Modified for using OBJ or STL files only?

Hi, is it possible to modify the code to use the OBJ file only? The MTL file is only needed for the material info, so I wonder if it is possible to use a default material. It might be helpful because I think in Solidworks and Fusion 360 (Blender supports I think), exporting MTL files is not supported. Also, would it be hard to modify the code to support the STL format? Thank you.