Module 1: Clipping and Hidden Surface Removal

The key points from this module are:

The process of clipping is performed before the objects are projected on to the view plane.

The process of clipping is done through some programs or algorithms, which collectively are known as the Clipping Algorithms.

The Cohen Sutherland algorithm is designed to reduce intersection calculations.

The Sutherland-Hodgeman algorithm works well when the fill area is a convex polygon that is to be clipped against a rectangular clipping window.

Weiler-Atherton algorithm can be used for any polygon, either concave or convex against any polygonal clipping window.

There are two types of 2D clipping:
Point Clipping
Line Clipping

The two main differences between clipping in 2D and clipping in 3D are:
Take one surface at a time to perform clipping.
6 bounding surfaces of the normalized view volume.

In the Objects Space Method, objects and parts of objects are compared to each other to determine visible surfaces.

In the Image Space Method, visibility is decided point-by-point at each pixel position on the projection plane.

The Depth Sorting algorithm is also known as the painter’s algorithm, and it works at both image and object space.

In the Depth Sorting Algorithm, in case if all the tests fail, the order of the surfaces in the list is swapped and this process is called Reordering.