Adding two closed wires to workplane then do offset2D(), resulting in one wire broken

[garywill]

To Reproduce

import cadquery as cq
import math
OP = cq.Vector(0, 0, 0)
X = cq.Vector(1, 0, 0)
Y = cq.Vector(0, 1, 0)
Z = cq.Vector(0, 0, 1)

wr_elp = cq.Wire.makeEllipse(15, 16, OP, Z, X)
wr_circ =cq.Wire.makeCircle(16, OP, Z)

sld_lofted = (
    cq.Workplane()
    .add(wr_elp)
    .toPending()
    .add(wr_circ.moved(0, 0, 30))
    .toPending()
    .loft()
)
# show_object(sld_lofted)

wr_sectioned = (
    cq.Workplane(origin=(0, 0, 5) )
    .add(sld_lofted)
    .section()
    .wires()[0]
)
# show_object(wr_sectioned)

two_ring_wires = (
    cq.Workplane(origin=(0, 0, 5))

    # ring1
    .add(wr_sectioned)
    .toPending()
    .offset2D(5)

    # ring2
    .add(wr_sectioned)
    .toPending()
    .offset2D(-3)

    #.extrude(10)
)
show_object(two_ring_wires)

Only when two wires are in the workplane, this bug happends. If comment out one of ring1/ring2, you'll get a closed wire.

Environment

OS: Linux
Python 3.11

CadQuery installed by pip install cadquery

Was CadQuery installed using Conda?: no

Using:

pip_list.txt

[lorenzncode]

Here is a simplified MRE.

from cadquery.func import *

# r1, r2 = 16, 15
r1, r2 = 20, 15

e1 = ellipse(r1, r2).moved(rz=90)
# e1 = circle(r1)  # does not reproduce issue

e2 = circle(r1).moved(z=30)

res_loft = loft(e1, e2, cap=True)

wi1 = intersect(res_loft, plane().moved(z=5)).wires()
wi2 = wire(wi1.offset2D(5))
wi3 = wire(wi2.offset2D(-3))
wi3b = wire(wi1.offset2D(2))  # no issue


from cadquery.vis import show

wi3_list = wi2.offset2D(-3)
print(wi3_list)
show(wi3_list, width=600, height=600, roll=0, elevation=0)

It looks like a CAD kernel issue. Replacing edge e1 with circle does not reproduce the issue (or sampling and recreating the wire as in workaround below).

In the original example I think you want to offset the first wire by +5 and -3 rather than by +5 and effectively +2. I did not find an issue with that case.

from cadquery.func import *

r1, r2 = 16, 15
# r1, r2 = 20, 15

e1 = ellipse(r1, r2).moved(rz=90)
e2 = circle(r1).moved(z=30)

res_loft = loft(e1, e2, cap=True)

wi1 = intersect(res_loft, plane().moved(z=5)).wires()
wi2 = Wire.combine(wi1.offset2D(5)).pop()
wi3 = Wire.combine(wi1.offset2D(-3)).pop()

f1 = face(wi2, wi3)
res = extrude(f1, (0, 0, 10))

If the offset is applied as in the MRE, a workaround could be to sample and recreate the wire from the intersection.

from cadquery.func import *

# r1, r2 = 16, 15
r1, r2 = 20, 15

e1 = ellipse(r1, r2).moved(rz=90)
e2 = circle(r1).moved(z=30)

res_loft = loft(e1, e2, cap=True)

wi1a = intersect(res_loft, plane().moved(z=5)).wires()
pnts, params = wi1a.sample(20)
wi1 = wire(spline(pnts, periodic=True))

wi2 = wire(wi1.offset2D(5))
wi3 = wire(wi2.offset2D(-3))

f1 = face(wi2, wi3)
res = extrude(f1, (0, 0, 10))