Padding

This example demonstrates the qtcad.builder.Builder.pad_group operation.

Initialization

from qtcad.builder import Builder
from qtcad.builder import Mask, Polygon

2D Padding

The pad_group works on 2D and 3D groups. We will now demonstrate the former. We use circular shapes here as they better demonstrate the effects of growth parameters on curved surfaces.

from qtcad.builder import Circle

circle_1 = Circle(name="gate_1").centered().translated(-2, 0)
circle_2 = Circle(name="gate_2").centered().translated(2, 0)

gate_mask_2d = Mask("gates")
gate_mask_2d.add_shape(circle_1)
gate_mask_2d.add_shape(circle_2)

builder_2d = (
    Builder(name="padding demo 2d")
    .set_mesh_size(10)
    .add_mask(gate_mask_2d)
    .group_from_mask()
    .add_surface()
)

INFO     Creating a surface from shape 0 with name      _builder.py:2599
         'gates' from mask 'gates' at z=0
INFO     Creating new physical group of dimension 2     _builder.py:2679
         with name 'gates'
INFO     Creating a surface from shape 1 with name      _builder.py:2599
         'gates' from mask 'gates' at z=0

At this point we have two circular 2D “gates”

builder_2d.view(
    surfaces=True,
    volume_labels=False,
    save="figs/before_padding_2d.svg",
)

           INFO     Saving figure                                  _builder.py:1994

<qtcad.builder.builder.Builder object at 0x7ff520ffd310>

Now we add padding around the 2D gates. The grow_accuracy and grow_complexity arguments can be used to control the algorithm used to grow the shapes.

Builder.pad_group(group: str | list[str] | Callable[[PhysicalGroup], bool], thickness: float, padding_suffix: str = '_padding', noclip: bool = False, grow_complexity: float = 10.0, grow_accuracy: int = 100, min_curve_nodes: int = 20) → Self

[🏗️ Operation] Add a padding layer of thickness around the volumes in volume group with name group_name. The newly created padding volume will be named group_name + padding_suffix and clipped horizontally by the currently selected shapes unless noclip is True.

Parameters:

• group – The group(s) to pad. See get_group for details on the allowed types.

• thickness – The padding thickness.

• padding_suffix – Suffix to append to the group name for the new volume.

• noclip – If True, no horizontal clipping will occur. Default is False.

• grow_complexity – See grow().

• grow_accuracy – See grow().

• min_curve_nodes – See grow().

First, we can pad both shapes at once by referencing the mask group:

builder_2d.pad_group(
    "gates",
    2,
    noclip=True,
    grow_complexity=5,
)

[14:50:35] INFO     Padding Physical Group 'gates' of dimension 2   _builder.py:486
                    with a layer of thickness 2
           INFO     Growing surface (2, 3)...                      _builder.py:3674
           INFO     Growing surface (2, 4)...                      _builder.py:3674
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gates_padding'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320
           INFO     Restored z coordinate to 0                     _builder.py:3721

<qtcad.builder.builder.Builder object at 0x7ff520ffd310>

Viewing the result for padding both shapes at once

builder_2d.view(
    surfaces=True,
    volume_labels=False,
    save="figs/final_2d_grouped.svg",
)

           INFO     Saving figure                                  _builder.py:1994

<qtcad.builder.builder.Builder object at 0x7ff520ffd310>

Padding Shapes Individually

We will now pad the shapes individually to demonstrate the effect of the control parameters.

• Higher grow_complexity leads to more complex grown shapes (more facets), but increases runtime (increasing the complexity of the resulting CAD model).

• Higher grow_accuracy increases the precision of the grown shapes, also at the cost of runtime.

