+def test_hull_overlapping_circles_equal_radii_via_face():
+    """Hull via .face() with overlapping equal-radii circles."""
+    from cadquery import Sketch, Location, Vector
+
+    s = (
+        Sketch()
+        .face(Sketch().circle(35).moved(Location(Vector(-19, 0, 0))))
+        .face(Sketch().circle(35).moved(Location(Vector(19, 0, 0))))
+        .hull()
+    )
+
+    assert s._faces.Area() > 0
+    assert len(s._faces.Faces()) >= 1
+
+
 def test_validation():
 
     with pytest.raises(ValueError):