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What is the difference between NURBs model and a mesh?

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What is the difference between a NURBS-Model and a Polygon Mesh? 03:11
A NURBS model consists of points connected by curves. A polygon mesh consists of thousands or millions of small triangles. CAD surface models are usually created using NURBS surfaces, while 3D scans are typically exported as a polygon mesh. The conversion from a polygon mesh to a NURBS model is called “reverse engineering”.
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Comparable with Pixel and Vector Graphics

The easiest way to describe the difference between polygon meshes and NURBS models is to
compare them to 2D computer graphics:


Graphics on the computer exist either as pixel graphics or as vector graphics. In a pixel graphic, the
image consists of many pixels. Each pixel has a specific color. If you enlarge the graphic on the
computer and then print it on a large sheet of paper, the image becomes blurred. This is because the
individual square pixels have been enlarged, but not the total number of pixels.


There are no pixels in a vector graphic; there are only a few points connected by curves. These
curves are recalculated each time the graphic is resized. A vector graphic can thus be enlarged as
desired, and a printout will always be razor-sharp.

Meshes Are Like Pixel Graphics and NURBS models Are Like Vector Graphics

In a polygon mesh, the surface is represented by many triangles. If a small polygon mesh is enlarged
and printed in 3D, all previously round surfaces of the object will come out of the 3D printer angular.
The polygon mesh does not have enough triangles to create a cleanly curved surface.

3D scan of a sports car model
Swann Rack / Holocreators Polygon mesh of a stylized sports car. You can download the polygon mesh here.

With NURBS models, enlarging the image is not a problem. Curves define the object’s surface. The
curves maintain the object’s perfect shape, no matter how much the 3D model is magnified. The
curves are defined by a few control points, and an algorithm recalculates the curves each time the
3D model is resized.

NURBs surface model of a sports car model
Swann Rack / Holocreators NURBS model of the same stylized sports car. You can download the NURBs model here

Download the example files of a Polygon Mesh and a NURBs model

You can take a look at the difference between a Polygon Mesh and a NURBs model. We have
prepared both for you to download. You will need a 3D viewer like Meshlab to look at the STL-file
and a CAD Software like FreeCAD to look at the STEP-file.

Conclusion

NURBS 3D models are infinitely scalable without loss of surface quality. Whenever possible, NURBS
models are preferred over polygon meshes. However, NURBS models are much more complicated to
create and more difficult to edit. Therefore, polygon meshes are used more often.

Do you have any further questions about polygon meshes and NURBS models?

Holocreators offers professional 3D-scanning and reverse engineering services. We are happy to
advise you on the topic of polygon meshes and NURBS models. Please call us at +49 40 481133 or send an email info@holocreators.com

Swann has been enthusiastic about everything 3D for many years. His roots lie in analog holography, which brought him to digital 3D-modeling in 2011.

The rapid progress of various 3D-scanning techniques fascinated himso much thathe founded Holocreators together with his brother Miro Rack in 2015.

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