Custom operation

The knobs and struts are created using multiplicity by translate and align operations.

To make placing the elements more generic we will create an operation called grid which arranges elements in a grid which is centered to origin:

use std::ops::*;

const SPACING = 8mm;

op grid(columns: Integer, rows: Integer) {
    @input
        .translate(x = [0..columns] * SPACING, y = [0..rows] * SPACING)
        .center()
}

The grid operation takes rows and columns as parameters.

Operations - as we already know - have not only an output geometry but an input geometry as well. To be able to access those input geometry we need to use the keyword @input. With @input we insert the elements that are given by the caller. In our case that will be a knob or a strut sketch.

We now can rewrite Knobs and Frame sketches by adding rows and columns as parameter and using the grid operation:

use std::geo2d::*;
use std::ops::*;

const SPACING = 8mm;

op grid(columns: Integer, rows: Integer) {
    @input
        .translate(x = [1..columns] * SPACING, y = [1..rows] * SPACING)
        .center()
}

sketch Base(
    columns: Integer,
    rows: Integer,
    width: Length,
    height: Length
) {
    thickness = 1.2mm;
    frame = Frame(width, height, thickness);
    struts = Ring(outer_d = 6.51mm, inner_d = 4.8mm)
        .grid(columns = columns-1, rows = rows-1);
    frame | struts;
}

sketch Knobs(columns: Integer, rows: Integer) {
    Circle(d = 4.8mm)
        .grid(columns, rows);
}

use Rect as Cap;

columns = 4;
rows = 2;
width = columns * SPACING - 0.2mm;
height = rows * SPACING - 0.2mm;

Base(rows, columns, width, height);
Cap(width, height);
Knobs(rows, columns);

Additionally, to the grid operation, we compute the overall width and height in the LegoBrick part, which are:

• width = rows * 8mm - 0.2mm
• height = columns * 8mm - 0.2mm

Now we are ready to write the final part of a LegoBrick.