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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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 other convex polygon clipping windows, use the Cyrus—Beck algorithm.
Cohen Sutherland Line Clipping Algorithm in C and C++
It does so by using a 4 bit code called as region code or outcodes. If the region is to the top of the window, the second bit of the code is set to 1. 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. 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.
Cohen–Sutherland algorithm – Wikipedia
If the character is algorjthm the boundary of the clipping window, then we discard only that portion of character that is outside of the clipping window. For example, the outcode represents a point that is top-right of dohen viewport. These 4 bits represent the Top, Bottom, Right, and Left of the region as shown in the following figure. 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.
The Cohen—Sutherland algorithm can be used only on a rectangular clip window. Your email address will not be published. Each of the nine regions associated with the window is assigned compuuter 4-bit code to identify the region. Each edge of the window defines an infinite line that divides the whole space into two half-spaces, the inside half-space and the outside half-spaceas shown below.
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The Cohen—Sutherland algorithm is a computer-graphics algorithm used for line clipping. The code’s bits are set according to the following conditions:. In this type of graphics, images are stored bit by bit and hence it is named Bit-map graphics. On the other hand, if the endpoints had codes of andthe logical AND would beand the line could not be trivally rejected.
These codes identify location of the end point of line. The concept of line clipping is same as point clipping. Learn how your comment data is processed. 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. If to algrithm rightthe third bit is set, and if to the bottomthe fourth bit is set. The algorithm was developed in during flight-simulator work by Danny Cohen and Ivan Sutherland. The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane. This clipping method is based on characters rather than the entire string.
Cohen-Sutherland Line-Clipping Algorithm
The 4 bits in the code then identify each of the nine regions as shown below. The logical OR of the endpoint codes determines if the line is completely inside the window. Clipping a point from a given window is very easy.
For better understanding let us consider the following example where we draw a smiley face using bit-map graphics. Reject line segment if any end point of line appears outside of any boundary. It is trivially rejected and needs to be neither clipped nor displayed. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window.
It depends on the methods used to generate characters and the requirements of a particular application. It employs parametric line representation and cokputer dot products. Sutherland Hodgeman polygon clipping algorithm is used for polygon clipping.
This algorithm is more efficient than Cohen-Sutherland algorithm. In this method if the string is entirely inside the clipping window, then we keep it. If the region is to the left of the window, the first bit of the code is set to 1.
Note that the outcodes for endpoints must be recalculated on each iteration after the clipping occurs.
Point clipping tells us whether the given point X, Y is within the given window or not; and decides whether we algprithm use the minimum and maximum coordinates of the window. If both codes arebitwise OR of the codes yields line lies completely inside the window: The bits in the 2D outcode represent: