Who’s interested in a brand new, from-scratch boundary representation (BREP) kernel? How about one that has no topological naming problem, a web-native parametric CAD front end to play with, and has CAD-type operations making friends with triangle meshes? If you’re intrigued, check out [mmiscool]’s BREP project.

Functioning (let alone feature-filled, or efficient) CAD systems are not a software project we see a whole lot of. Ones that represent models as genuine BREP structures but cleverly use mesh-based operations where it makes sense? Even less so.

In theory, CAD programs are simple: allow a user to define features, keep track of what they are and how they relate to one another, and perform operations on them as requested. In practice, it’s significant work. Chains of operations and dependencies easily become complex, volatile things and there is really no room for error.

Read [Arya Voronova]’s best practices for using FreeCAD to get a few hints as to what goes on behind the scenes in a modern CAD program, and the kinds of challenges the back end has to deal with, like the topological naming problem (TNP). A problem [mmiscool]’s implementation completely avoids, by the way.

There is a live demo at BREP.io which acts as a playground for the state of the project. You can get started by clicking the + button towards the top on the left panel to add features and operations to the history (like add a cube, then add chamfers or fillets, or extrude a face, and so on).

[mmiscool] points out that all computation is done client-side; even complex operations like fillets, lofts, and multi-body booleans execute directly in the browser with no need to be offloaded to a back end. BREP’s development is being documented on Hackaday.io and there is a video embedded below that gives an overview. Why don’t you give it a spin?

We love and hate OpenSCAD. As programmers, we like describing objects we want to 3D print or otherwise model. As programmers, we hate all the strange things about OpenSCAD that make it not like a normal programming language. Maybe µCAD (or Microcad) is the answer. This new entry in the field lets you build things programmatically and is written in Rust.

In fact, the only way to get it right now is to build it from source using cargo. Assuming you already have Rust, that’s not hard. Simply enter: cargo install microcad. If you don’t already have Rust, well, then that’s a problem. However, we did try to build it, and despite having the native library libmanifold available, Rust couldn’t find it. You might have better luck.

You can get a feel for the language by going through one of the tutorials, like the one for building a LEGO-like shape. Here’s a bit of code from that tutorial:

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)
.align()
}

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;
}

There are proper functions, support for 2D sketches and 3D objects, and even a VSCode extension.

Will you try it? If we can get it to build, we will. Meanwhile, there’s always OpenSCAD. Even TinkerCAD can do some parametric modeling.