VISUAL REALISM:

Hidden line and surface removal eliminates the ambiguities of the displays of three-dimensional models and is considered the first step toward visual realism.

A large number of techniques have been developed for eliminating hidden surfaces and lines which is a fundamental problem in computer graphics. Hidden surface removal (HSR) algorithms are complex and take long execution times. A great effort is paid to improve their efficiency. Though wire-frame views of the objects can be drawn very quickly, it is hard to interpret them when a several objects in scene overlap. Visual realism is greatly enhanced while the faces of the objects are filled with some colours and the surfaces that must be hidden are removed.

This unit discusses regarding various algorithms for hidden line or hidden surface removal. The pictures that are rendered by filling the faces of the object with colours and removing the hidden surfaces still do not give the impression of objects residing in a scene, illuminated by light source. A shading model describes how light reflects off a surface, depending on the nature of the surface and its orientation to both light source and the camera's eye. Shading procedure as Gouraud & Phong shading is discussed.