Direct Modeling. Seems like every other day there’s another announcement about it from a software provider. Some time ago, Autodesk joined the fray when they developed something called Inventor Fusion in the Autodesk labs. Curious about what exactly it would offer, I hopped on the phone with Rob Cohee, Evangelist for Autodesk Manufacturing (twitter @robcohee) and Garin Gardner, Product Manager for Inventor, to get a little bit better acquainted with it. Here’s what I found and my perspective on it.


Back on February 4th, 2009, Autodesk originally announced their plans to develop and offer a new technology called Inventor Fusion that would be integrated with Inventor (press release). Autodesk then provided two rounds of previews of the technology from Autodesk Labs to enable users to explore the technology and provide feedback through June 2010 (press release). Then in March 2011, Autodesk announced that the Fusion technology would be included at no extra cost as a companion application to Autodesk Alias Design and Alias Automotive, Autodesk Inventor, Autodesk Moldflow, Autodesk Simulation and AutoCAD products (GraphicSpeak blog post).

Capabilities Provided

So what exactly does Fusion do? To start from a Direct Modeling perspective, it does what you would expect. It allows you to take an existing model and manipulate it with direct actions like translate, rotate and the like. It includes translators for other native CAD formats and, like other Direct Modeling technologies, can directly edit imported 3D models using direct manipulation operations. As such, it enables a number of scenarios such as concept design and an editor for simulation model preparation.

What is a little more interesting is the interaction it has with Inventor and the models that are created through the feature-history paradigm. In this specific area, Autodesk has included a set of functionality called change manager. This quote from a press release describes what it can do at a high level.

One of the key new features in Inventor Fusion Technology Preview is the change manager functionality*, which enables users to edit a model in Inventor Fusion and then move it into Autodesk Inventor software, automatically updating the model if the user decides to accept the changes. As a result, users can experience smooth, bidirectional parametric and direct modeling workflows without being forced into one approach or the other.

So what does this do exactly? Well, it enables the following sequence of actions.

  1. You have an existing Inventor model built up with a set of features in a specific order.
  2. You can open that Inventor model in Fusion. Once there you can manipulate the model with direct actions. You can then save that model.
  3. When you open that model in Inventor, the change manager comes up giving you an itemized overview of the manipulations that were made in Fusion. From there, you can choose which changes you’d like to keep and those you would like to disregard.

Why would you need this capability? It is necessary because Inventor and Fusion fundamentally manipulate geometry in two different ways. Inventor relies on the Feature-History approach. Fusion relies on the Direct Modeling approach. And they both need to be able to work on the same model.

Analysis and Commentary

When Autodesk announced they would be including Fusion in just about every suite that the Manufacturing division offers, the rationale was that Fusion would help users transition from 2D to 3D. And I agree that logic holds merit. Diving into the world of features, parameters, and parent-child relationships is like walking off a pretty steep and very high cliff. This step-wise approach can let a user get used to thinking in 3D without all the other stuff. Once they get used to that, they can take the next step into all the complexity and power of full parametric feature-based 3D CAD. I think that scenario works well for a drafter, the person who is front of CAD 80% or more a day, needs to make that transition.

But what about other roles? As you probably know from my past posts, I firmly believe that there are many engineers who will never be experts at any specialized software, include Feature-History 3D CAD. They’re too busy running from the shop floor to the test lab to supplier sites to customers and between various conference rooms to every gain that knowledge and skills. For them, Fusion could be a great fit by reducing the skill and knowledge overhead required of engineers to use 3D. I don’t think this is the part of any official Autodesk strategy. I think they still plan to try to get that engineer to use the full parametric feature-based CAD. But in the end it doesn’t matter too much. Aside the fact that for the engineer to use Fusion, the would need to buy a suite that includes a bunch of other stuff.

What about the change manager? By implementing this capability, I think they are directly taking on an issue that seems to be ignored by many others so far. You see, there’s a fundamental issue here. The use case for using both the Feature-History paradigm and Direct Modeling paradigm legitimately has merit. The problem is that you could easily use Direct Modeling to make a change to a model that violates the definition of an existing feature. Think about it. If you take a revolution and translate and rotate its top face, that geometry can no longer be generated using a revolve action regardless of if it is a feature or not. Autodesk has put in a mechanism to control if that change is propagated when you switch from one paradigm to the other. What happens if you accept a change that invalidates a feature? That’s not exactly clear to me yet. Perhaps it turns into a dumb piece of geometry, almost as if it were imported. Perhaps we’ll eventually find another approach that better handles this feature invalidation use case, but for now, I haven’t heard of a better one.

Conclusions and Questions

As of today, Autodesk is including Fusion, a Direct Modeling technology, as part of many suites. It allows users to directly manipulate geometry instead of using parametrics and features. It also includes a change manager technology to enable Inventor models to be modified by Fusion and vice versa.

I see Fusion easing the transition from 2D to 3D parametric modeling for drafters and CAD Specialists. I also see the Fusion technology being beneficial to engineers, who otherwise wouldn’t touch CAD. I also see the change manager as a ‘best so far’ means of managing Direct Modeling manipulations that invalidate features. But that’s not to say that something better will be introduced in the industry for this use case in the future.

So that’s my take. What’s yours? For those of you using Fusion and Inventor together, what has your experience been? What do you think of the change manager functionality and handling of invalidated features? I’d like to hear from the front lines.

Take care. Talk soon. And thanks for reading.