5. Curve and surface models

5.1 Basic models

The two most common types of models in CAD systems are :

• Bézier curves and surfaces ;

• B-spline curves and surfaces.

They can be declined in non-rational or rational form.

These models have properties that can be deduced from the mathematical model used. For example, you won't choose a B-spline or Bézier approach at random, depending on the type of application (although many parameters can be used to vary the influence of the control in both cases).