The file extension OBJ marks 3D model data in Wavefront format. It is a 3D data format developed by Wavefront Technologies (now part of Autodesk) for its Advanced Visualizer in the 1980s. The OBJ format is an open format and is often used today as an exchange format because it can read and write many 3D programs. Some programs like AutoDesk AutoCAD, Dassault Systèmes SolidWorks, Google SketchUp or TrueSpace (luuv plugin) require a plugin to process OBJ files.
OBJ is an ASCII based format and can include 3D model data as well as material references defined in an associated mtl file. Unfortunately, the export functions of some 3D applications are limited in that they can not export all their own geometric descriptions to OBJ and often can not read all data types (eg The Materials).
Most often resolving problems with opening OBJ files is very simple. Just install an appropriate program that supports such files. All of the listed programs support OBJ files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of OBJ files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate OBJ files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the LightWave 3D applications is not on the list, select "Browse" option in order to manually locate the directory where LightWave 3D has been installed.
Sometimes problems with opening OBJ files may not lie with the application itself, but can arise due to other causes, such as: