Surface Modeling is the method of showing or presenting solid objects. The process requires you to convert between different 3D modeling types, such as converting the 3D object to show procedural surfaces, validate imperfections, and apply smoothness. While more complex than Wireframe Modeling, Surface Modeling is easier to achieve than Solid Modeling.
In a CAD environment it is possible to fully produce a model using only surface modeling - but most real-world applications require a combination with solid modeling technique as well. How a designer is able to interact and manipulate an object in a CAD system is the difference between solid and surface modeling.
Surface Modeling Explained
Surface modeling gives you the ability to build out a visual representation of an object’s exterior and its contours. In other words, it’s a surface.
These objects can be mechanical components like an engine - or complex organic shapes like animals.
No matter what you’re designing, surface modeling requires you to define the exterior curves and shapes of your objects.
Unlike solid modeling, your object can be geometrically and physically incorrect - with no properties of mass defined and no thickness. This gives the designer the unique ability to modify the model in ways that solid models are incapable.
This also means, however, that surface models cannot be sliced open like their solid counterparts, because the object is essentially hollow.
Also, note that these surfaces can be represented using NURBS or polygons, depending on the application. Solidworks typically uses NURBS in its surface modeling operators.
So, What Can You Do With Surface Modeling?
Surface modeling uses B-splines and Beizer equations in order to define the features of your solid appearing object - and is used in architectural illustrations and 3d animation for video games. This gives the following distinct advantages over other techniques:
Make Changes to an Imported Model
When you import existing models into a CAD environment that it wasn’t originally built, it can present a host of issues - most notably it opens without any details of the features it’s made up of.
Making changes to complex surfaces without these details can be extremely challenging. The flexibility of surface modeling allows you to delete or replace faces of the model in order to make your desired changes.
Design More Complex Shapes
Solid modeling tools have their limitations - like having to build out several sides of a shape at once. Surface modeling lets you build out faces individually, giving you control over the exact contour and direction.
Create a Fillet or Draft Between Faces
Sometimes in solid modeling you will get an error message when trying to create a draft or fillet between 2 or more faces of an object - “Invalid, unable to create feature.” However attempts to use different settings or tools result in error.
This can occur when the resulting change would create a self-intersecting face - but in surface modeling you can delete the face, reconstruct it, and stitch it back to the existing design.
Which Modeling Technique is Better?
Surface and solid modeling both have their pros and cons - being a great designer is about understanding how to leverage this in order to efficiently and accurately design models in a CAD environment.
Where you can slice and extrude in a solid model, surface modeling is better for shaping mesh objects - giving designers the ability to create levels of smoothness and manipulate mesh faces by “dragging” the edges, in order to perfect the design.