Direct Modeling vs Parametric Modeling: Which Is More Effective?

Direct Modeling vs Parametric Modeling

The 1987 debut of Pro/ENGINEER, now PTC Creo, marked a pivotal moment in the history of computer-aided design (CAD), since it introduced the CAD industry to history-based parametric modelling. Since then, practically every prominent CAD tool, including SOLIDWORKS, Autodesk Inventor, Creo Parametric, CATIA, NX, and Onshape, has used the parametric paradigm. 

Direct modelling is the appropriate design method for some design engineers because of its openness and flexibility. Others, on the other hand, appreciate the level of control that comes with a parametric approach.

For many, the benefit of direct modelling is the ability to swiftly capture and record new geometry without the limits that come with parametric modelling. Users can record comprehensive design intent with features and limitations that make it possible to automate repetitive modifications using parametric modelling technology, on the other hand.

In summary, parametric design entails engineers’ piece-by-piece constructing a 3D geometry. 2D sketches are converted into 3D features, with constraints and relationships imposed as needed to match the designer’s intent. However, because each stage builds on the one before it, parametric design can demand meticulous planning.

What is Parametric Modelling?

Parametric modelling, often known as history-based modelling, is a systematic engineering technique. This is because it keeps track of the model’s features, and as new ones are introduced, they are catalogued in a list called a feature tree, which makes them easy to update. Each feature is created by manually entering dimensions, ensuring that every measurement and angle is precise.

The features are also regulated by parameters set by the engineer who created the model. This allows the engineer to keep design intent while constructing and altering the model because any changes made will follow the defined parameters that inform the model how to function.

Pros and Cons of Parametric Modelling

Pros – When it comes to design activities that demand precise specifications and production standards, parametric modelling is a wonderful technique. This could include situations where a company produces a product line or family of items with only slight differences. The designer can use parametric modelling to do the following:

  • Every component is regulated by dimensions, enabling for exact adjustments and alterations.
  • Feature tree is the list that keeps track of each feature is always accessible and maintains a step-by-step construction trail.
  • Changes are automatically reflected in the visual model if the proportions of a feature are changed. Identical features can be modified at the same time.
  • The parameters prevent the model from deviating from the original design goal. These algorithms tell the features how to respond to changes in the model’s other sections.
  • Excellent integration with industrial processes, resulting in a reduction in production time.

Cons – The main limitations that are associated with parametric modelling are:

  • Making multiple model iterations via parametric modelling when brainstorming design ideas is typically tiresome and stifles the creative process.
  • When a change is made to the model, the program updates it by resolving each feature in the feature tree in the linear order. The features in the list are linked because they build on each other. Certain changes earlier in the feature tree may break the model as it tries to resolve features farther down the tree if the engineer is not attentive. Late-stage design adjustments can be difficult as a result of this.
  • The feature tree’s list grows bigger as additional features are added. This can take a long time and a lot of energy for the computer to process.
  • As there are so many CAD applications in the market, sharing the model as suite-specific CAD is problematic. Converting the file to generic CAD makes it easier to exchange it between computers, but it removes the feature tree from the file, making further editing more difficult.

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When to use Parametric Modelling?

Parametric modelling works best for activities that require precise dimensions to be generated or met in order for production to continue. Once the part’s concept design has been selected, this is usually done during the engineering phase of production. It’s particularly helpful when a full list of characteristics is required, such as for parts that need to be updated frequently or belong to a family of goods that must share some features.

What is Direct Modeling?

Direct modelling is a method that offers a lot of freedom and flexibility. Direct modelling is a history-free method, which means it does not preserve a log of features or edits like parametric modelling does. There are no parameters defined, therefore features are not linked.

Rather, any geometrical element of the model’s face can be tugged, pushed, or otherwise moved straight into the desired location by the designer. A sculptor’s work with modelling clay can be compared to this type of model. As the project advances, the design intent is defined.

Pros and Cons of Direct Modelling

Pros – Direct modelling develops geometry rather than features. This is perfect for concept design work, as designers want to be able to experiment with a variety of concepts without feeling constrained. It’s all about speed and agility in the design process with a direct modelling approach. 

  • Flexibility – Because the features are not interconnected, modifications can be performed without disrupting the model. This also enables significant adjustments to be made at any time during the process.
  • Agility – Rather than inputting individual dimensions, making direct modifications speeds up the procedure. This allows the designer to quickly and simply experiment with a variety of design options.
  • Versatility — Because this modelling approach does not maintain a feature tree, it may operate with generic CAD models (STEP/IGES files).

Cons – So, what are the disadvantages? Direct modelling, in contrast to parametric modelling, has following problems:

  • When altering the geometry in a direct model, dimensions are displayed, but there is no history of these measurements. If you’re seeking for actual measures rather than a notion, this makes them more difficult to track and edit.
  • Identical characteristics, such as holes, can be changed at the same time with parametric modelling. Direct modelling, on the other hand, does not draw relationships between things, thus if there are similar features, they must be modified separately.
  • It is easy to deviate from the design intent because no parameters are used to specify the design intent and make the model react to changes.
  • Design automation is minimal to non-existent.

When to use Direct Modelling?

The direct modelling method is excellent for activities that require flexibility and speed, such as concept design and rapid prototyping. It can also be useful when developing a one-off part, one with a limited life cycle, or one that will go through several design revisions. In many of those cases, speed is more helpful than parameter control, which will save you time and money while creating your model.

Direct Modeling vs Parametric Modeling- Which Approach Is More Effective?

Which modelling method is ideal for you is primarily determined by the model’s intended purpose and present stage. However, a fair mix of both is advised in general because each will help you with a distinct aspect of the modelling process. Both modelling approaches can produce the same CAD outcome, making data transfer between a parametric modelling program and a direct modelling program simple, however the parametric modelling feature tree will be lost in the process.

In essence, the advantages and disadvantages of direct and parametric modelling indicate that a hybrid method is the best option for product design. It means being able to benefit from the advantages of both approaches without being constrained by their drawbacks.

INDOVANCE Inc is a trusted and specialized CAD outsourcing partner catering to the design and drafting needs of the AEC industry since 2003. Our professionals develop a comprehensive model using full-featured modelling tools that combine parametric and direct modelling capabilities in a unified environment.

For more queries regarding any of the above-mentioned topics, feel free to connect with us on our website www.indovance.com or contact us on +1-919-238-4044.