First of all entire polygon is clipped against one edge, then resulting polygon is considered, then the polygon is considered against the second edge, so on for all four edges. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. Unlike sutherland hodgman polygon clipping algorithm, this algorithm is. The problem of weiler atherton algorithm lies in clipping self intersecting polygon. Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind. This clipping procedure was developed as a method for identifying visible surfaces, and so it can be applied with arbitrary polygonclipping regions. First make a list of all intersection points namely i 1, i 2, i 3. The weiler atherton algorithm works very well for both concave and convex polygons but certain issues in case of loose polygons are left out, which are emphasized on in. Computer graphics sutherlandhodgeman polygon clipping. Program to implement sutherlandhodgeman polygon clipping. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygon arearegion. The weiler algorithm 1977 is even more complicated, but it is the one youll need if you want to clip a polygon against a nonrectangular window. Pointing technique refers to look at the items already on the screen whereas the positioning technique refers to position the item on the screen to a new position, i.
Weiler atherton clipping clockwise orientation of subject polygon 11 12 6 5 4 14 3 2. Describe the flood filling and boundary filling algorithm. The weiler atherton is a polygon clipping algorithm especially for concave polygons clipping and overcomes the downside of sutherland hodgeman. In our new algorithm a self intersecting polygon has been divided into non self intersecting contours and then perform. Clipping and other geometric algorithms mit eecs 6. Triangularization weileratherton polygon clipper lclips a subject polygon to a clip polygon lboth polygons can be of any shape lresult. The clipped scene can then be transferred to screen coordinates for final processing. In this paper a new algorithm has been proposed which can fix the problem of weiler atherton algorithm. In our new algorithm a self intersecting polygon has been divided into non self intersecting contours and then perform the weiler atherton clipping algorithm on those sub polygons. It is used in areas like computer graphics and games development where clipping of polygons is needed. Indian institute of information technology allahabad weiler atherton polygon from it 501 at international institute of information technology. Request pdf pemotongan poligon menggunakan algoritma weiler atherton polygon clipping is the important process in computer graphics applications.
Weiler atherton polygon clipping polygon clipping using nonrectangular polygon clip windows. Therefore, it may be somewhat faster when many polygon lines intersect with the clipping boundaries. Walk polygon window boundary polygons are oriented ccw. A convex polygon and a convex clipping area are given. An edge labeling approach to concave polygon clipping abstract 1. Weiler atherton polygon clipping in weiler atherton polygon clipping, the vertexprocessing procedures for window boundaries are modified so that concave polygons are displayed correctly.
Computer graphics pointing and positioning techniques. We present such an efficient algorithm for clipping arbitrary 2d polygons. Sutherlandhodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the viewing space. Weileratherton polygon clipping in weileratherton polygon clipping, the vertexprocessing procedures for window boundaries are modified so that concave polygons are displayed correctly. Polygon clipping sutherlandhodgmanpolygon clipping algorithm and weiler atherton polygon clipping algorithm. Poligon clipping sutherland hodgeman algorithm in hindi. The user indicates a position on the screen with an input device, and this position is used to insert a symbol. Weileratherton polygon the weileratherton algorithm clipper. Polygon clipping sutherlandhodgman algorithm geeksforgeeks. Generalizations of wa can be extended to complex situations, arbitrary. The weiler atherton is a polygon clipping algorithm. Search weiler atherton polygon clipping, 300 results found, polygon clipping and a classic algorithm unilateralism cutting edge.
Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping. It consider the formal mechanism for displaying views of a picture on an output device. We have two polygons p and q, vertices are given in order. Clipping any procedure which identifies that portion of a picture which is either inside or outside a picture is referred toas a clipping algorithm or clipping. Algorithms weiler atherton implementation 2d polygon. Another approach to polygon clipping no extra clipping outside window works for arbitrary shapes avoids degenerate polygons outline of weiler algorithm. Weiler atherton clipping algorithm quick reference a polygon clipping algorithm that is capable of clipping a concave polygon with interior holes to the boundaries of another concave polygon also with interior holes. Weiler atherton clipping algorithm n sutherlandhodgman required at least 1 convex polygon n weiler atherton can deal with 2 concave polygons n searches perimeter of subj polygon searching for borders that enclose a clipped filled region n finds multiple separate unconnected regions a d c b a c d b subj clip 6 5 4 3 2 b 1.
Feb 14, 2017 66 weiler atherton polygon clipping algorithm in computer graphics in hindi ugc net gate duration. Proceedings of the 4th annual conference on computer graphics and int eractive techniques, san jose. Clipping selfintersecting polygon is not considered in weileratherton. The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane.
This clipping procedure was developed as a method foridentifying visible surfaces,and so it can be applied with arbitrarypolygon clipping regions. Algorithms weiler atherton implementation 2d polygon clipping the short version. Weiler atherton polygon clipping the weiler atherton is a polygon clipping algorithm. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygonarearegion. The weiler atherton clipping algorithm is a general purpose 2d clipping algorithm. Clipping self intersecting polygon is not considered in weiler atherton algorithm and hence it is also a main disadvantage of this algorithm. For an outsidetoinside pair of vertices, fol low the polygon boundary for an insidetooutside pair of vertices, fol low the window coundary in a clockwise direction. It is thus more general, though more complex, than the sutherlandhodgman clipping. An extension of weileratherton algorithm to cope with. Explain weiler atherton polygon clipping algorithm in detail. The weiler atherton algorithm works very well for both concave and convex polygons but certain issues in case of loose polygons are left out, which are emphasized on in this paper.
