Added AreaNthSelector

cadquery/selectors.py

@@ -17,9 +17,19 @@
  License along with this library; If not, see <http://www.gnu.org/licenses/>
 """
 
+from abc import abstractmethod, ABC
 import math
 from .occ_impl.geom import Vector
-from .occ_impl.shapes import Shape, Edge, Face, Wire, geom_LUT_EDGE, geom_LUT_FACE
+from .occ_impl.shapes import (
+ Shape,
+ Edge,
+ Face,
+ Wire,
+ Shell,
+ Solid,
+ geom_LUT_EDGE,
+ geom_LUT_FACE,
+)
 from pyparsing import (
  Literal,
  Word,
@@ -37,7 +47,7 @@
  Keyword,
 )
 from functools import reduce
-from typing import List, Union, Sequence
+from typing import List, Union, Sequence, cast
 
 
 class Selector(object):
@@ -294,7 +304,7 @@ def filter(self, objectList: Sequence[Shape]) -> List[Shape]:
  return r
 
 
-class _NthSelector(Selector):
+class _NthSelector(Selector, ABC):
  """
  An abstract class that provides the methods to select the Nth object/objects of an ordered list.
  """
@@ -324,6 +334,7 @@ def filter(self, objectlist: Sequence[Shape]) -> List[Shape]:
 
  return out
 
+ @abstractmethod
  def key(self, obj: Shape) -> float:
  """
  Return the key for ordering. Can raise a ValueError if obj can not be
@@ -454,6 +465,82 @@ def filter(self, objectlist: Sequence[Shape]) -> List[Shape]:
  return objectlist
 
 
+class LengthNthSelector(_NthSelector):
+ """
+ Select the object(s) with the Nth length
+
+ Applicability:
+ All Edge and Wire objects
+ """
+
+ def key(self, obj: Shape) -> float:
+ if isinstance(obj, (Edge, Wire)):
+ return obj.Length()
+ else:
+ raise ValueError(
+ f"LengthNthSelector supports only Edges and Wires, not {type(obj).__name__}"
+ )
+
+
+class AreaNthSelector(_NthSelector):
+ """
+ Selects the object(s) with Nth area
+
+ Applicability:
+ Faces, Shells, Solids - Shape.Area() is used to compute area
+ planar Wires - a temporary face is created to compute area
+
+ Among other things can be used to select one of 
+ the nested coplanar wires or faces. 
+
+ For example to create a fillet on a shank:
+
+ result = (
+ cq.Workplane("XY")
+ .circle(5)
+ .extrude(2)
+ .circle(2)
+ .extrude(10)
+ .faces(">Z[-2]")
+ .wires(AreaNthSelector(0))
+ .fillet(2)
+ )
+
+ Or to create a lip on a case seam:
+
+ result = (
+ cq.Workplane("XY")
+ .rect(20, 20)
+ .extrude(10)
+ .edges("|Z or <Z")
+ .fillet(2)
+ .faces(">Z")
+ .shell(2)
+ .faces(">Z")
+ .wires(AreaNthSelector(-1))
+ .toPending()
+ .workplane()
+ .offset2D(-1)
+ .extrude(1)
+ .faces(">Z[-2]")
+ .wires(AreaNthSelector(0))
+ .toPending()
+ .workplane()
+ .cutBlind(2)
+ )
+ """
+
+ def key(self, obj: Shape) -> float:
+ if isinstance(obj, (Face, Shell, Solid)):
+ return obj.Area()
+ elif isinstance(obj, Wire):
+ return Face.makeFromWires(obj).Area()
+ else:
+ raise ValueError(
+ f"AreaNthSelector supports only Wires, Faces, Shells and Solids, not {type(obj).__name__}"
+ )
+
+
 class BinarySelector(Selector):
  """
  Base class for selectors that operates with two other

doc/apireference.rst

@@ -177,6 +177,8 @@ as a basis for futher operations.
  ParallelDirSelector
  DirectionSelector
  DirectionNthSelector
+ LengthNthSelector
+ AreaNthSelector
  RadiusNthSelector
  PerpendicularDirSelector
  TypeSelector

doc/classreference.rst

@@ -66,6 +66,8 @@ Selector Classes
  CenterNthSelector
  DirectionMinMaxSelector
  DirectionNthSelector
+ LengthNthSelector
+ AreaNthSelector
  BinarySelector
  AndSelector
  SumSelector

examples/Ex026_Case_Seam_Lip.py

@@ -0,0 +1,47 @@
+import cadquery as cq
+from cadquery.selectors import AreaNthSelector
+
+case_bottom = (
+ cq.Workplane("XY")
+ .rect(20, 20)
+ .extrude(10) # solid 20x20x10 box
+ .edges("|Z or <Z")
+ .fillet(2) # rounding all edges except 4 edges of the top face
+ .faces(">Z")
+ .shell(2) # shell of thickness 2 with top face open
+ .faces(">Z")
+ .wires(AreaNthSelector(-1)) # selecting top outer wire
+ .toPending()
+ .workplane()
+ .offset2D(-1) # creating centerline wire of case seam face
+ .extrude(1) # covering the sell with temporary "lid"
+ .faces(">Z[-2]")
+ .wires(AreaNthSelector(0)) # selecting case crossection wire
+ .toPending()
+ .workplane()
+ .cutBlind(2) # cutting through the "lid" leaving a lip on case seam surface
+)
+
+# similar process repeated for the top part
+# but instead of "growing" an inner lip
+# material is removed inside case seam centerline
+# to create an outer lip
+case_top = (
+ cq.Workplane("XY")
+ .move(25)
+ .rect(20, 20)
+ .extrude(5)
+ .edges("|Z or >Z")
+ .fillet(2)
+ .faces("<Z")
+ .shell(2)
+ .faces("<Z")
+ .wires(AreaNthSelector(-1))
+ .toPending()
+ .workplane()
+ .offset2D(-1)
+ .cutBlind(-1)
+)
+
+show_object(case_bottom)
+show_object(case_top, options={"alpha": 0.5})

tests/__init__.py

@@ -47,9 +47,9 @@ def toTuple(v):
 
 
 class BaseTest(unittest.TestCase):
- def assertTupleAlmostEquals(self, expected, actual, places):
+ def assertTupleAlmostEquals(self, expected, actual, places, msg=None):
  for i, j in zip(actual, expected):
- self.assertAlmostEqual(i, j, places)
+ self.assertAlmostEqual(i, j, places, msg=msg)
 
 
 __all__ = [