All About OBJ File Format for 3D Printing

OBJ files offer designers, modelers, 3D printers, and 3D environment builders some powerful options that make it a popular and relied upon format. OBJ supports freeform curves, as a method for defining surfaces. This allows mathematically precise definitions of curvature to make higher quality surfaces than simple tessellation. Cardinal Splines and Bezier Curves reduce file sizes, define whole surfaces in mathematical terms, and reduce the overall quantity of data. Another key feature is that OBJ supports NURBS (Non-Uniform Rational B-Splines). This allows polygons to be defined from a surface that has been manually pulled and shaped by the designer. NURBS surfaces are processed automatically into mathematically precise data. Lastly, the OBJ format in 3D printing is attractive and offers a lower fault/gap count than STL. It has also become indispensable for color prints.

What Are the Types of OBJ Files?

The commonly used OBJ files are in ASCII format. The file contains command lines and # marked annotation lines and associated .MTL files that travel with the .OBJ file. These files can contain extensive materials, textures, and color data as well as complex mathematical descriptions of curved surfaces. But the contents follow a set of agreed format rules that are open source and almost entirely standardized.

OBJ files can also exist in binary format, often with the file type .MOD. The binary conversion of OBJ files is, while open source, not universally agreed upon. So OBJ binary files are often proprietary to applications and require some deep knowledge of format and operation to be used.

What Are the Best OBJ File Converters?

File converters that can handle OBJ are plentiful and usually free. Below are some of the best OBJ file converters:

1. AnyConv.com: AnyConv.com is a simple-to-use, quick, and powerful tool that can convert OBJ files into a limited range of the most commonly used formats—STL, DAE, FBX, GLTF, PLY, and more.
2. Blender: Blender is a powerful design platform for modeling, sculpting, and video design. It also integrates a wide range of file conversion tools and works well with OBJ files.
3. Autodesk Fusion 360: Autodesk Fusion 360 is a powerful CAD/CAM and simulation tool that, while more complex to navigate, offers excellent OBJ handling and conversion capabilities. It is a professional tool that offers a free, limited-function version for home use.

What Are the Best Applications for OBJ Files?

Selecting which tool to use when the data is saved as an OBJ file depends on the nature of the 3D and the tasks to perform. Some of the best applications are:

1. A character design tool such as Blender or ZBrush.
2. A product design package like FreeCAD.
3. A repair/analysis tool like MeshMixer.
4. A slicer like Cura, to make ready OBJ files for 3D printing. 

Is an OBJ File the Same as a CAD File?

Yes, an OBJ file is the same as a CAD file. CAD systems define OBJ files as a universal interchange format. This is because OBJ files contain all the information that a typical CAD system requires to build precise and usable models in its workspace. On that basis, OBJ is a CAD format, although its use is generally more focused on the “character and environment” part of the design spectrum in gaming, architecture, and video creation.

What Is the Difference Between an OBJ and an STL File?

Table 1 shows the differences between OBJ and STL formats:

For more information, see our guide on OBJ vs. STL.