Model/CAD Terms

The following model terms are used throughout this Help. They refer to geometric elements in a model, such as faces, edges, and vertices as well as construction geometry, such as reference planes, axes, and the UCS (User Coordinate System).

A Plane (or reference plane) is used as a reference and basis for other actions. The initial reference plane is the XY plane. A reference plane may either be one of the three main (Cartesian) planes (XY, YZ, ZX), or it may be a custom user-defined plane.

A Vertex is a point where two or more curves, lines, or edges meet.

An Edge is a line that joins two vertices. An edge can also be the boundary of a shape. For example, a circle.

A Face is a planar (flat) surface that forms part of the boundary of a solid object.

An Axis is a straight line on which an object may rotate or that divides an object into symmetrical halves.

A UCS (User Coordinate System) is used for orientation to define direction and many other operations.

Other CAD Terms

B-rep	B-rep or BREP (Boundary Representation) is a method for representing shapes using boundary limits. B-rep models are composed of topology (faces, edges, and vertices) and geometry (surfaces, curves, and points). A face is a bounded portion of a surface; an edge is a bounded piece of a curve; and a vertex lies at a point. There are other elements, such as a shell (a set of connected faces) and a loop (a circuit of edges bounding a face).
Mesh	A Mesh model consists of vertices, edges, and faces to create a series of planar regions called facets. These facets are polygons, including triangles and quadrilaterals, used to define a 3D shape. The process of creating a mesh is called tessellation. Once tessellated, the mesh can be subjected to simulated stresses, strains, temperature differences, etc. for FEA (Finite Element Analysis).
Surface	Regular surfaces include surfaces of revolution such as cylinders, cones, spheres, tori, and ruled surfaces (linear in one direction), such as surfaces of extrusion. Freeform surfaces (usually NURBS - Non-Uniform Rational Basis Spline) allow more complex shapes to be represented via freeform surface modeling.
Wireframe	A Wireframe represents a surface as a series of lines and curves. The advantage of this representation is that a great deal of geometry may be displayed and rotated on the screen with no delay needed for graphics processing.
Solid	A Solid is represented as a collection of connected surface elements; the boundary between solid and non-solid.
Point Cloud	A Point Cloud is a set of data points in a coordinate system. In a three-dimensional coordinate system, the points associated with a particular model, image, or graphic are usually defined by X, Y, and Z coordinates. These coordinates (relating to such an image) are called a Point Cloud and represent the external surface of an object. Point clouds are generally produced by 3D scanners, which measure a large number of points on the external surfaces of objects around them. As the output of 3D scanning processes, point clouds are used for many purposes, including to create 3D CAD models.
Facet	A Facet is typically a flat three or four-sided polygon that represents an element of a 3D polygonal mesh surface or model. Multiple facets create a series of planer regions on the mesh surface or model. In Cimatron, facets are usually triangular.

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