The ObjectARX classes with an AcGe prefix are used by the AcDb library to perform common 2D and 3D geometric operations. AcGe includes utility classes such as vectors and matrices and basic geometric objects such as points, curves, and surfaces.
The AcGe classes can be grouped into two major subsets: classes for 2D geometry and classes for 3D geometry. The major abstract base classes are AcGeEntity2d and AcGeEntity3d. Several basic classes not derived from any other class include AcGePoint2d, AcGeVector2d, and AcGeMatrix2d. These basic classes can be used to perform many types of common operations, such as adding a vector to a point, computing the dot or cross product of two vectors, and computing the product of two matrices. The higher-level classes in this group are implemented using these basic classes.
The AcGe classes provide several different coordinate systems. For more information, see Using the Geometry Library. The sample programs in this documentation illustrate numerous common uses of AcGe classes.