Parametric vs. Direct Modeling: Which Side Are You On?
by Mark Brunelli | April 07, 2017 | CAD Software Blog | PTC
Engineers have long debated the virtues of parametric versus direct modeling. Some like the freedom and flexibility of direct modeling, while others prefer the feature definition and dimension control capabilities associated with parametric systems.
Direct modeling empowers you to define and capture geometry quickly, without spending time worrying about features, constraints, and original design intent. With parametric modeling, you capture design intent using features and constraints, and this allows users to automate repetitive changes, such as those found in families of product parts.
So which is better, direct or parametric? The answer is “all of the above.” While each has its benefits, the best CAD software uses both approaches to modeling. Manufacturers that integrate direct modeling into their parametric environment report greater speed, quality, and focus on innovation that helps them stay ahead of the competition.
But before we talk about that, let’s weigh some of the pros and cons of direct and parametric modeling.
Parametric Modeling: Pros and cons
Parametric Modeling technologies are a great fit for design tasks that involve exacting requirements and manufacturing criteria. For example, organizations often turn to parametric when making families of products that include slight variations on a core design, because the designer will need to create design intent between dimensions, parts and assemblies. This supports designs that will need to be modified or iterated on a regular basis. It also creates models with individual features that can be modified or changed — such as holes and chamfers — that are captured in a ‘model tree.’
Champions of parametric modeling enjoy benefits that include:
- Automatic updates to the model if changes are made to the design.
- The ability to easily capture design intent, which makes it easier to define how the model should behave when something is changed.
- Easy definition and automatic creation of families of parts.
- Excellent integration with manufacturing processes, resulting in a decrease in production time.
But parametric technology is not without its drawbacks. Some of the cons associated with parametric modeling include the following:
- During concept design, parametric 3D CAD may be overkill for designers trying to investigate as many 3D concepts of an idea as quickly as possible.
- Parametric models take more time to update when unexpected design changes are needed.
Direct modeling: Pros and consDirect modeling creates geometry rather than features so it supports that conceptual effort where the designer doesn’t want to be tied down with features and their inter-dependencies and the impact that making a change might have.
Ask the expert: Monica Schnitger weighs in“Each approach, parametric or direct, has its uses and perhaps the perfect CAD strategy incorporates both,” CAD software industry analyst Monica Schnitger, president and founder of The Schnitger Corporation, has said.
Schnitger cites these examples:
“It might make sense to use direct modeling during conceptual thinking, when you need to quickly manipulate the design and don’t want to be slowed down by working within pre-defined rules,” Schnitger added. “During detailed design, when most of the free thinking and exploring is finished, it might be reasonable to use parametric design to ensure that future iterations don’t violate the original concept.”
Conclusion: The best systems use both parametric and direct
The bottom line is that you need both approaches to deal with the complexity of today’s product designs. We've seen examples of companies iPhone case makers, to digital imaging companies and printed circuit board manufacturers in using both approaches. Each uses Creo, a full-featured modeling tool, including parametric and direct modeling capabilities in one environment, working on one model. You can read more about the benefits of each approach in part 2 of this series: Best Approach to 3D Modeling: Parametric, Direct, or All of the Above.
Find out more about Creo
Creo makes the switch from parametric to direct modeling (and back again) easy. But that’s just one reason to try Creo, the industry’s leading 3D CAD software. To find out more, download our free eBook, Top 7 Reasons to Design with Creo.
Ed. This post was published previously. It has been updated with newer links and information.