Fix hull failure with collinear circle centres

cadquery/hull.py

@@ -18,6 +18,9 @@
 Entity = Union["Arc", "Point"]
 Hull = List[Union["Arc", "Point", "Segment"]]
 
+# minimum arc span; below this makeCircle would return a full circle
+TOL = 1e-9
+
 
 class Point:
 
@@ -39,7 +42,7 @@ def __hash__(self):
 
     def __eq__(self, other):
 
-        return (self.x, self.y) == (other.x, other.y)
+        return type(self) == type(other) and (self.x, self.y) == (other.x, other.y)
 
 
 class Segment:
@@ -74,6 +77,16 @@ def __init__(self, c: Point, r: float, a1: float, a2: float):
         self.e = Point(r * cos(a2), r * sin(a2))
         self.ac = 2 * pi - (a1 - a2)
 
+    def __hash__(self):
+
+        return hash((self.c, self.r, self.a1, self.a2))
+
+    def __eq__(self, other):
+
+        return type(self) == type(other) and (
+            (self.c, self.r, self.a1, self.a2) == (other.c, other.r, other.a1, other.a2)
+        )
+
 
 def atan2p(x, y):
 
@@ -348,9 +361,10 @@ def finalize_hull(hull: Hull) -> Wire:
             a1 = degrees(atan2p(el_p.b.x - el.c.x, el_p.b.y - el.c.y))
             a2 = degrees(atan2p(el_n.a.x - el.c.x, el_n.a.y - el.c.y))
 
-            rv.append(
-                Edge.makeCircle(el.r, Vector(el.c.x, el.c.y), angle1=a1, angle2=a2)
-            )
+            if abs(a2 - a1) > TOL:
+                rv.append(
+                    Edge.makeCircle(el.r, Vector(el.c.x, el.c.y), angle1=a1, angle2=a2)
+                )
 
     el1 = hull[1]
     if isinstance(el, Segment) and isinstance(el_n, Arc) and isinstance(el1, Segment):

tests/test_hull.py

@@ -1,3 +1,6 @@
+from itertools import permutations
+from math import pi
+
 import pytest
 
 import cadquery as cq
@@ -30,3 +33,41 @@ def test_validation():
         e1 = cq.Edge.makeEllipse(2, 1)
         c1 = cq.Edge.makeCircle(0.5, (-1.5, 0.5, 0))
         hull.find_hull([c1, e1])
+
+
+def test_collinear():
+
+    r = 2.5
+    spacing = 8.0
+
+    # collinear centres let an inner circle enter the hull as a zero span arc;
+    # only some traversal orders reach it, so permute the input
+    for n in (3, 4, 5):
+
+        expected = spacing * (n - 1) * 2 * r + pi * r ** 2
+
+        for order in permutations(range(n)):
+
+            edges = [cq.Edge.makeCircle(r, (i * spacing, 0, 0)) for i in order]
+
+            h = hull.find_hull(edges)
+
+            assert h.IsClosed()
+            assert h.isValid()
+            assert cq.Face.makeFromWires(h).Area() == pytest.approx(expected)
+
+
+def test_eq():
+
+    a = hull.Arc(hull.Point(0.0, 0.0), 1.0, 0.0, 2 * pi)
+    b = hull.Arc(hull.Point(0.0, 0.0), 1.0, 0.0, 2 * pi)
+    p = hull.Point(0.0, 0.0)
+
+    assert a == b
+    assert hash(a) == hash(b)
+    assert p == hull.Point(0.0, 0.0)
+
+    assert a != hull.Arc(hull.Point(0.0, 0.0), 2.0, 0.0, 2 * pi)
+    assert a != p
+    assert p != a
+    assert a != None