Radius selector

[marcus7070]

I think there is a need for a radius selector. All of CQ's current selectors work of the centre of an object or the bounding box. So if you have the following shape for example:

part = (
    cq
    .Workplane()
    .circle(10)
    .extrude(10)
    .faces(">Z")
    .workplane()
    .hole(10)
)

and you want to fillet just the outer edges and not the inner, the only selector that you can use is some ugly combination of bounding boxes.

A radius selector in the style of DirectionNthSelector would be a good addition IMHO.

[marcus7070]

I think there is a potential method to extract radii.

I can get the radius of the circles from the above code with:

objs = part.faces(">Z").edges("%CIRCLE").vals()
for obj in objs:
    print(obj._geomAdaptor().Circle().Radius())

I don't know enough about OCCT to know if this is the appropriate method, but ignorance is bliss so I'm happy to plow ahead and write a selector (and a bunch of tests for it) based off this method.

[jmwright]

I've run into the same thing before when selecting circles and just ended up using a box selector. It would be nice to have a shortcut for it.

This is tangentially related to a discussion on Discord last week on selecting a circular edge by edge length. It seems like that would be complementary to this for when you're not dealing with a whole circle. You can calculate the edge length, and then select using a length tolerance.

Below is the code that I put together, but as Adam rightly pointed out at the time, I went the long way around to get the length of the edge.

import cadquery as cq
from OCP.GCPnts import GCPnts_AbscissaPoint
from OCP.BRepAdaptor import BRepAdaptor_Curve

# All based on existing source code until next comment
class LengthSelector(cq.Selector):
    new_obj_list = []

    def __init__(self, length):
        self.length = length

    def filter(self, objectList):
        for obj in objectList:
            curve = BRepAdaptor_Curve(obj.wrapped)
            edge_len = GCPnts_AbscissaPoint.Length_s(curve)
            
            # Only return edges that meet our requirements
            tol = 0.2
            if edge_len > self.length - tol and edge_len < self.length + tol: 
                log(edge_len)
                self.new_obj_list.append(obj)
        
        return self.new_obj_list

pts = [(0, 0, 0), (10, 10, 0), (10, 0, 0)]
result = cq.Workplane().polyline(pts).close().extrude(10)
result = result.edges(LengthSelector(14.0)).fillet(1.0)

show_object(result)

And here's what @shimwell ended up with after cleaning up my code.

[michaelgale]

My cqkit library has a RadiusSelector and a DiameterSelector. I love the selector functionality and how easily it is extended. Alternative selectors are the biggest part of the cqkit package for good reason!
Example:

    r = (
        cq.Workplane("XY")
        .circle(2)
        .workplane(offset=3, centerOption="ProjectedOrigin")
        .circle(3)
        .loft()
    )
    rs = RadiusSelector(2)
    assert r.edges(rs).size() == 1
    rs = RadiusSelector(3)
    assert r.edges(rs).size() == 1

[shimwell]

Planning to make good use of that length selector and made an area selector in the same way that you taught me @jmwright . Thanks for your help. A radius selector sounds like a great idea.

[adam-urbanczyk]

@marcus7070 do you want to backport the selector from cqkit then?

[marcus7070]

Yes, I'll do that in the next few days. I see @michaelgale also used the _geomAdaptor, so that gives me a lot more confidence.

[adam-urbanczyk]

OK, _geomAdaptor is indeed the way to go.