Open Inventor import (.iv) import
Open Inventor is a C++ object-oriented retained mode 3-D graphics toolkit designed by Silicon Graphics to provide a higher layer of programming for OpenGL. Its main goals are better programmer convenience and efficiency.
                                            
Import
                                        To open, import, insert, and attach a file as a worksession
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From the File menu, click Open, Insert, Import, or Worksession > Attach.
 - In the dialog box, select a supported file type.
 - Click  and configure the settings.
When you open a non-3dm file and save the model, its filename will be the default 3dm filename.