CadQuery object filtering framework

cq-filter adds a few new workplane methods that take a function argument of type f: Callable[[CQObject], bool]:

• filter(f): filters Workplane objects
• sort(f): orders Workplane objects
• group(f): groups Workplane objects
• last: selects newly created faces
• toWires: select wires from selected faces

Additionally, it adds subscription support to the Workplane, allowing selection of objects quickly.

Rationale

Manipulating object selections in cadquery isn't currently possible without breaking out of the fluent API.

Using filter

Following example filters all faces with an Area of more than 100

wp = (
    wp
    .faces(">Z")
    .filter(lambda face: face.Area() > 100)
)

⚠️ values in cq/occt are often not as exact as you'd expect. For example you might expect a certain face to have an area of exactly 100 and be included when you filter the area against >= 100, but upon closer inspection it turns out the area is actually just slightly below 100 (99.999999997). Consider rounding to some sane precision, like round(face.Area(), 4)

Using sort and subscription

Following example sorts all faces by area and selects the three biggest ones

wp = (
    wp
    .faces(">Z")
    .sort(lambda face: face.Area())[-3:]
)

Using group and clustering

Select the smallest faces that are within 10 units of each other

wp = (
    wp
    .faces(">Z")
    .group(Cluster(lambda face: face.Area(), tol=10)[0])
)

• ⚠️group() call will not yet select new objects, but it will create a new workplane object. Selection should be done immediatelly after the grouping. Grouping data will be erased by next manipulation of workplane.

• selecting a range of groups ([0:2]) works as expected

• Cluster() defaults to a tolerance of 1e-4

Using last to select newly created faces

A call to .last(everything=False) attempts to select newly created faces. When everything = False it will only select faces that share all their edges with other new faces. In other words: probably the face you'd want to focus on after some operation like extrude, cut or revolve will be selected.

Supplying everything = True will select all faces that are new.

from cq_filter import Workplane

wp = (
    Workplane()
    .rect(5, 5)
    .extrude(2)
    .last()
    .workplane()
)

• ⚠️ last will not select faces that were modified

Usage

You may want to create your own workplane class if you have multiple mixins

from cq_filter import CQFilterMixin

class Workplane(CQFilterMixin, cq.Workplane):
   pass

If you don't have multiple mixins, then the above class can also be directly imported

from cq_filter import Workplane