Create a sketch for the base

Now, we want to turn the construction of the Lego brick base into a reusable, parametric component. In µcad, a reusable, parametric component that produces or transforms a geometry is called workbench.

There are three kinds of workbenches:

• sketches: produce 2D geometry, e.g. Rect.
• parts: produce 3D geometry, e.g. Sphere.
• op: Turn some input geometry into output geometry, e.g. translate, union or subtract.

Definition of our first sketch

Let's encapsulate the construction of the frame into a sketch workbench called Base.

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

sketch Base(width: Length, height: Length, thickness = 1.2mm) {
    frame = Frame(width, height, thickness);
    struts = Ring(outer_d = 6.51mm, inner_d = 4.8mm)
             .translate(x = [-1..1] * 8mm);
    frame | struts;
}

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

If we examine the syntax of the above example, we can see the following things:

• Names of sketches are commonly written in PascalCase, starting with a capital letter.
• The sketch Base has 3 parameters width, height and thickness. Together they are called the building plan of Base.
• width and height have the type Length and no default value, they are required.
• thickness is also of type Length, but implicitly, because we have defined a default value 1.2mm which is a Length of unit mm.
• The body { ... } of Base constructs the actual geometry.
• Base(width = 15.8mm, height = 31.8mm) is a call of the sketch.

And the best part: We don't even need additional value stores for our measures like thickness, width etc. Every measure has a meaningful name in the parameters. This makes the code clearer and changes easier.

An analogy to natural language

In the previous sections, we have been introduced to main concepts of µcad. If we draw an analogy to natural language, we can summarize:

• The workbenches Base, Frame and Circle act like a noun, the subject of the sentence - it's the geometry being described or manipulated.
• The operation translate function like verbs, indicating operations being applied to the geometry.
• The parameters x = 20mm and 45° serve as adverbs, specifying how the operations are carried out.
• Groups {} serve as subclauses.
• Assignments a = Rect(...) are used to give things a unique name: a is a rectangle.

This analogy helps illustrate how the µcad syntax is designed to be both readable and logical, resembling the structure of natural language in a way that makes the code easier to understand.

Now, we have seen all concepts to actually design our Lego brick in 3D.