Cylinder surface incorrect Axis Direction

[redsk]

Hi, I'm implementing some "drilling" for a project of mine and therefore I need to detect holes in parts.

The orientation returned by face.wrapped.TShape().Surface().Axis().Direction().Coord() seems to be correct in one case of the cases (c below) and incorrect in others (a and b).

In fact, for c the direction axis is parallel to x (correct) while for a and b it is parallel to z (wrong).

Why is this so?

import cadquery as cq
from dataclasses import dataclass

@dataclass
class Hole():
    radius: float
    center: cq.cq.VectorLike
    direction: cq.cq.VectorLike

def find_holes(p: cq.Workplane, hole_size, tolerance=0.001):
    holes = []
    for f in p.faces():
        if (f.geomType() == 'CYLINDER'):
            surface = f.wrapped.TShape().Surface()
            radius = surface.Radius()
            if abs(radius - hole_size) < tolerance:
                direction = surface.Axis().Direction().Coord()
                center = f.CenterOfBoundBox()
                holes.append(Hole(radius, center, direction))
    return holes

def get_solid():
    return (
        cq.Workplane("YZ")
        .moveTo(0, 0)
        .lineTo(0, 10)
        .lineTo(10, 10)
        .lineTo(10, 0)
        .close()
        .extrude(2, both=True)
    )

a = (
    get_solid()
    .workplane(2)
    .pushPoints([(5, 5)])
    .hole(2)
)

b = (
    get_solid()
    .pushPoints([(5, 5)])
    .cylinder(4, 1, combine='cut')
)

c = (
    get_solid()
    .pushPoints([(5, 5)])
    .circle(1)
    .cutThruAll()
)

def list_holes(pl):
    holes = find_holes(pl, 1)
    for h in holes:
        print(h)
    
print("holes in a:")
list_holes(a)

print("\nholes in b:")
list_holes(b)

print("\nholes in c:")
list_holes(c)

Output:

holes in a:
Hole(radius=1.0, center=Vector: (0.0, 5.0, 5.0), direction=(0.0, 0.0, -1.0))

holes in b:
Hole(radius=1.0, center=Vector: (0.0, 5.0, 5.0), direction=(0.0, 0.0, 1.0))

holes in c:
Hole(radius=1.0, center=Vector: (0.0, 5.0, 5.0), direction=(-1.0, 0.0, 0.0))

[lorenzncode]

Why is this so?

The shapes also have Location. It looks like this low level code did not consider it.

Try without the low level OCCT.

import cadquery as cq

a = (
    cq.Workplane("YZ")
    .moveTo(0, 0)
    .lineTo(0, 10)
    .lineTo(10, 10)
    .lineTo(10, 0)
    .close()
    .extrude(2, both=True)
)

a = a.workplane(2).pushPoints([(5, 5)]).hole(2)

center_cyl = a.faces("%CYLINDER").val().Center()
edge1 = a.faces("%CYLINDER").edges("%CIRCLE").val()
radius_cyl = edge1.radius()
normal_cyl = edge1.normal()

[redsk]

The shapes also have Location. It looks like this low level code did not consider it.

Try without the low level OCCT.

Mine was just a minimal example, but how do I find the normal and radius in this case?

rod = (
    cq.Workplane("XY")
    .cylinder(30, 10)
    .transformed(rotate=(90, 0, 0))
    .pushPoints([(0, 0)])
    .cylinder(30, 5, combine='cut')
)

Here the edges are not CIRCLE, they are BSPLINE, and they don't have the normal() method.

[adam-urbanczyk]

Your question does not seem to be related to the original question. Likely an x/y problem, maybe start with describing the use case.

I'm guessing that you are actually interested in faces, so:

1. Select the face of interest f=rod.faces(...).val()
2. Use normalAt() for whatever location that is of interest
3. Use _geomAdaptor().Radius() if applicable

[redsk]

Thanks for your answer.

_geomAdaptor().Radius() is what I needed for the radius.

Regarding the normal, I'm not sure how to use normalAt() for this case. Let's say I have this rod

rod = (
    cq.Workplane("XY")
    .cylinder(30, 10)
    .transformed(rotate=(90, 0, 0))
    .pushPoints([(0, 0)])
    .cylinder(30, 5, combine='cut')
)

and I want to find the axis of the "hole" (which in this case, is the y axis).

The face rod.faces("%CYLINDER")[1].val() is highlighted in the figure, I'd like to get the axis of the cylindrical surface, not sure how normalAt() can help me here.

[lorenzncode]

I'd like to get the axis of the cylindrical surface,

You could find it from the seam edge:

rod.faces("%CYLINDER")[1].edges("%LINE").val().tangentAt(0)

[adam-urbanczyk]

This is not an issue anymore, converting to a discussion.