Geometric Entities

From DocR21

All model geometry classes are derived from the ENTITY class. Thus, these classes inherit all the model management functionality of the ENTITY class. For example, they can be saved to and restored from a file, they can be copied, they can be debugged, and they participate in "undo" and "redo" operations. Model geometry classes can be grouped in four categories:

• zero-dimensional objects that exist in object space - points.
• one-dimensional objects that exist in object space - curves.
• two-dimensional objects that exist in object space - surfaces.
• one-dimensional objects that exist in the parameter space of a surface - pcurves.

Curves can be further categorized as analytic or interpolated curves. Surfaces can be categorized as analytic or sculpted surfaces. All pcurves are interpolated curves. The figure below depicts how points, curves, surface, and parameter space curves are derived from the ENTITY class.

The model geometry classes CURVE and SURFACE are abstract classes and define functionality and data common to their children: CONE, ELLIPSE, HELIX, INTCURVE, PLANE, SPHERE, SPLINE, STRAIGHT, and TORUS. The model geometry classes APOINT and PCURVE are not abstract classes and do not have any children. Additional information for a given class is available in the ACIS Library Reference.