Is Direct Modeling Really Better at Capturing Design Intent?

CAD industry analyst Chad Jackson struck a chord with readers of this blog recently when he declared that “Direct modeling is better at capturing design intent.”

At last count, the blog post had generated 220 likes on Facebook, so I think it’s safe to say that many designers agree with Jackson’s assertion that when it comes to capturing design intent, direct modeling is the clear winner over parametric modeling.

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To sum up, Jackson said the main reason for his finding is that with direct modeling you don’t need to define nearly as many dimensions as you do with parametric modeling. And this means that engineers can only create the dimensional controls that truly represent their design intent.

Jackson’s blog reminded me of a couple of other blog posts you might find interesting. They were written awhile back by PTC’s Paul Hamilton. The first blog takes a look at what Hamilton calls “Parametric Direct Modeling” and the second delves into the topic a bit further by comparing “History-Based Modeling and Direct Editing.”

Hamilton makes the point that many vendors today — including PTC with its Flexible Modeling Extension (FMX) — are offering direct modeling capability within their parametric portfolios.

“Direct editing is being introduced into history-based CAD systems now to simply provide another option in history-based modeling for the editing of 3D models,” Hamilton writes. “With good direct editing we can be somewhat less dependent on a well-structured feature tree.”

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Hamilton goes on to say that some parametric history-based purists consider direct editing within a history-base CAD tool to be risky.

“Perhaps they are concerned that it provides a way to ‘corrupt’ the design intent,” the blog reads. “I find this a little strange in that if in fact the design intent (feature structure and definition) is already pure and perfect, there would certainly be no need for direct editing. Unfortunately this is rarely the case.”

Which approach do you think is best at capturing design intent? Direct or parametric? And do you think that the combination of direct and parametric modeling tools is a risky proposition? I’d love to know your stance on these matters so please post your comments here.

For more on direct and parametric modeling, be sure to download this free 30-day trial version of PTC Creo Parametric with PTC Creo FMX.

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One Comment

  1. FORTNER
    Posted May 4, 2014 at 4:22 am | Permalink

    Is the designer sure of such design intent will drive him directly from requirement to achievement, one straight way?
    More often design is a sum or a combination of intents coming not just from designers, but also from marketing, sales, manufacturing, after-sales, etc. And these contributions may arise soon or later. The problem comes from the “later” design intents coming up. Some may have serious impacts on the current existing design intent, requiring a lot of rework that could make it more difficult to understand later on, when modification time will come.
    Direct editing appears to me more “agile” to face different “later”, unexpected design intents to complete as soon as possible. Is it a must to read clear design intent within a model? Product design intent is not just made of geometry parameters; additional non CAD information is related, and here is the crucial role of PLM.

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