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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If both codes arebitwise OR of the codes yields line lies completely inside the window: Chen polygon can also be clipped by specifying the clipping window. Let N i be the outward normal edge E i. The code’s bits are set according to the following conditions:. For other convex polygon clipping windows, use the Cyrus—Beck algorithm.
Viewing & Clipping
You can connect with him on facebook. The line segment’s endpoints are tested to see if the line can be trivally accepted or rejected. For example, the outcode represents a point that is top-right of the viewport. If it is partially outside the window, then. Line can be partially inside the window We will find intersection point and draw only that portion of line that is inside region.
Read 2 corner points of the clipping window left-top and right-bottom as wx1,wy1 and wx2,wy2. If the character is on the boundary of the clipping window, then we discard that entire character and keep the rest string.
To speed up the process this algorithm performs initial tests that reduce number of intersections that must be calculated. It can be trivially rejected. If the endpoint codes are andthe logical OR is and the line can not be trivally accepted. Note gra;hics 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
It is trivially accepted and needs no clipping. Learn how your comment data is processed. The first bit is set to 1 if the point is above the viewport.
If the logical OR is zerothe line can be trivally accepted. It is trivially rejected and needs to be neither clipped nor displayed.
It employs parametric line representation and simple dot products.
Viewing and Clipping
To clip a line, we need to consider only its endpoints. These 4 bits represent the Top, Bottom, Right, and Left of the region as shown in the sutherlnd figure. You May Also Like: If the logical AND of the endpoint codes is not zerothe line can be trivally rejected. Clipping a point from a given window is very easy.
If to the rightthe third bit is set, and if to the bottomthe fourth bit is set. 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. For any endpoint xy of a line, the code autherland be determined that identifies which region the endpoint lies.
Now pick any arbitrary point P Ei on edge E i then the dot product N i. It does so by using a 4 bit code called as region code or outcodes. A bitmap is a collection of pixels that describes an grsphics. Cohen-Sutherland Line Clipping The Cohen-Sutherland line clipping algorithm quickly detects and dispenses with two common and trivial cases.
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Line can be completely outside of the window This line will be completely removed from the region. Retrieved from ” https: 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.
The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane. The algorithm was developed in during flight-simulator work by Danny Cohen and Ivan Sutherland. Leave a Reply Cancel reply Your email address will not be published.
This algorithm is more efficient than Cohen-Sutherland algorithm. In all or none string clipping method, either we keep the entire string or we reject entire string based on the clipping window. 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.
The logical OR of the endpoint codes determines if the line is completely inside the window. 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.
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. The 4 bits in the code then identify each of the nine regions as shown below.