Evan on Engineering Software

A few weeks ago, Siemens PLM announced something they call Synchronous Technology. At the time, I was watching the blogosphere and media, wondering if people actually "got" what Siemens has done.

I found a few bloggers and writers who seemed to get it in a general sense, but not many who actually understood the deep implications.

To understand what Synchronous Technology is, it helps to look back a bit at the history of CAD.

In the late 1980s, PTC took the CAD market by storm with their Pro/E CAD product. They were so successful over time that parametric feature-based modeling, the methodology underlying Pro/E, became the de-facto standard for mechanical CAD.

Parametric feature-based modeling can be incredibly powerful, but it does little to help users deal with dumb or imported models. For this, the essential method is direct editing (sometimes also called explicit modeling. The terms editing and modeling are, in this context, interchangeable.) Implementations of direct editing vary by program, but the basic concept is pretty simple: editing operations are made directly to the boundary representation model. The end result of direct editing is a dumb solid model – one with no parameters or features.

Dumb solid models are quite useful, but they're not all that easy to edit in useful ways, because they lack feature information. A user might look at a dumb model, and be able to recognize features such as holes, pockets, and bosses, but for CAD programs, it's a much bigger challenge.

The general concept of being able to infer feature information on dumb models has been around for a while. Trispectives (now IronCAD) was one of the first to do this, at a basic level, in 1995 or so. More recently, Kubotek, CoCreate and SpaceClaim have taken the concept (and technology) further, allowing users to edit dumb (typically STEP or imported) models with a fluidity and ease unmatched by typical parametric feature-based CAD systems.

Simplifying somewhat, these tools use feature recognition algorithms to identify geometric relationships between elements of a model, and then use a smart set of editing commands to directly modify the surfaces associated with those inferred features. In short, feature recognition plus direct editing .

I personally think that names are important, because they give us a mental schema for recognizing things. I've spent a bit of time talking to industry people (professors, developers, analysts, editors, and such), and there seems to be a consensus that a good name for this type of thing is feature inference modeling.

Now, after that look back at history, the question today is this: What is Synchronous Technology?

The quick answer is that it is a technology that enables something that looks like a combination of feature based modeling and feature inference modeling.  But the quick answer is probably not quite good enough.

The word "synchronous" doesn't refer to a modeling process, but rather refers to what's known as a synchronous solver.

A solver is a computer algorithm that solves a group of mathematical equations. Any CAD program that supports creating or editing features will have a solver buried deeply within its code.

Sequential solvers are the oldest and simplest type. They have the limitation of order dependency. If you drew a four-bar linkage in a sketcher program that used a sequential solver, you'd find that the links had an inherent parent-child relationship. Pushing on the first link would move the last link, but pushing on the last link wouldn't move the first link.

Simultaneous solvers (used in most of today's parametric feature-based modelers) are more advanced. They solve all the equations representing the constraints (including relationships and dimensions) defining a feature simultaneously, as a group. This is computationally more expensive than solving the equations sequentially, but it overcomes the problem of order dependency – at least within a single feature.

Typical parametric feature-based modelers hold the definitions for each of the features in a model in a tree structured list. This list is sometimes called a history tree, as the data in it is listed in the historical order in which the user created the model.

When people talk about history-based CAD software, they're essentially talking about parametric feature-based programs that, in the process of regenerating the boundary representation for a model, recalculate each feature sequentially, as they appear in the history tree. If you've used these type of programs for more than about 5 minutes, you probably understand the problem with this method: a change to a parameter of a feature that's in the early part of the tree can cause features that are later in the tree to fail.

Siemens' synchronous solver overcomes the order dependencies that have plagued history-based CAD programs by solving for the explicit and inferred constraints at the same time. The synchronous solver doesn't use a history tree, but rather holds user-defined constraints in groups associated with the surfaces to which they apply.

The synchronous solver actually does a lot more than a typical simultaneous solver. Were any of the programmers who wrote it to read this blog, they'd probably say I was oversimplifying things. I admit that I am - but for good reason: what's important is what Synchronous Technology does for users, not how it works under the hood.

As far as CAD users are concerned, the result of Synchronous Technology is that they can take an existing model (native or imported), make changes to it with no limitations from the history tree, and add new intelligence (constraints and driving dimensions), again, with no limitations from the history tree.  Easy CAD model reuse, without having to be a CAD genius.

Siemens has started to use the term Design Freedom to describe the capabilities provided by Synchronous Technology. Probably a pretty good term.

There is a lot more to talk about with Synchronous Technology.  I've not even touched on its deeper implications here.  Ultimately, though, I believe this to be a transformative technology -- one that represents an important inflection point in the CAD industry.  If you hear someone say "that's nothing new," don't believe them.  Synchronous Technology is a big deal.

(Nothing I've written here is based on any secret information.  It's all based on published material, and open presentations and conversations at the Siemens PLM analyst & press event.)