File formats
IGES
Initial Graphics Exchange Specification
Definition
IGES is an older neutral format for exchanging CAD geometry, developed in the United States. It still appears in legacy workflows and for surface data, but STEP has largely replaced it for solid models.
Also known as: IGS, .igs, .iges, Initial Graphics Exchange Specification
Updated
IGES and STEP#
The STEP Tools history lists IGES alongside SET in France and VDAFS in Germany as the national exchange formats that the ISO STEP effort was created to unify.
IGES files often arrive as collections of surfaces rather than closed solids, so the receiving CAD program may have to stitch them before the part can be used. When a supplier offers both, STEP is usually the better choice for mechanical parts.
Sources
Related terms
STEP
STEP is the ISO 10303 family of standards for exchanging 3D product data between CAD systems, usually saved as .step or .stp files. A STEP file carries exact B-Rep solid geometry that another CAD program can measure and edit, but it normally does not carry the original feature history.
B-Rep
B-Rep is the way professional CAD kernels describe a solid: by its boundary, made of exact surfaces (faces), the curves where they meet (edges), and the points where edges end (vertices). Because the geometry is exact and the topology is explicit, B-Rep models can be measured, filleted, dimensioned, and manufactured precisely.
NURBS
NURBS are mathematical curves and surfaces that can represent both simple shapes, such as lines, arcs, and circles, and complex freeform surfaces exactly. CAD kernels use them for the faces and edges of B-Rep solids that are not simple planes or cylinders.