In computer-aided design, the term boundary representation — often abbreviated as B-REP or BREP, refers to storing information about how to make a model based on its geometric and often Euler topological boundaries. ECAD redirects here. ...

Often, a user builds the model in CSG format, but stores it in BREP. In facetted and advanced surface BREP STEP format (part 42), the Euler topological representation is vertex, edge, half-edge, face loop, face, shell, and body and refer to the underlying geometric representations. The geometric representation is the point, line, surface (e.g. plane, sphere, cone, torus), solid, void and etc. Other formats like Mantyla's (Geometric Work Bench) GWB and ACIS's SAT use similar names. Constructive solid geometry (CSG) is a technique used in solid modeling. ... Geometric Work Bench is a BREP file format introducted by Marti Mantyla and discussed in his book An Introduction to Solid Modeling. This file format is used by several open source CAD CAM modelers as well as MELCAD. External Link http://www. ... Acis was, in Greek mythology, a Sicilian youth who was often considered the son of Dionysus. ...

Newer, parametric based CAD systems, store both (CSG & BREP) representations, which allow subsequent modifications and regeneration of the BREP. Due to the work of Braid, Euler boolean operations have gained favor because the operations generate an Euler consistent (satisfies the Euler characteristic) BREP at every stage of the constructions process. An Euler consistent BREP is one which satisfies Euler's equation at every stage. Often, this is implanted by capturing the representation in a change state, so that if a problem is encountered (e.g. programming exception) or the model is not Euler consistent, the model state is reverted back to its original state. Acis was, in Greek mythology, a Sicilian youth who was often considered the son of Dionysus. ... It has been suggested that Vertex/Face/Edge relation in a convex polyhedron be merged into this article or section. ... In CAD or CSG, the change state or delta state (as defined by Spatial Technologies ACIS) refers to the intermediate modifications made to a document before it is saved. ...

STEP ISO 10303 (Standard for the Exchange of Product model data) is an ISO CAD standard introduced in the 1990's replacing and extending IGES. The official title of ISO 10303 is Industrial automation systems and integration - Product data representation and exchange. ... The Initial Graphics Exchange Specification (IGES) (pronounced eye-jess) defines a neutral data format that allows the digital exchange of information among Computer-aided design (CAD) systems. ...

See also Winged edge The winged edge data structure is a commonly used data representation used to describe polygon models in computer graphics. ...

Actual example of source boundary representation in STEP format: http://wheger.tripod.com/step