A polygon clipper takes as input thevertices of a polygon and returns oneor morepolygons. The task is to clip polygon edges using the sutherlandhodgman algorithm. 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. Weiler atherton polygon clipping search and download weiler atherton polygon clipping open source project source codes from. Computer graphics assignment help, polygon or area clipping algorithm, polygon or area clipping algorithm sutherlandhodgman algorithm there are different algorithms as liangbarsky, line clipping, weileratherton polygon clipping, which are fairly efficient in performing the job of clipping images. The weiler atherton is a polygon clipping algorithm. Atherton algorithm fails to generate the desired results.
In geometry a polygon is a flat shape consisting of straightlines that are joined to form a circuit. Weiler atherton polygon clipping free open source codes. A polygonclipping algorithm that is capable of clipping a concave polygon with interior holes to the boundaries of another concave polygon also with interior holes. Input is in the form of vertices of the polygon in clockwise order. Pdf polygon clipping is an important operation that computers,execute all the time. The experiment shows that weiler atherton algorithm is slower than sutherland hodgeman algorithm, but the advantage is this algorithm can calculate the clipping process that creating more than one. The primary use of clipping in computer graphics is to remove objects, lines, or line segments that are outside the viewing pane. Clipping self intersecting polygon is not considered in weiler atherton algorithm and hence it is also a main disadvantage of this algorithm. In this paper a new algorithm has been proposed which can fix the problem of weiler atherton algorithm. Polygon clipping sutherlandhodgmanpolygon clipping algorithm and weiler atherton polygon clipping algorithm. Clipping selfintersecting polygon is not considered in weileratherton algorithm and. Sutherlandhodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the viewing space.
Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind. Clipping point clipping line clipping midpoint subdivision algorithm text clipping polygon sutherlandhodgeman polygon clipping weileratherton polygon clipping. It is performed by processing the boundary of polygon against each window corner or edge. Polygon clipping is a process in which we only consider the part which is inside the view pane or window. Clipping and other geometric algorithms mit eecs 6. How to distinguish between an inbound and an outbound edge of a polygon. Which path we follow depends on the polygonprocessing direction clockwise or counterclockwise and whether the pair of. The sutherlandhodgman clipping algorithm finds the polygon that is the intersection between an arbitrary polygon the subject polygon and a convex polygon the clip polygon. Polygon clippingcollection of connected lines is considered aspolygon. Weileratherton clipping clockwise orientation of subject polygon 11 12 6 5 4 14 3 2. It seems like finding inbound edges invole another huge algorithm and thereby affects the efficiency of. 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. A closed polygon when clipped cthen we may get one or more open c d polygon or dlines.
The sutherlandhodgman algorithm clips a polygon against all edges of the clipping region in turn. Form linked lists of edges change links at vertices enumerate polygon patches weileratherton polygon clipping. The vertexprocessing procedures for window boundaries are modified so that concave polygon is displayed. Weileratherton polygon clipping this algorithm works with either convex or concave regions. The viewing transformation is insensitive to the position of points relative to the viewing volume. Computer graphics sutherlandhodgeman polygon clipping.
It is thus more general, though more complex, than the. The algorithm steps from vertex to vertex, adding 0. Weileratherton clipping algorithm oxford reference. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygon arearegion. Computer graphics weileratherton polygon clipping javatpoint. The algorithm terminates when the entire border of the original subject polygon has been traced exactly once. Search weiler atherton codebus is the largest source code and program resource store in internet. If this is for offline processing, use arbitrary precision arithmetic to eliminate a major source of accuracy errors. It is used in the areas like computer graphics, games development and others where clipping of polygon is needed. Clipping polygons the sutherlandhodgman algorithm clipping polygons would seem to be quite complex. Background weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible.
An extension of weileratherton algorithm to cope with the selfintersecting polygon abstract. It is used in computer graphics especially 2d graphics to reduce the complexity of a scene being displayed by eliminating parts of a polygon that do not. Polygon clipping sutherlandhodgmanpolygon clipping algorithm and weileratherton polygon clipping algorithm. While most clipping algorithms are optimized for a rectangular clipping region, the wieleratherton algorithm can use simple polygons for both the subject of the clipping as well as the actual clipping region itself. Weileratherton polygon the weileratherton algorithm clipper. This algorithm can also be used to identify visible surfaces in 3d.
I found a discussion of it in the foley van dam interactive computer graphics book, but no. Weiler atherton polygon clipping algorithm avi clipping dxf algorithm edge clipping midi clipping polygon maker union polygon using aes algorithm code 120 of 60 pages. Consider each edge e of clipping area and do following. How to describe the bidirectional links for the weiler. Contribute to yinyanghuopengl development by creating an account on github. Bsp based clipping is no better than the weileratherton algorithm in. The problem of weiler atherton algorithm lies in clipping self intersecting polygon. 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. An extension of weileratherton algorithm to cope with the.
It will be slow, but the alternative is manually examining thousands of failure cases. 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. Whenever an edge takes us outside the clip region we take a. When an edge of a candidatesubject polygon exits the clipping area, save the intersection point and follow the clipping polygon. Rust realisation of weiler atherton clipping algorithm. The problem of weileratherton algorithm lies in clipping selfintersecting polygon. Weileratherton algorithm in 3d codes demo implementation. We will remove or clip the part that is outside the window. Polygon or area clipping algorithm, computer graphics. Modification of weileratherton algorithm to address loose. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping.
Let us pass it through the generalized algorithm stated above, it is found that it is a case of the surrounding polygon and hence modified weileratherton algorithm needs to be applied. Weileratherton polygon clipping the basic idea in this algorithm is that instead of always proceeding around the polygon edges as vertices are processed, we sometimes want to follow the window boundaries. Weiler atherton polygon clipping algorithm geeksforgeeks. Sutherlandhodgman algorithm clip polygon boundary against the four edges of the window separately clip left clip top. The idea is to go around edges of the figure in clockwise or counterclockwise order. Walk polygonwindow boundary polygons are oriented ccw mit eecs 6.
Sutherlandhodgman polygon clipping algorithm thanks again for watching. A single polygon can actually be split into multiple polygons can you draw an example. The weileratherton algorithm promises to offer all these features, but every time i sit down with it, i get hung up on implementing the basic constructs. Download weiler atherton polygon clipping algorithm source. We will use the following algorithms for polygon clipping sutherlandhodgeman polygon clipping algorithm. Weiler atherton clipping algorithm is a polygon clipping algorithm. Explain weiler atherton polygon clipping algorithm in detail. Often, it is possible to feed a weird polygon to an algorithm and retrieve an incorrect result. The weileratherton algorithm of polygons clipping in 2d may be briefly described as follows to find all the points and segments of. Algorithms weiler atherton implementation 2d polygon clipping the short version.
Specifically it requires making bidirectional associations between nodes which can then be traversed in either direction. The weileratherton clipping algorithm is a general purpose 2d clipping algorithm. When the clipped polygons have two or more separate sections, then it is the concave polygon handled by this algorithm. It is used in areas like computer graphics and games development where clipping of polygons is needed. For example, we can find the intersecting points separately and then find for. Pemotongan poligon menggunakan algoritma weiler atherton. Program to implement sutherlandhodgeman polygon clipping. Sutherlandhodgman polygon clipping algorithm youtube. A convex polygon and a convex clipping area are given. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygonarearegion.
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