The weiler atherton algorithm overcomes this by returning a set of divided polygons, but is more complex and computationally more expensive, so sutherlandhodgman is used for many rendering applications. All steps for clipping concave polygon w with a 5sided convex polygon the weileratherton algorithm overcomes this by returning a set of divided polygons, but is more complex and computationally more expensive, so sutherlandhodgman is used for many rendering applications. Polygon clipping and filling computer science department. Polygon clipping free download as powerpoint presentation. An extension of weileratherton algorithm to cope with the. An extension of weileratherton algorithm to cope with the selfintersecting polygon abstract. Hello, im am looking for a c or any other language implementation of the weiler atherton polygon clipping algorithm. Notice that the clipped polygon often will have more vertices than the unclipped one, but it can also have the same number, or less. Modification of weileratherton algorithm to address loose. I found the weiler atherton algorithm to have the most potential for general polygon cutting. Describe weiler atherton polygon clipping algorithm. The algoirthm is simple and faster that vattis 1992 algorithm, which was designed for.
This algorithm is mainly used when the cohensutherland algorithm fails when it deals with the concave polygons. If the unclipped polygon lies completely outside the clipping boundary, the clipped polygon even has zero vertices. The task is to clip polygon edges using the sutherlandhodgman algorithm. Weiler atherton algorithm when we have non convex polygons then the algorithm above might produce polygons with coincident edges this is sometimes ok for rendering but is not for other applications e. This seems nontrivial it gets asked quite a lot on various forums, but i absolutely need this as a building block for a more complex algorithm. A polygon clipping algorithm that is capable of clipping a concave polygon with interior holes to the boundaries of another concave polygon also with interior holes. Consider each edge e of clipping area and do following. Pdf an extension of weileratherton algorithm to cope.
In geometry a polygon is a flat shape consisting of straightlines that are joined to form a circuit. Section 4 begins the design process for a hardwaresoftware codesigned imple mentation of the weileratherton polygon clipping algorithm. I found a discussion of it in the foley van dam interactive computer graphics book, but no code, not even psuedocode. This clipping procedure was developed as a method for identifying visible surfaces, and so it can be applied with arbitrary polygon clipping regions. In my opinion it would make more sense to have a standalone function that takes a clipping polygon and a polygon to draw and returns the clipped collection of polygons. The weiler atherton algorithm weiler and atherton, 1977, the vatti algorithm vatti, 1992, and the greinerhorman algorithm greiner and hormann, 1998 are three acknowledged polygon clipping.
Modelling complex shapes parametric polynomial curves weileratherton polygon clipper. An extension of weiler atherton algorithm to cope with the selfintersecting polygon abstract. Weiler atherton algorithm we use this algorithm to find union or intersection of not crossed polygons we have two polygons p and q, vertices are given in order 1 we calculate intersections of sides and put them in two lists. Weiler and atherton, and by sechrest and greenberg can deal with polygons. Design, verification and implementation of a polygon clipping. It is used in the areas like computer graphics, games development and others where clipping of polygon is needed. Pemotongan poligon menggunakan algoritma weiler atherton. Modification of weileratherton algorithm to address. Triangularization weiler atherton polygon clipper lclips a subject polygon to a clip polygon lboth polygons can be of any shape lresult. For a twodimensional picture, a view is selected by specifying a subarea of the total picture area. Indian institute of information technology allahabad. It is performed by processing the boundary of polygon against each window corner or edge. Follow a path that may be a polygon edge or a window boundary, depending on the type of edge 1. Clipping polygons n cohensutherland and liangbarsky clip line segments against each window in turn n polygons can be fragmented into several polygons during clipping n may need to add edges n need more sophisticated algorithms to handle polygons.
The algorithm can handle arbitrary closed polygons, specifically where the clip and subject polygons may selfintersect. Contribute to yinyanghuopengl development by creating an account on github. Weileratherton clipping algorithm oxford reference. In other words, just make getclippedpolygon a standalone function. Input is in the form of vertices of the polygon in clockwise order. While most clipping algorithms are optimized for a rectangular clipping region, the wieler atherton algorithm can use simple polygons for both the subject of the clipping as well as the actual clipping region itself.
An extension of weileratherton algorithm to cope with the 1. Hello, i am implementing the weiler atherton algorithm as it really matches my n eeds for some physic dev. Feb 25, 2018 the weiler atherton algorithm of polygons clipping has been cited in a lot of tutorials. Introduction cyrusbeck clipping algorithm cohensutherland clipping algorithm polygon clipping sutherlandhodgman clipping algorithm weiler atherton clipping algorithm. Indian institute of information technology allahabad weiler. Weiler atherton polygon clipping free open source codes. The idea seemed fine and simple but as for coding implementation, it is not so easy. Replace crossing points with vertices form linked lists of edges change links at vertices enumerate polygon patches weileratherton polygon clipping. Weiler atherton polygon clipping algorithm geeksforgeeks. The problem of weiler atherton algorithm lies in clipping selfintersecting polygon.
The weileratherton clipping algorithm is a general purpose 2d clipping algorithm. The viewing transformation is insensitive to the position of points relative to the viewing volume. Mar 04, 2014 clipping self intersecting polygon is not considered in weiler atherton algorithm and hence it is also a main disadvantage of this algorithm. Weiler atherton polygon clipping algorithm duration. An extension of polygon clipping to resolve degenerate. Weiler atherton polygon clippingin this algorithm,the vertex processing procedures for windowboundaries are modified so that concave polygons are displayedcorrectly.