Limitations of Wire-frame Modelling:

Although wire-frame modelling is simple and straightforward in concept, it contains a number of limitations as given below.

• In the wire-frame representation, the virtual edges (profile or silhouette) are not generally provided. For instance, a cylinder is represented by three edges, that is, two circles and one straight line. But the straight line is not sufficient to represent the profile or silhouette of a cylinder
• From the point of view of engineering applications, this is not possible to determine volume and mass properties of a design. Other applications, such like NC path generation, cross-sectioning, & interference detection also encounter problems while wire-frame modelling is utilized. Because the wire-frame model database contains only low-level information such like points and lines, the wire-frame methods are restricted in scope when high-level information is needed by particular applications such as process planning.
• There are several wire-frame representation schemes. Though, ambiguous representations of real objects can be created. For instance, the wire-frame model, shown in Figure (a), can be recognized as either a block or an inward corner. Figure (b) can be considered as either a boss or a hole. Figure (c) is just a nonsense object.
• The creation of wire-frame models generally involves more user effort to input essential information than that of solid models, especially for large & complex parts. For instance, consider the creation of a 3-D model of a simple cube. In the wire-frame model, we have to draw 12 lines, whereas with solid modelling methods a cube can be created by providing the positions of three corner points. In addition, the latter model provides more information, such like the inside or outside of the part.

(a)                                      (b)                               (c)

Figure