Brep or boundary representation is a way of defining geometric forms using edges, faces and vertices. The advantage is that these edges are stitched together, so with the addition of surface data, this too can be stitched into a complex solid model.
Entities such as cone, plane, torus, cylinder and sphere can be easily represented by Brep technology as their intersections and edges can be exactly calculated. The result is a solid model defined by its edges. With Nurb surfaces, the edges are not so exact, as different CAD systems will have small calculation inconsistencies which can result in microscopic gaps between surfaces. Additionally, surfaces have direction, so this may be pointing in the wrong direction. With Brep, these edge gaps can be stitched together and surface direction modified to form a solid entity.
For STL data, the representation is mainly through triangles and quadrilaterals which approximate to the surface. Smoothing techniques in Brep, which work on the boundaries of these elements, can help to improve the surface topology by reducing the number of triangles required to define a component.
The majority of CAD systems use Brep technology so translation between different systems using the same technology is considerably easier. Other advantages include the ability to carry out sophisticated analysis of the geometry to determine volumes or surface areas, for example. Sescoi’s WorkXPlore 3D mark-up and analysis software uses Brep technology, enabling it to import CAD models from a wide range of systems and, because it can find edges very easily, it can give accurate dimensions and volumes. For imported STL files, it can also smooth and simplify the result to give a better representation of the scanned part making it much easier to interrogate and use. Good stuff this Brep technology….