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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Learn how your comment data is processed. Let N i be the outward normal edge E i. If both computet of a line lie inside the window, the entire line lies inside the window.
The line segment’s endpoints are tested to see if the line can be trivally accepted or rejected. Cohej is a type of computer graphics that the computer uses to store and display pictures. The outcode will have 4 bits for two-dimensional clipping, or 6 bits in the three-dimensional case. The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane.
The Cohen-Sutherland algorithm uses a divide-and-conquer strategy. This algorithm uses the clipping window as shown in the following figure. The 4 bits in the graphkcs then identify each of the nine regions as shown below.
For example, if the endpoint codes are andthe logical OR is – the line can be trivally accepted. Once the codes for each endpoint of a line are determined, the logical AND operation of the codes copmuter if the line is completely outside of the window.
Viewing and Clipping
If both codes have a 1 in the same bit position bitwise AND of the codes is notthe line lies outside the window. The concept of line clipping is same as point clipping. First the polygon is clipped against the left edge of the polygon window to get clippin vertices of the ij. 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.
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.
This algorithm is more efficient than Cohen-Sutherland algorithm. These 4 bits represent the Top, Bottom, Right, and Left of the region as shown in the following figure. If the region is to the top of the window, the second bit of the code is set to 1. For any graphlcs xy of a line, the code can be determined that identifies which region the endpoint lies. You can connect with him on facebook.
This page was last edited on 7 Januaryat 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. Each bit in the code is set to either a 1 true or a 0 false. This site uses Akismet to reduce spam.
Viewing & Clipping
If the logical OR is zerothe line can be trivally accepted. If the region is to the left of the window, the first bit of the code is set to 1. For other convex polygon clipping windows, use the Cyrus—Beck algorithm.
If to the rightthe third bit is set, and if to the bottomthe fourth bit is set. The Cohen—Sutherland algorithm is a computer-graphics algorithm used for line clipping. Each bit position indicates a direction, starting from the rightmost position of each bit indicates left, right, bottom, top respectively. This is one of the oldest and most popular line clipping algorithm. For example, the outcode represents a point that is top-right of the viewport. While processing an edge of a polygon with clipping window, an intersection point is found if edge is not completely inside clipping window and the a partial edge from the intersection point to the outside edge is clipped.
You May Also Like: To speed up the process this algorithm performs initial tests that reduce number of intersections that must be calculated.