This article explains what IGS files are, how to open them, and, depending on the format, how to convert them to STL, STP, DWG, DXF, and other similar files.
HOW TO CONVERT AN "IGES" TO A "SOLIDWORKS PART" FILE
A file with the IGS file extension is most likely an IGES drawing used by CAD programs to store vector graphic data in an ASCII text format.
IGES files are based on the Initial Graphics Exchange Specification (IGES) and were once a widely used standard for transferring 3D models between different CAD applications. However, many programs also rely on the STEP 3D CAD format (.STP files) for the same purpose.
Some files ending in .IGS may instead be Indigo Renderer scene files used by Indigo's Renderer or RT program. These, after being exported from a 3D modeling program such as Blender, Maya, Revit, etc., are then imported into Indigo's software to generate a photorealistic image.