This is What 3D Direct Modeling Is

Computer-aided design (CAD) is the use of computers to help create and optimize different designs for various fields. It has over the last few decades led to increased interest in 3D modeling for other fields such as 3D animation and creation of more lifelike and organic models.

3D direct modeling model


3D modeling comes in two main forms: 3D parametric modeling and the newer and increasingly popular 3D direct modeling.

Three-dimensional (3D) direct modeling is a technique where the creator can interact directly with the geometric model on the screen in real-time to change its size shape, delete certain features, or combine different models until they have achieved the 3D model they want.

3D modeling has continued to grow and be put to use both in conjunction with parametric modeling and on its own. Take a look below to see how the two forms of 3D modeling differ and work together.

The Difference Between Parametric and Direct Modeling

Parametric modeling is a way of creating a 3D model in which you create a sketch of the model, give it different parameters and then input those parameters into the code itself, which then renders the 3D image. It is possible to change the 3D model by going in and adjusting the numbers in the system relating to size or curvature. Once you have changed one aspect, the rest of the numbers will adjust to stay within the guidelines or parameters already in the code.

What this means is that if there is a certain aspect of the model that you no longer want as part of the design, it needs to be removed from the code. This can become tricky and may not be possible in the long run.

On the other hand, direct modeling is more flexible, and the different parts of the model are independent of each other. Instead, the creator interacts with the model itself, adjusting it as they see fit. This means they can change the size of one part of the model drastically, and if they do not increase the size of the other parts, they will stay the same size, shape, etc., as before.

As stated, the main difference between parametric and direct modeling is where the edits or adjustments are made (to the parameters in an already established design for parametric or directly to the geometric model itself for direct modeling). This difference leads to a couple of other differences, such as the following:

Parametric Modeling

Direct Modeling

Has to follow already established or historic guidelines.

If you adjust the parameters because the rest of the model also has to readjust, it will remake the model and takes much longer for the new image to load.

Does not need to follow any historic guidelines.

If you adjust a certain part of the image, it will change it immediately. There is no waiting.


Though you may start with a sketch idea for both parametric and direct modeling, because of the limitations of parametric modeling, there will be certain things you cannot do with parametric modeling that you can do for direct modeling where you can end up with a 3D image that is completely different in size, shape, and overall appearance.

A simple example is that you may have created the shape of a square, but due to different adjustments, you could end up with an octagon. Whereas if you tried to turn a square into an octagon in a parametric model, not only is it difficult to make the adjustments and time consuming but there is no guarantee that it will successfully render the new image without distorting it or pieces of the model being cut off.

It is much easier to break a parametric model when you make adjustments since each aspect of the model was designed mathematically to work together as a whole unit. The user has to have a strong knowledge of the math that goes into creating the shapes and their relationship to one another. It takes a lot of time, education, and training to become proficient and at ease with parametric modeling.

Direct modeling is much simpler, straightforward, and there is more room for error and testing things out, meaning that users can teach themselves and become proficient at it.

3D Direct Modeling and Its Uses

Because 3D direct modeling has gained popularity due to its simplicity and the ease with which users can learn how to create models, as well as the practicality of being able to adjust aspects of it as necessary to create unique models, it is used in a variety of fields, including the following:

Medical Animation

Due to its decreased memory consumption and faster rendering, direct modeling makes possible the creation of larger, more complex scenes and more optimized workflow, and as we all know time equals money.  There is less worrying about the model falling apart due to its history after many modifications have been made to it when you are working on a tight deadline and there is no room for error.

Medical Manufacturing

Editing faces and other types of direct modeling can be as precise as parametric modeling, yet make the geometry lighter and simpler which means less complications when manufacturing parts.  This is important for items such as boolean operations, where complexity and geometry issues often cause major problems in computation of the final model.  The goal is often to create models that are unique to an individual patient’s anatomy and are not expensive to manufacture.  Direct modeling helps cut down on costs and wasted material.

Here is a video to illustrate 3D direct modeling:



Direct modeling is different from parametric modeling in that the model can be interacted with and changed in real-time. There is no need to change the model’s history as required with parametric modeling, meaning that the user can change and adjust as they see fit without worrying about whether it will mess up the rest of the design.

3D direct modeling has become an increasingly popular and widespread way of creating 3D models and is used in a wide variety of fields from the more technical medical manufacturing field to assist in meeting the specific needs of each patient to artistic fields such as interior design, jewelry, and fashion where change often needs to quickly take place.


Click the following link to find out if 3D modeling is difficult to learn.

Doc J

Dr. J has worked in biology all his life and holds several advanced degrees and certificates in biology, anatomy, scientific illustration, 3d animation and motion graphics. He has always had an interest in teaching others the wonders of biology using the latest advances in graphics, including visualization, digital microscopy, animation, illustration, VR and interactive media.

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