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and complete to all engineering functions from documentation (drafting and shading) to

engineering analysis to manufacturing. Three types of geometric models exist and they are:
wireframes, surfaces, and solids. Users usually have to decide on the type of modeling technique

based on the ease of using the technique during the construction phase and on the expected
utilisation of the resulting database later in the design and manufacturing processes. Regardless of

the chosen technique, the user constructs a geometric model of an object on a CAD/CAM system
by inputting the object data as required by the modeling technique via the user interface provided

by the software. The software then converts such data into a mathematical representation which it

stores in the model database for later use. The user may retrieve and/or modify the model during
the design and/or manufacturing processes.

From an engineering and design point of view, studying geometric modeling provides engineers

and designers with new sets of tools and capabilities that they can use in their daily engineering
assignments. This is an important issue because, historically, engineers cannot think in terms of

tools they have not learned to use or been exposed to. The tools are powerful if utilised
innovatively in engineering applications. It is usually left to the individual’s imagination to apply

these tools appropriately to applications in new context.

4.8 WIREFRAME MODELS

Many CAD/drafting systems use the 3-D wireframe method to define object geometry. In this
method, the user enters 3-D vertices as (x, y, z) triples. Joining the vertices creates a 3-D object

called a wireframe. This representation contains only points and lines (usually straight lines). The
user can inquire about the coordinates of the vertices and the length, in three dimensions, of the

edge. Wireframes still are not complete, however. Surface geometries are not present which may

be important for later manufacturing processing and other analyses. The model contains only the
points and edges.

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