We demonstrate this by comparing three circles:

circle_1 = Circle(name="gate_1").centered().translated(-4, 0)
circle_2 = Circle(name="gate_2").centered().translated(0, 0)
circle_3 = Circle(name="gate_3").centered().translated(4, 0)

gate_mask_indiv = Mask("gates_indiv")
gate_mask_indiv.add_shape(circle_1)
gate_mask_indiv.add_shape(circle_2)
gate_mask_indiv.add_shape(circle_3)

builder_indiv = Builder(name="padding demo 2d individual")
(builder_indiv.add_mask(gate_mask_indiv).group_from_shape().add_surface())

[14:50:36] INFO     Creating a surface from shape 0 with name      _builder.py:2599
                    'gate_1' from mask 'gates_indiv' at z=0
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1'
           INFO     Creating a surface from shape 1 with name      _builder.py:2599
                    'gate_2' from mask 'gates_indiv' at z=0
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2'
           INFO     Creating a surface from shape 2 with name      _builder.py:2599
                    'gate_3' from mask 'gates_indiv' at z=0
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_3'

<qtcad.builder.builder.Builder object at 0x7ff52105f390>

Now we apply padding with different parameters:

1. gate_1: Low complexity (2) but high accuracy (1000). This results in a coarse, polygonal padding (few facets).

2. gate_2: High complexity (20) but low accuracy (1). This may lead to geometric artifacts or imprecision.

3. gate_3: High complexity (20) and high accuracy (1000). This results in a smooth, accurate circular padding.

(
    builder_indiv.pad_group(
        "gate_1", 1, noclip=True, grow_complexity=0.05, grow_accuracy=1000
    )
    .pad_group("gate_2", 1, noclip=True, grow_complexity=20, grow_accuracy=1)
    .pad_group("gate_3", 1, noclip=True, grow_complexity=20, grow_accuracy=1000)
)

           INFO     Padding Physical Group 'gate_1' of dimension 2  _builder.py:486
                    with a layer of thickness 1
           INFO     Growing surface (2, 4)...                      _builder.py:3674
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_padding'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320
           INFO     Restored z coordinate to 0                     _builder.py:3721
           INFO     Padding Physical Group 'gate_2' of dimension 2  _builder.py:486
                    with a layer of thickness 1
           INFO     Growing surface (2, 7)...                      _builder.py:3674
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_padding'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320
           INFO     Restored z coordinate to 0                     _builder.py:3721
           INFO     Padding Physical Group 'gate_3' of dimension 2  _builder.py:486
                    with a layer of thickness 1
           INFO     Growing surface (2, 10)...                     _builder.py:3674
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_3_padding'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320
           INFO     Restored z coordinate to 0                     _builder.py:3721

<qtcad.builder.builder.Builder object at 0x7ff52105f390>

Viewing the result of individual padding

builder_indiv.view(
    surfaces=True, volume_labels=False, save="figs/final_2d_individual.svg"
)

           INFO     Saving figure                                  _builder.py:1994

<qtcad.builder.builder.Builder object at 0x7ff52105f390>

3D Padding

Setting up the shapes

Here we define the device substrate shape (a simple box)…

substrate = Polygon.box(10, 10, name="substrate").centered()

… and the two “gates”

gate_1 = Polygon.box(10, 1, name="gate_1").centered().translated(0, -2)
gate_2 = gate_1.translated(0, 4).named("gate_2")

Finally we assemble them into masks

box_mask = Mask("substrate")
box_mask.add_shape(substrate)
gate_mask = Mask("gates")
gate_mask.add_shape(gate_1)
gate_mask.add_shape(gate_2)

Polygon(name='gate_2', id=1, hull=[(-5, 1.5), (-5, 2.5), (5, 2.5), (5, 1.5)], holes=[])

Generating the geometry

builder = Builder(name="padding demo")

(
    builder.set_mesh_size(10)
    .add_mask(box_mask)
    .add_mask(gate_mask)
    .group_from_shape()
    .use_mask("substrate")
    .use_shape("substrate")
    .extrude(3)
    .use_mask("gates")
    .extrude(0.4)
)

