Added RadiusNthSelector

cadquery/selectors.py

@@ -300,6 +300,51 @@ def filter(self, objectList):
         return r
 
 
+class RadiusNthSelector(Selector):
+    """
+    Select the object with the Nth radius.
+
+    Applicability:
+        All Edge and Wires.
+
+    Will ignore any shape that can not be represented as a circle or an arc of
+    a circle.
+    """
+
+    def __init__(self, n, directionMax=True, tolerance=0.0001):
+        self.N = n
+        self.directionMax = directionMax
+        self.TOLERANCE = tolerance
+
+    def filter(self, objectList):
+        # calculate how many digits of precision do we need
+        digits = -math.floor(math.log10(self.TOLERANCE))
+
+        # make a radius dict
+        # this is one to many mapping so I am using a default dict with list
+        objectDict = defaultdict(list)
+        for el in objectList:
+            try:
+                rad = el.radius()
+            except ValueError:
+                continue
+            objectDict[round(rad, digits)].append(el)
+
+        # choose the Nth unique rounded distance
+        sortedObjectList = sorted(
+            list(objectDict.keys()), reverse=not self.directionMax
+        )
+        try:
+            nth_distance = sortedObjectList[self.N]
+        except IndexError:
+            raise IndexError(
+                f"Attempted to access the {self.N}-th radius in a list {len(sortedObjectList)} long"
+            )
+
+        # map back to original objects and return
+        return objectDict[nth_distance]
+
+
 class DirectionMinMaxSelector(Selector):
     """
         Selects objects closest or farthest in the specified direction

doc/apireference.rst

@@ -176,6 +176,7 @@ as a basis for futher operations.
         ParallelDirSelector
         DirectionSelector
         DirectionNthSelector
+        RadiusNthSelector
         PerpendicularDirSelector
         TypeSelector
         DirectionMinMaxSelector

doc/classreference.rst

@@ -61,6 +61,7 @@ Selector Classes
     ParallelDirSelector
     DirectionSelector
     DirectionNthSelector
+    RadiusNthSelector
     PerpendicularDirSelector
     TypeSelector
     DirectionMinMaxSelector

tests/test_selectors.py

@@ -391,6 +391,84 @@ def testBox(self):
         ).vals()
         self.assertEqual(1, len(fl))
 
+    def testRadiusNthSelector(self):
+        part = (
+            Workplane()
+            .box(10, 10, 1)
+            .edges(">(1, 1, 0) and |Z")
+            .fillet(1)
+            .edges(">(-1, 1, 0) and |Z")
+            .fillet(1)
+            .edges(">(-1, -1, 0) and |Z")
+            .fillet(2)
+            .edges(">(1, -1, 0) and |Z")
+            .fillet(3)
+            .faces(">Z")
+        )
+        # smallest radius is 1.0
+        self.assertAlmostEqual(
+            part.edges(selectors.RadiusNthSelector(0)).val().radius(), 1.0
+        )
+        # there are two edges with the smallest radius
+        self.assertEqual(len(part.edges(selectors.RadiusNthSelector(0)).vals()), 2)
+        # next radius is 2.0
+        self.assertAlmostEqual(
+            part.edges(selectors.RadiusNthSelector(1)).val().radius(), 2.0
+        )
+        # largest radius is 3.0
+        self.assertAlmostEqual(
+            part.edges(selectors.RadiusNthSelector(-1)).val().radius(), 3.0
+        )
+        # accessing index 3 should be an IndexError
+        with self.assertRaises(IndexError):
+            part.edges(selectors.RadiusNthSelector(3))
+        # reversed
+        self.assertAlmostEqual(
+            part.edges(selectors.RadiusNthSelector(0, directionMax=False))
+            .val()
+            .radius(),
+            3.0,
+        )
+
+        # test the selector on wires
+        wire_circles = (
+            Workplane()
+            .circle(2)
+            .moveTo(10, 0)
+            .circle(2)
+            .moveTo(20, 0)
+            .circle(4)
+            .consolidateWires()
+        )
+        self.assertEqual(
+            len(wire_circles.wires(selectors.RadiusNthSelector(0)).vals()), 2
+        )
+        self.assertEqual(
+            len(wire_circles.wires(selectors.RadiusNthSelector(1)).vals()), 1
+        )
+        self.assertAlmostEqual(
+            wire_circles.wires(selectors.RadiusNthSelector(0)).val().radius(), 2
+        )
+        self.assertAlmostEqual(
+            wire_circles.wires(selectors.RadiusNthSelector(1)).val().radius(), 4
+        )
+
+        # a polygon with rounded corners has a radius, according to OCCT
+        loop_wire = Wire.makePolygon(
+            [Vector(-10, 0, 0), Vector(0, 10, 0), Vector(10, 0, 0),]
+        )
+        loop_workplane = (
+            Workplane().add(loop_wire.offset2D(1)).add(loop_wire.offset2D(2))
+        )
+        self.assertAlmostEqual(
+            loop_workplane.wires(selectors.RadiusNthSelector(0)).val().radius(), 1.0
+        )
+        self.assertAlmostEqual(
+            loop_workplane.wires(selectors.RadiusNthSelector(1)).val().radius(), 2.0
+        )
+        with self.assertRaises(IndexError):
+            loop_workplane.wires(selectors.RadiusNthSelector(2))
+
     def testAndSelector(self):
         c = CQ(makeUnitCube())