MODELING

Modelling typically includes a set of activities like

<!--[if !supportLists]-->¨         <!--[endif]-->Defining objects

<!--[if !supportLists]-->¨         <!--[endif]-->Defining relation between objects

<!--[if !supportLists]-->¨         <!--[endif]-->Defining properties of objects

<!--[if !supportLists]-->¨         <!--[endif]-->Defining the orientations of the objects in suitable co-ordinate systems

<!--[if !supportLists]-->¨         <!--[endif]-->Modification of existing definition (editing).

The figure below explains what a typical CAD model would need to define, what kind of entities need to be defined and what relationships exist between them.

At the highest level we have the volume which is by (or "delimited by") a set of surfaces. These surfaces can be either planar or curved / warped. A planar surface can be bounded by a set of curves. A curved surface can be seen as a net of curves. These curves are typically a succession of curve segments which define the complete the curve. The curve segment is defined using a set of end points / control points which govern the nature of the curve.  Thus a relationship is defined between entities at each level.

Once such a relationship is defined, a geometric model of the artifact is available. In any design there might be many such artifacts. One then has to define properties of each of these artifacts and define a relationship between   them.   The   properties   and   the   relationships   needed   are dependent on the application the model is to be used for subsequently. But one common application that all model have to go  through  is visualization of the model (s).