Cohen-Sutherland Line Clipping Algorithm: When drawing a 2D line on screen, it might happen that one or both of the endpoints are outside. The primary use of clipping in computer graphics is to remove objects, lines, or line This algorithm is more efficient than Cohen-Sutherland algorithm. Department of Computing Science, Umeå University. Computer Graphics & Visualization. Overview. Clipping. ▫ Cohen-Sutherland line clipping algorithm.

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Cohen–Sutherland algorithm

For example, if the endpoint codes are andthe logical OR is – the line can be trivally accepted. The code’s bits are set according to the following conditions:. Your email address will not be published. To determine whether endpoints are inside or outside a window, the algorithm sets up a half-space code for each endpoint.

This clipping method is based on characters rather than the entire string. A polygon can also be clipped by specifying the clipping window.

Each bit position indicates a direction, starting from the rightmost position of each bit indicates left, right, bottom, top respectively. Read 2 corner points of the clipping window left-top and right-bottom as wx1,wy1 and wx2,wy2. To clip a line, we need to consider only its endpoints. By observing the original smiley face closely, we can see that there are two blue lines which are represented as B1, B2 and E1, E2 in the above figure.


In all or none string clipping method, either we keep the entire string or we reject entire string based on the clipping window.

Cohen-Sutherland Line-Clipping Algorithm

In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window. If the endpoint codes are andthe logical OR is and the line can not be algorith accepted. The first bit is set to 1 if the point is above the viewport.

Leave a Reply Cancel reply Your email address will not be published. For better understanding let us consider the following example where we draw a smiley face using bit-map graphics.

If the logical OR is zerothe line can be trivally accepted. This site uses Akismet to reduce spam.

The Cohen—Sutherland algorithm is a computer-graphics algorithm used for line clipping. As you proceed around the window, extending each edge and defining an inside half-space and an clippimg half-space, nine regions are created – the eight “outside” regions and the one “inside”region.

The algorithm divides a two-dimensional space into 9 regions and then efficiently determines the lines and portions of lines that are visible in the central region of interest the viewport. The concept of line clipping is same as point clipping. In line clipping, we will cut the portion of line which is outside of window and keep only the portion that sutherlandd inside the window.


The outcode will have 4 bits for two-dimensional clipping, or 6 bits in the three-dimensional case. You can connect with him on facebook. On the other hand, if both endpoints of a line lie entirely to one side of the window, the line must lie entirely outside of the window.

For example, if an endpoint coheh a code of while the other endpoint had a code ofthe logical AND would be which indicates the line segment lies outside of the window.

It does so by using a 4 bit code called as region code or outcodes. It is trivially accepted and needs no clipping. A bitmap is a collection of pixels that describes an image. The algorithm was developed in during flight-simulator work sutherlqnd Danny Cohen and Ivan Sutherland. Note that the outcodes for endpoints must be recalculated on each iteration after the clipping occurs.

Cohen Sutherland Line Clipping Algorithm in C and C++ – The Crazy Programmer

Cli;ping end point of the line segment is then assigned the code of the region in which it lies. It can be trivially rejected. You May Also Like: