This paper presents a new algorithm for line clipping against a polygonal window by exploiting the local relationship between each line segment and the polygon. Firstly, a minimal enclosing box （MEB） of the polygon ...This paper presents a new algorithm for line clipping against a polygonal window by exploiting the local relationship between each line segment and the polygon. Firstly, a minimal enclosing box （MEB） of the polygon is adopted to reject the invisible line segments located outside the MEB. Secondly, a 45° rotated box is used to encode the endpoint of the line segment, and then reject a portion of the invisible segments crossing polygon comers. Finally, instead of encoding the endpoints of all line segments with respect to the polygonal window, each vertex of the polygon is encoded, taking the line segment to be clipped as reference. For efficient encoding of the polygon vertices, a new concept, termed with slope adaptive virtual box, is introduced regarding each line segment. Such a box can not only conveniently reject all totally invisible lines lying outside the MEB conveniently, but also precisely identify the edges of the polygon with which the line segment potentially intersects. With the summation of the vertex codes, it can be verified whether the line segment is separated from or potentially intersects the polygon window. Based on the product of the codes of adjacent vertices, singular cases of intersection can be solved accurately. Experimental results demonstrate the efficiency and stability of the new algorithm.展开更多
Line segment clipping is a basic operation of the visualization process in computer graphics. So far there exist four computational models for clipping a line segment against a window, (1) the encoding, (2) the parame...Line segment clipping is a basic operation of the visualization process in computer graphics. So far there exist four computational models for clipping a line segment against a window, (1) the encoding, (2) the parametric, (3) the geometric transformation, and (4) the parallel cutting. This paper presents an algorithm that is based on the third method. By making use of symmetric properties of a window and transformation operations, both endpoints of a line segment are transformed, so that the basic cases are reduced into two that can be easily handled, thus the problems in NLN and AS where there are too many sulyprocedure calls and basic cases that are difficult to deal with are tackled. Both analytical and experimental results from random input data show that the algorithm is better than other developed ones, in view of the speed and the number of operations.展开更多
基金Project supported by the National Natural Science Foundation of China(No. 60021201), and the Research Fund for the Doctoral Program of Higher Education (No. 2002335093), China
文摘This paper presents a new algorithm for line clipping against a polygonal window by exploiting the local relationship between each line segment and the polygon. Firstly, a minimal enclosing box （MEB） of the polygon is adopted to reject the invisible line segments located outside the MEB. Secondly, a 45° rotated box is used to encode the endpoint of the line segment, and then reject a portion of the invisible segments crossing polygon comers. Finally, instead of encoding the endpoints of all line segments with respect to the polygonal window, each vertex of the polygon is encoded, taking the line segment to be clipped as reference. For efficient encoding of the polygon vertices, a new concept, termed with slope adaptive virtual box, is introduced regarding each line segment. Such a box can not only conveniently reject all totally invisible lines lying outside the MEB conveniently, but also precisely identify the edges of the polygon with which the line segment potentially intersects. With the summation of the vertex codes, it can be verified whether the line segment is separated from or potentially intersects the polygon window. Based on the product of the codes of adjacent vertices, singular cases of intersection can be solved accurately. Experimental results demonstrate the efficiency and stability of the new algorithm.
文摘Line segment clipping is a basic operation of the visualization process in computer graphics. So far there exist four computational models for clipping a line segment against a window, (1) the encoding, (2) the parametric, (3) the geometric transformation, and (4) the parallel cutting. This paper presents an algorithm that is based on the third method. By making use of symmetric properties of a window and transformation operations, both endpoints of a line segment are transformed, so that the basic cases are reduced into two that can be easily handled, thus the problems in NLN and AS where there are too many sulyprocedure calls and basic cases that are difficult to deal with are tackled. Both analytical and experimental results from random input data show that the algorithm is better than other developed ones, in view of the speed and the number of operations.
