Sketch caps & knobs

With the knowledge we have gained in the previous chapter, the remaining sections of the brick (Cap and Knobs) can be constructed swiftly.

Cap

The Cap is nothing more than a rectangle. We do not have to define a specific sketch Cap, instead we can use an alias:

// alias Rect as Cap
use std::geo2d::Rect as Cap;

Cap(width = 31.8mm, height = 15.8mm);

std::geo2d::Rect will now also be known as Cap.

Knobs

The knobs of the brick are simple circles with a diameter of 4.8mm. We can easily construct a grid with circles via multiplicity:

std::geo2d::Circle(d = 4.8mm, c = (
        x = ([-1..2] - 0.5) * 8mm, 
        y = ([0..1] - 0.5) * 8mm)
    );

Because ranges can only deal with integers, calculating x and y is a bit tricky here, because x is [-1..2] (which is [-1, 0, 1, 2]) and y is [0..1], we now have no element in the middle anymore. So we have to subtract 0.5 from all the array values before multiplying with 8mm to get a centered result.

To avoid this complication we can use the operation center(). By default, if we do not pass any arguments to operation, it will center the object to origin.

std::geo2d::Circle(d = 4.8mm, c = (
        x = [0..3] * 8mm, 
        y = [0..1] * 8mm)
    ).std::ops::center();

The code looks clearer now.

Tuples

Notice that we have called the std::geo2d::Circle with an additional argument c. c is given as a tuple (x = ..., y = ...). A tuple is a collection of (mostly named) values.

The parameter c of a circle is supposed to be a tuple of type (x: Length, y: Length). By passing an array of Length to the tuple, we are generating a multiplicity, which eventually creates 2*4 circles.

Let's create a sketch for the knobs:

sketch Knobs(diameter = 4.8mm) {
    std::geo2d::Circle(d = 4.8mm, c = (x = [0..3] * 8mm, y = [0..1] * 8mm))
        .std::ops::center();
}

Knobs();

We now have all the sketches we need! Let's move on and bring them together...