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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For example, the outcode represents a point that is top-right of the viewport. If the region is to the top of the window, the second bit of the code is set to 1. The first bit is set to 1 if the point is above the viewport. Line can be partially inside the window We will find intersection point and draw only that portion of line that is inside region.

In this method if the string is entirely inside the clipping window, then we keep it. In all or none string clipping method, either we keep the entire string or we reject entire string based on the clipping window. It does so by using a 4 bit compuuter called as region code or outcodes.

A polygon can also be clipped by specifying the clipping window. Various techniques are used to provide text clipping in a computer graphics.

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. Learn how your comment data is processed. By using this site, you agree to the Terms of Use and Privacy Policy. Retrieved from ” https: These codes identify location of the end point of line. Consider the following figure, where the rectangle indicates the window.

This algorithm uses the clipping window as shown in the following figure. In this type of graphics, images are stored bit by bit and hence it is named Bit-map graphics. If the endpoint codes are andthe logical OR is and the line can not be trivally accepted. The Cohen—Sutherland algorithm is a computer-graphics algorithm used for line clipping. If the logical OR is zerothe line can be trivally accepted. 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 to the rightthe third bit is set, and if to the bottomthe fourth bit is set. In line clipping, we will cut the portion of line which is outside of window and keep only the portion that is inside the window.

Now pick any arbitrary point P Ei on edge E i then the dot product N i. A bitmap is a collection of pixels that describes an image. Point clipping tells us whether the given point X, Y is within the given window or not; and decides whether we will use the minimum and maximum coordinates of the window.

Cohen–Sutherland algorithm

Compputer 4 bits represent the Top, Bottom, Right, and Left of the region as shown in the following figure. It is a type of computer graphics that the computer uses to store and display pictures.

The bits in the 2D outcode represent: The logical OR of the endpoint codes determines if the line is completely inside the window. From Wikipedia, the free encyclopedia. On the other hand, if the endpoints had codes of andthe logical AND would beand the line could not be trivally rejected. Leave a Reply Cancel reply Your email address will not be published. This is one of the oldest and most popular line clipping algorithm.

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

This clipping method is based on characters rather than the entire string. Reject line segment if any end point of line appears outside of any boundary. Each of the nine regions associated with the window is assigned a 4-bit code to identify the region.

For other convex polygon clipping windows, use the Cyrus—Beck algorithm. Views Read Edit View history. If both endpoints of a line lie inside the window, the entire line lies inside the window. If both codes have a 1 in the same bit position bitwise AND of the codes is notthe line lies outside the window.


If the character is on the boundary of the clipping window, then we discard that entire character and keep the rest string. You May Also Like: If both codes arebitwise OR of the codes yields line lies completely inside the window: Once the codes for each endpoint of a line are determined, the logical AND operation of the codes determines if the line is completely outside of the window.

You can connect with him on facebook. It employs parametric line representation and simple dot products. The Cohen—Sutherland algorithm can be used only on a rectangular clip window. As you proceed around the window, extending each edge and defining an inside half-space and an outside half-space, nine regions are created – the eight “outside” regions and the one “inside”region.

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. If the region is to the left of the window, the first bit of the code is set to 1.

Cohen Sutherland Line Clipping Algorithm in C and C++

The line segment’s endpoints are tested to see if the line can be trivally accepted or rejected. To speed up the process this algorithm performs initial tests that reduce number of intersections that must be calculated.

To clip a line, we need to consider only its endpoints. To determine whether endpoints are inside or outside a window, the algorithm sets up a half-space code for each endpoint.