IGES

IGES
US Government (NIST), traced by User:Stannered · Public domain · source
Name	Initial Graphics Exchange Specification
Extension	.igs, .iges
Mime	application/iges, model/iges
Owner	United States Air Force, American National Standards Institute, International Organization for Standardization
Released	January 1980
Type code	IGES
Uniform type	public.iges
Genre	Computer-aided design, Computer-aided manufacturing, Data exchange

IGES. The Initial Graphics Exchange Specification is a vendor-neutral file format used for the digital exchange of CAD and CAM data between different software systems. Developed in the late 1970s with support from the United States Air Force, it became one of the first widely adopted standards for 3D model interoperability, facilitating collaboration in industries like aerospace and automotive manufacturing. Although largely superseded by newer formats like STEP, IGES remains a foundational protocol in the history of computer-aided engineering.

Overview

The primary purpose of IGES is to enable the translation of geometric models and associated product data between disparate CAD software platforms, which often use proprietary data structures. It functions as a neutral intermediary, describing a model's boundary representation (B-rep) using entities like NURBS surfaces, Bézier curves, and wireframe constructs. This capability was crucial for major defense contractors like Boeing and General Dynamics, as well as automotive giants like General Motors, allowing them to share complex engineering drawings and assembly data with subcontractors. The format is formally standardized by both the American National Standards Institute (as ANSI Y14.26M) and the International Organization for Standardization (as ISO 10303-21).

History and development

The development of IGES was initiated around 1979 by a consortium including the United States Air Force's Integrated Computer-Aided Manufacturing (ICAM) program, the National Bureau of Standards (now NIST), and industry leaders like General Electric and McDonnell Douglas. A key driver was the US Department of Defense's need to integrate CAD/CAM systems from different vendors, such as IBM, Computervision, and Applicon, used on projects like the B-1 Lancer bomber. The first official version, IGES 1.0, was published in January 1980, with subsequent revisions (like Version 5.3 in 1996) adding support for solid modeling via CSG and more advanced geometric dimensioning and tolerancing. The effort was closely tied to other contemporary initiatives like the Product Data Exchange Specification (PDES).

Technical specification

An IGES file is an ASCII text file (with an optional binary variant) organized into five distinct sections: Start, Global, Directory Entry, Parameter Data, and Terminate. The format represents objects through a collection of entities, each defined by a type number; for example, Type 100 is a circular arc, Type 126 is a rational B-spline curve, and Type 144 is a shell for boundary representation. It supports wireframe, surface, and solid representations, though its implementation of Boolean operations on solids was often inconsistent. The geometric tolerancing and layer information are also encoded, but the format does not preserve parametric history or assembly constraints, leading to potential data loss during translation.

Applications and usage

Throughout the 1980s and 1990s, IGES became the *de facto* standard for exchanging mechanical and electrical drawings across industries. It was extensively used in aerospace projects involving Lockheed Martin and Northrop Grumman, in automotive design at Ford Motor Company and Toyota, and in shipbuilding at companies like Newport News Shipbuilding. The format was particularly valuable for sending toolpath data to CNC machines for machining and for transferring finite element meshes to simulation software like ANSYS. Despite its limitations, its widespread support in major CAD software packages such as Autodesk AutoCAD, CATIA, Siemens NX, and PTC Creo ensured its longevity in legacy workflows.

Related standards and formats

The limitations of IGES, particularly in representing complete product lifecycle data, led to the development of its more robust successor, STEP (ISO 10303), which supports feature-based modeling and material properties. Other contemporary or competing formats include DXF from Autodesk, primarily for 2D vector graphics, and STL, which is dominant in 3D printing and rapid prototyping. The VRML format also emerged for web-based 3D visualization, while specialized standards like EDIF were created for electronic design automation. The ongoing work of the International Organization for Standardization technical committee ISO/TC 184 continues to evolve these data exchange protocols. Category:Computer-aided design Category:File formats Category:American National Standards Institute standards