Default-meshes.igs is an igs file that contains the mesh information of a scene. It is referenced from a main igs file and cannot be rendered by itself, you must open the main file (either default.igs or a set file-name) to render.
This file is created separately and referenced so that a exporter can export either [i]just[/i] mesh data, or [i]all other[/i] data without having to rebuild the meshes (which is usually the longest part of an export). This feature is known as "Quick Export".
