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 endpoints of a line lie inside the window, the entire line lies inside the window. The algorithm was developed in during flight-simulator work by Danny Cohen and Ivan Sutherland. For any endpoint xy of a line, the code can be determined that identifies which region the endpoint lies. To determine whether endpoints are inside or outside a window, the algorithm sets up a half-space code for each endpoint. You May Also Like: The outcode will have 4 bits for two-dimensional clipping, or 6 bits in the three-dimensional case.
Learn how your comment data sutherlanf processed. For example, the outcode represents a point that is top-right algorithk the viewport. The first bit is set to 1 if the point is above the viewport.
This clipping method is based on characters rather than entire string. If the region is to the top of the window, the second sutherlanv of the code is set to 1. A polygon can also be clipped by specifying the clipping window.
Cohen Sutherland Line Clipping Algorithm in C and C++
For better understanding let us consider the following example where we draw a sutherlahd face using bit-map graphics. An outcode is computed for each of the two points in the line. Each of the nine regions associated with the window is assigned a 4-bit code to identify the region. Grapics 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.
If both codes have a 1 in the same bit position bitwise AND of the codes is notthe line lies outside the window. This is one of the oldest and most popular line clipping algorithm.
On the other hand, if the endpoints had codes of andthe logical AND would beand the line could not be trivally rejected.
PT setcode PT p. It is a type of computer graphics that the computer uses to store and display pictures. The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane. Retrieved from ” https: 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.
To clip a line, we need to consider only its endpoints. 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.
If to the rightthe third bit is set, and if to the bottomthe fourth bit is set. Reject line segment if any end point of line appears outside of any boundary. It employs parametric line representation and simple dot products. To speed up the process this algorithm performs initial tests that reduce number of intersections that must be calculated. The logical OR of the endpoint codes determines if the line is completely inside the window. 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.
Cohen-Sutherland Line-Clipping Algorithm
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. 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.
Let N i be the outward normal edge E i. This process is continued until the line is accepted. 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 is trivially accepted and needs no clipping.
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. In this type of graphics, images are stored bit by bit and hence it is named Bit-map graphics.
From Wikipedia, the free encyclopedia. The concept of line clipping is same as point clipping.
These ib bits represent the Top, Bottom, Right, and Left of the region as shown in the following figure. This page was last edited on 7 Januaryat If the logical OR is zerothe line can be trivally accepted. If it is partially outside the window, then. Each bit in the code is set to either a 1 true or a 0 false.
Cohen Sutherland Line Clipping Algorithm in C and C++ – The Crazy Programmer
It depends on the methods used to generate characters and the requirements of a particular application. This clipping method is based on characters rather than the entire string. If the logical AND of the endpoint codes is not zerothe line can be trivally rejected. Cohen-Sutherland Line Clipping The Cohen-Sutherland line clipping algorithm quickly detects and dispenses with two common and trivial cases. The numbers in the figure below are called outcodes.
It can be trivially rejected. First the polygon is clipped against the left edge of the polygon window to get new vertices of the polygon.