Research On Algorithms About A Routine Clipping

In this era of rapid technological development, computer science aroused a lot of people’s interest who want to get involved in from the date of birth. She seems a leafy tree, full of vitality, endless. With the development of computer science and technology, computer graphics has gradually grown into a young and important subject in the field of computer science, and is widely used in all areas of life as one of the most active branches in computer science and technology. Nowadays, the graphics have more and more become one of the main carriers to deliver all kinds of information. In a sense, the application of graphics indicates the computer software and hardware technology development level, meanwhile is the basis for many important issues with a wide range of applications in CAD, CAM.Graphic as the object of study in computer graphics, whose main geometric elements of its composition are the point, line, surface, body and so on which are used to depict shape. In specific applications, each graphic is composed of the hundreds of straight lines and curves, thus the processing speed and quality of each straight line and curve directly affects the whole graphics. Therefore, the research on the basic algorithm for computer graphics is extremely important and meaningful. Clipping algorithm is one of the basic researches in computer graphics. Clipping, that is, the process of identifying a designated area out of the region in the needed information. By definition, is to select from specified graphical data, to do further action for the specified area. The most basic purpose is to determine the designated area which is called the window (rectangular window owns the broader application) within a scene. Clipping is to define the selected areas into this window. In computer graphics processing system, clipping is a regular and essential operation, and its principle is based on displaying a partial content of a large graphic with a window, only the content in line with the boundary conditions of the window can be shown, and not consistent with boundary conditions of the window needs to be removed.Currently, due to the operation of the mouse pointer and display limitations, leading to more commonly used for the rectangular window clipping [1]. Rectangular window clipping on the line [2][3] and there are many classical polygon clipping algorithms, such as the Cohen-Sutherland algorithm [4], the midpoint of the segmentation algorithm [5], Liang-Barsky algorithm [6], Sutherland-Hodgon [1] algorithm and the Nicholl-Lee-Nicholl algorithm [7]. In practice, the circle clipping operation is also very common, such as the mechanical components of the test, two-dimensional animation design, robot kinematics and so on. Since curve belongs to second circle, therefore, the use of algorithm which generated from the original circle approximation can cause the problems of computational complexity and low efficiency. For this reason, some scholars studied the circle clipping, and the corresponding algorithm was proposed, such as:[8] proposed a circle curve on rectangular window clipping algorithm, using the principle of coordinate transformation of the circle spatial pretreatment; literature [9] proposed a circle polygon clipping algorithm to a single straight line and circle intersection calculations, the circle arc segment to be clipped. Existing algorithms can effectively clip the circle, but have their limitations respectively by examining from the clip complexity and algorithm validity. This paper did an investigation on the status of computer graphics, studied on the clipping around the two-dimensional graphics, and analyzed the basic algorithms of computer graphics by the method of combining theory and practice.This paper proposed a new algorithm of circle clipping against rectangular window based on encoding approach. Firstly, eight key points are calculated by the symmetry of circle. Then, the intersection relationship between the circle and the rectangular window is judged according to the encoding regulation. At last, the clipping is executed and the retained part of circle is gained. The results show that the algorithm decreases the times of complicated computations and has the character of high efficiency.