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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These 4 bits represent the Algorjthm, Bottom, Right, and Left of the region as shown in the following figure. We will use 4-bits to divide the entire region. It is trivially accepted and needs no clipping. The algorithm was developed in during flight-simulator work by Danny Cohen and Ivan Sutherland.

Viewing & Clipping

The concept garphics line clipping is same as point clipping. If both endpoints of a line lie inside the window, the entire line lies inside the window. The numbers in the figure below are called outcodes. Wlgorithm employs parametric line representation and simple dot products.

Each bit position indicates a direction, starting from the rightmost position of each bit indicates left, right, bottom, top respectively. You May Also Like: 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. It does so by using a 4 bit code called as region code or outcodes. Each end point of the line segment is then assigned the code of the region in which it lies.

PT setcode PT p. 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. Leave a Reply Cancel reply Your email address will not be published.


If the endpoint codes are andthe logical OR is and the line can not be trivally accepted. A polygon can also be clipped by specifying the clipping window. Various techniques are used to provide text clipping in a computer graphics.

The 4 bits in the code then identify each of the nine regions as shown below. Now pick any arbitrary point P Ei on edge E i then the dot product N i. The Cohen-Sutherland algorithm uses a divide-and-conquer strategy.

These new vertices are used to clip the polygon against right edge, top edge, bottom edge, of the clipping window as shown in the following figure. If both codes arebitwise OR of the codes yields line lies completely inside the window: Each of the nine regions associated with the window is assigned a 4-bit code to identify the region.

If the logical AND of the endpoint codes is not zerothe line can be trivally rejected. It depends on the methods used to generate characters and the un of a co,puter application. Line can be completely outside of the window This line will be completely removed from the region.

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

If the character is on the boundary of the clipping window, then we discard that entire character and keep the rest string. Let N i be the outward normal edge E i. This algorithm uses the clipping window as shown in the following figure. For other convex polygon clipping windows, use the Cyrus—Beck algorithm. Learn how your comment data is processed. This site uses Akismet to reduce spam. From Wikipedia, the free encyclopedia. It is trivially rejected and needs to be neither clipped nor displayed.


To determine whether endpoints are inside or outside a window, the algorithm sets up a half-space code for each endpoint. Consider the following figure, where the rectangle indicates the window. Line can be partially inside the window We will find intersection point and draw only that portion of line that is inside region. An outcode is computed for each of the two points in the line.

These codes identify location of the end point of line. First the polygon is clipped against the left edge of the polygon window to get new vertices of the polygon. It can be trivially rejected. Note that the outcodes for endpoints must be recalculated on each iteration after the clipping occurs.

The first bit is set to 1 if the point is above the viewport. To perform the trivial acceptance and rejection tests, we extend the edges of the window to divide the plane of the window into the nine regions. For example, if an endpoint had 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. If it is partially outside the window, then.