
Geometric models of virtual environments 323
makers use models based on skew surfaces, which are later triangulated in order to
simplify the rendering calculations. Triangulation, a complicated problem addressed
in section 14.4, is necessarily a compromise between the precision of the triangulated
model, the time required for rendering and the time taken for the triangulation.
These days, the model makers favour NURBS surfaces for modelling objects.
For example, CATIA for CAD and also 3DS Max for computer graphics. With
file formats dedicated to virtual reality (for example, VRML), it is also possible to
directly incorporate NURBS surfaces, even though ...