[14:50:38] INFO     Using mask 'substrate' (implicitly selecting    _builder.py:827
                    shapes [Polygon 0 'substrate'])
           INFO     Selected shapes: [Polygon 0 'substrate']        _builder.py:880
           INFO     Extruding shape 0 from mask 'substrate' with   _builder.py:2895
                    name 'substrate' by 3 at z=0
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'substrate_bottom'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'substrate_side'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'substrate_top'
           INFO     Creating new physical group of dimension 3     _builder.py:2679
                    with name 'substrate'
           INFO     Setting z-coordinate to 3                       _builder.py:929
           INFO     Using mask 'gates' (implicitly selecting shapes _builder.py:827
                    [Polygon 0 'substrate'])
           INFO     Extruding shape 0 from mask 'gates' with name  _builder.py:2895
                    'gate_1' by 0.4 at z=3
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_bottom'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_side'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_top'
           INFO     Creating new physical group of dimension 3     _builder.py:2679
                    with name 'gate_1'
           INFO     Extruding shape 1 from mask 'gates' with name  _builder.py:2895
                    'gate_2' by 0.4 at z=3
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_bottom'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_side'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_top'
           INFO     Creating new physical group of dimension 3     _builder.py:2679
                    with name 'gate_2'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320
           INFO     Setting z-coordinate to 3.4                     _builder.py:929

<qtcad.builder.builder.Builder object at 0x7ff52105fc50>

At this point we have two “gates” on top of a “substrate”

builder.view(
    surfaces=False,
    volume_labels=True,
    angles=(-45, 0, 45),
    save="figs/before_padding.svg",
)

           INFO     Saving figure                                  _builder.py:1994

<qtcad.builder.builder.Builder object at 0x7ff52105fc50>

Now we add padding around those gates. The first padding will not be clipped, whereas the padding around the second gate will be clipped by the substrate shape we selected beforehand.

(
    builder.use_mask("substrate")
    .use_shape("substrate")
    .pad_group("gate_1", 0.6, noclip=False)
    .pad_group("gate_2", 0.6, noclip=True)
)

           INFO     Using mask 'substrate' (implicitly selecting    _builder.py:827
                    shapes [Polygon 0 'substrate'])
           INFO     Selected shapes: [Polygon 0 'substrate']        _builder.py:880
           INFO     Padding Physical Group 'gate_1' of dimension 3  _builder.py:486
                    with a layer of thickness 0.6 (clipping with
                    shapes with shapes: [Polygon 0 'substrate'])
           INFO     Growing volume (3, 5)...                       _builder.py:3464
[14:50:39] INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_padding_bottom'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_padding_side'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_1_padding_top'
           INFO     Creating new physical group of dimension 3     _builder.py:2679
                    with name 'gate_1_padding'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320
           INFO     Padding Physical Group 'gate_2' of dimension 3  _builder.py:486
                    with a layer of thickness 0.6
           INFO     Growing volume (3, 10)...                      _builder.py:3464
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_padding_bottom'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_padding_side'
           INFO     Creating new physical group of dimension 2     _builder.py:2679
                    with name 'gate_2_padding_top'
           INFO     Creating new physical group of dimension 3     _builder.py:2679
                    with name 'gate_2_padding'
           INFO     Identifying potential intersections...        fragmenter.py:290
           INFO     Fragmenting...                                fragmenter.py:320

<qtcad.builder.builder.Builder object at 0x7ff52105fc50>

Viewing the result

builder.view(surfaces=False, angles=(-45, 0, 45), save="figs/final.svg")

           INFO     Saving figure                                  _builder.py:1994

<qtcad.builder.builder.Builder object at 0x7ff52105fc50>

Hiding the padding volume

builder.view(
    True,
    groups=["gate_1", "gate_2", "substrate"],
    surfaces=True,
    volume_labels=True,
    angles=(-90, 0, 90),
    orthographic=True,
    save="figs/padding_removed.svg",
)

[14:50:40] INFO     Saving figure                                  _builder.py:1994

<qtcad.builder.builder.Builder object at 0x7ff52105fc50>