Mesh vs. NURBS: Which 3D Model Is Best for 3D Printing?

Each modeling system has benefits, but mesh is slightly faster

3D printing machine with CAD design on screen in orthopaedic factory
Monty Rakusen / Getty Images

When designing a 3D object using a CAD program, the most popular modeling programs use either “polygon mesh” or a “Non-Uniform Rational Basis Spline” (NURBS) to describe the object.

On the path to creating a file for 3D printing, most CAD programs allow you to convert the file to STL format (which is converting it to a triangular polygon mesh), so you may be wondering if you should create the object with mesh from the beginning or if it is better to work in NURBS and then make the conversion.

Overall Findings

Mesh
  • Smaller file sizes

  • Easier to modify models

  • Most compatible with the STL format; no need to convert

  • Fully 3D rendering, so no "seams" from patching pieces together

NURBS
  • More accurate, less pixelated models

  • Better for engineering and mechanical applications

  • Can render smooth shapes

Polygon mesh was created specifically to render 3-dimensional items on the computer. Because of this, it is the format used by STL files for 3D printing. When using triangles to create 3D shapes, you create approximations of smooth edges. You will never achieve the perfect smoothness of an image initially created in NURBS, but the mesh is easier to model. You can push and pull on the mesh to move it and achieve the same results each time because it is not calculating mathematical averages of points.

As far as computer modeling goes, NURBS will create the smoothest images. It will also create the most accurate models with even edges that are not pixilated. For engineering and mechanical applications, NURBS-based computer rendering is preferred to polygon mesh-based programs. Generally, when you scan objects into a CAD program, they are initially scanned using NURBS.

Compatible Programs: Both Have Free and Premium Versions

Mesh
  • Free and commercial software

NURBS
  • Free and commercial software

  • Most programs handle both polygon and NURBS

Both polygon mesh and NURBS users have a variety of free, freemium, and commercial software programs to use. And many of them have both options built-in. If you're using the free software Blender to make a movie, for example, you could make your characters with polygons but use NURBS for the environment to get natural-looking terrain with organic curves.

The other major NURBS programs include Autodesk Maya, Rhinoceros, and AutoCAD, but they also include polygon mesh. SketchUp's basic, free version only supports polygons in its native tools. But the Pro edition supports extensions that let you approximate NURBS processes like smooth curves.

Whichever tool you want to use, you don't have to spend hundreds of dollars to start making models, but some of the more powerful software does come at that kind of cost.

Ease of Use: Mesh Gets You Modeling and Printing Faster

Mesh
  • Use lines and shapes in three dimensions to quickly assemble models

  • Harder to make smooth curves

NURBS
  • Assemble models using "patches" of two-dimensional objects

  • Gaps may show up from bad joins

  • Way easier to do smooth surfaces

NURBS is better at rendering curved surfaces, although you can make approximations in a mesh model by increasing the number of sides in your polygons.

NURBS does have its limitations. Because it is a 2-dimensional rendering form, you need to create “patches” that you piece together in order to make a complex 3-dimensional shape. In some cases, these patches do not fit together perfectly and “seams” appear. It is crucial to look carefully at your object when designing it and make sure the seams align perfectly before you convert it to mesh for the STL file.

For beginners, mesh polygons programs are a good starting point to get the basics of 3D modeling down. It doesn't take long to get to a basic model.

3D Printing: Polygon Mesh Is Faster

Mesh
  • Can convert directly to STL

NURBS
  • Must convert to mesh before exporting as an STL file

If you're modeling for the purpose of 3D printing, polygon mesh has a slight advantage over NURBs. You can't convert a NURBS file directly into STL format (the file type that slicing software uses to generate the instructions for the printer). You have an extra step of converting it to a mesh first.

When you work in NURBS and convert the file into a mesh, you can choose your resolution. High resolution gives you the smoothest curves in the object you are printing. However, high resolution means you will have a large file. In some cases, the file may be too large for the 3D printer to handle.

Aside from finding the perfect balance between resolution and file size, you can use other cleaning methods to reduce your file size. For example, you need to make sure that when you crafted the object you did not create inner surfaces that will not be printed. One way this could happen is if you join two shapes together, sometimes the join surfaces remain defined, even though, when they print, they will not be separate surfaces.

Overall Findings

The bottom line: The 3D Design program that you are most comfortable with will most likely have an option to export your NURBS or mesh file to an STL or another 3D-printing format.

Whether you initially make your object using NURBS or mesh will depend on your preference. If you want an easier program that you will not have to convert, starting in the mesh will be the best option. On the other hand, if you want a program that gives you perfect curves, you should choose one that uses NURBS.

Other great resources for understanding different model formats come from 3D printing service bureaus (such as Sculpteo and Shapeways). These firms have to handle file types and formats from nearly every 3D design program on the planet and often have great tips and suggestions for getting your files to print right.