Working with Polychannels

Prev: Part 6: Parametric Design

A polychannel is a high-level channel shape built from a sequence of simple shapes that are automatically hulled together. It is the easiest way to make smooth, variable-width channels.

Polychannels are powerful because they let you:

Blend shapes (cube → rounded cube → sphere)
Change cross‑section along the path
Add rounded bends or smooth Bézier curves
Mix absolute and relative positioning
Build routing paths without manual boolean operations

Step 1 — Import the polychannel classes

from pymfcad import Polychannel, PolychannelShape, BezierCurveShape

Step 2 — Build a simple polychannel

Each PolychannelShape defines a point in the path. The channel is formed by hulling between these shapes.

shapes = [
    PolychannelShape(
        shape_type="cube",
        position=(0, 0, 0),
        size=(0, 10, 10),
    ),
    PolychannelShape(
        shape_type="cube",
        position=(20, 0, 0),
        size=(10, 10, 10),
    ),
    PolychannelShape(
        shape_type="cube",
        position=(0, 20, 0),
        size=(10, 10, 10),
        corner_radius=5,
    ),
    PolychannelShape(
        shape_type="cube",
        position=(20, 20, 0),
        size=(10, 10, 10),
        corner_radius=0,
    ),
]

channel = Polychannel(shapes)

Checkpoint: You now have a smooth channel that turns a corner.

Step 3 — Add the polychannel to a component

from pymfcad import Component, Color, Cube, Polychannel, PolychannelShape

component = Component(
    size=(100, 100, 20), position=(0, 0, 0), px_size=0.0076, layer_size=0.01
)
component.add_label("default", Color.from_rgba((0, 255, 0, 255)))
component.add_label("bulk", Color.from_name("aqua", 127))

channel = [
    PolychannelShape(
        shape_type="cube",
        position=(0, 0, 0),
        size=(0, 10, 10),
    ),
    PolychannelShape(
        shape_type="cube",
        position=(20, 0, 0),
        size=(10, 10, 10),
    ),
    PolychannelShape(
        shape_type="cube",
        position=(0, 20, 0),
        size=(10, 10, 10),
        corner_radius=5,
    ),
    PolychannelShape(
        shape_type="cube",
        position=(20, 20, 0),
        size=(10, 10, 10),
        corner_radius=0,
    ),
]
component.add_void("polychannel_void", channel, label="default")

bulk_cube = Cube((100, 100, 20))
component.add_bulk("bulk", bulk_cube, label="bulk")

component.preview()
component.render("my_first_component.glb")

Basic shapes

Step 4 — Add a Bézier curve (optional)

Use BezierCurveShape when you want a smooth, curved segment.

from pymfcad import Component, Color, Cube, Polychannel, PolychannelShape, BezierCurveShape

component = Component(
    size=(100, 100, 20), position=(0, 0, 0), px_size=0.0076, layer_size=0.01
)
component.add_label("default", Color.from_rgba((0, 255, 0, 255)))
component.add_label("bulk", Color.from_name("aqua", 127))

channel = Polychannel(
    [
        PolychannelShape(shape_type="cube", position=(0, 0, 0), size=(10, 10, 10)),
        PolychannelShape(shape_type="cube", position=(20, 0, 0), size=(10, 10, 10)),
        BezierCurveShape(
            control_points=[(50, 0, 0), (100, -100, 0), (200, 100, 0), (50, 0, 0)],
            bezier_segments=25,
            position=(50, 50, 0),
            size=(10, 10, 10),
            shape_type="rounded_cube",
            rounded_cube_radius=(3, 3, 3),
        ),
        PolychannelShape(
            shape_type="cube",
            position=(0, 50, 0),
            size=(10, 10, 10),
            corner_radius=0,
        ),
    ]
)
component.add_void("polychannel_void", channel, label="default")

bulk_cube = Cube((100, 100, 20))
component.add_bulk("bulk", bulk_cube, label="bulk")

component.preview()
component.render("my_first_component.glb")

Basic shapes

Tips

The first shape cannot be a Bézier curve.
The first shape must define shape_type, position, and size.
The last shape cannot have a non‑zero corner_radius.
corner_radius applies at the bend point and stays active until reset to 0.
absolute_position=False means each position is relative to the previous shape.
rounded_cube requires rounded_cube_radius.
All positions and sizes are in pixels/layers.
You can mix cubes, spheres, and rounded cubes in the same channel.

Capabilities and how to use them

Variable width/height: change size from one shape to the next.
Rounded bends: set corner_radius on the bend point, then reset to 0 later.
Smooth curves: insert BezierCurveShape with control_points.
Shape blending: mix cube, sphere, and rounded_cube to change channel profile.
Relative vs absolute positioning: keep absolute_position=False for incremental steps, or set it to True for explicit coordinates.

Now that you have a basic understanding of polychannels, you can move on to adding components into your device.