Sutherland and hodgman 6 introduce reentrant polygon clipping. Polygon clipping and polygon reconstruction lehrgebiet. An efficient algorithm for line and polygon clipping springerlink. Sutherland hodgman algorithm p0 p1 clip the polygon against each boundary of the clip region successively result is possibly null if polygon is outside can be generalised to work for any polygonal clip region, not just rectangular. The algorithm proceeds in stages by passing each clipped polygon to the next edge of the windows and clipping. Clipping algorithm in computer graphics linkedin slideshare. Jun 19, 2016 2c using the previously generated polygon, repeat the sutherland hodgman algorithm to the right reference plane. The algorithm demonstrates the practicality of various ideas from computational geometry. Then draw a rectangular screen area, so that parts of the polygon are outside this area. First make a list of all intersection points namely i 1, i 2, i 3. A region code is a 4 digit bit code which indicates one of nine regions having the end point of. Program to show the implementation of cohen sutherland line clipping algorithm. The task is to clip polygon edges using the sutherlandhodgman algorithm.
The laingbarsky algorithm 1983 is a good deal more complicated, but in certain cases fewer intersections need to be calculated than for sutherland hodgman. The oldest one from 1974 is called the sutherlandhodgman algorithm. What is sutherlandhodgman polygon clipping algorithm in. Among which, the sutherlandhodgman 19, vatti 20, and greinerhormann 7 algorithms are the most representative when dealing with arbitrary polygon clippings. In geometry a polygon is a flat shape consisting of straightlines that are joined to form a circuit. Clip a polygon by successively clipping against each infinite clip edge after each clipping a new set of vertices is produced. It spendsologp time on each edge of the clipped polygon, wherep is the number of window edges, while the sutherlandhodgman algorithm spendsop time. It uses 2d polygon clipping to render images in 3d by removal of hidden surfaces. Polygon clipping background theory computer science. I am writing a program that creates a polygon that is shaped like a fish and fills it with green. That article explains the algorithm and it also explains the code. Hello friends, i am free lance tutor, who helped student in completing their homework.
Sutherland hodgman polygon clipping algorithm author. Sutherlandhodgman algorithm p0 p1 clip the polygon against each boundary of the clip region successively result is possibly null if polygon is outside can be generalised to work for any polygonal clip region, not just rectangular. In polygon clipping, we use an algorithm that generates one or more closed areas that are then scan converted for the appropriate area fill. The sutherland and hodgmans polygon clipping algorithm is used in this tool. Sutherland hodgman polygon clipping algorithm right clip boundary bottom clip boundary left clip boundary top clip boundary idea.
Sutherland hodgeman polygon clipping algorithm is used for polygon clipping. Sutherlandhodgeman polygon clipping algorithm c program. Sutherlandhodgman polygon clipping you are encouraged to solve this task according to the task description, using any language you may know. 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. Poligon clipping sutherland hodgeman algorithm in hindi.
Apr 05, 20 sutherland hodgman algorithm each edge of the polygon must be testedagainst each edge of the clip rectangle. May 30, 2014 a simple video that explains the working of sutherland hodgman polygon clipping algorithm in detail. Consider the concave polygon in the picture below by just clipping the lines it is divided in several separate polygons. It works by extending each line of the convex clip polygon in turn and selecting. Program of cohen sutherland line clipping algorithm. Next, one side of the clip polygon is extended infinitely in both directions, and the path of the subject polygon is traversed. Polygon clipping ppt polygon convex set free 30day.
Clipping polygons the sutherland hodgman algorithm clipping polygons would seem to be quite complex. A convex polygon and a convex clipping area are given. It accepts an ordered sequence of verices v1, v2, v3. It spendsologp time on each edge of the clipped polygon, wherep is the number of window edges, while the sutherland hodgman algorithm spendsop time per edge.
A polygon can also be clipped by specifying the clipping window. Sutherlandhodgman algorithm each edge of the polygon must be testedagainst each edge of the clip rectangle. There are buttons to move the this fish around inside of a window. The algorithm you present is not the sutherland hodgman algorithm for clipping against an arbitrary polygon, but the cohen sutherland algorithm for clipping against a rectangular viewport. An implementation of the sutherlandhodgman algorithm used for clipping polygons in c. 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. Poligon clipping sutherland hodgeman algorithm in hindi computer graphics. Sutherland hodgeman polygon clipping this program is for implementing sutherland hodgeman polygon clipping. Mathematically, clipping can be described using the terminology of constructive geometry. We can correctly clip a polygon by processing the polygon boundary as whole each window edge. Video explains with help of an example the working of the algorithm. It solves a series of simple and identical problems that, when combined, solve the overall problem. To associate your repository with the polygonclippingalgorithm topic, visit. It is performed by processing the boundary of polygon against each window corner or edge.
The task is to clip polygon edges using the sutherland hodgman algorithm. Midpoint subdivision line clipping algorithm 1 read two end points of line p1 x1,y1 and p2 x2,y2. Polygon clipping not working when using sutherlandhodgman. Php polygon clipping using the sutherlandhodgman algorithm.
Im struggling to find a good, working implementation of the sutherlandhodgman algorithm for clipping one polygon by the edges of another polygon. Basic conceptstypes of graphics devices, display file structure, display file interpreter, display processors, graphics file format, bmp, tiff, pcx, gif. The sutherland hodgman algorithm performs a clipping of a polygon against each window edge in turn. It does so by using a 4 bit code called as region code or outcodes. The sutherland hodgeman polygon clipping algorithm slideshare. This algorithm applies to convex, planar or nonplanar polygons. Mar 20, 2015 polygon clipping algorithm by sutherland and hodge.
Visualizing the sutherland hodgman algorithm harold serrano. Windowing and clipping viewing transformation, 2d clipping, sutherlandcohen, subdivision line clipping algorithm, midpoint subdivision algorithm, generalized clipping, cyrusbeck algorithm, interior and exterior clippingpolygon clipping, sutherlandhodgman algorithm. Sutherlandhodgeman polygon clipping this program is for implementing sutherlandhodgeman polygon clipping. We need an organized way to dealwith all these cases. The nichollleenicholl nln, liangbarsky lb, an improved implementation of the cohensutherland cs, and sutherlandhodgman sh algorithms are compared for 2d. Sutherlandhodgeman polygon clipping programs and notes. This paper presents a new 2d polygon clipping method, based on an extension to the sutherlandcohen 2d line clipping method. We now summarize the three most popular algorithms for performing polygon clipping. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window. There are several wellknown polygon clipping algorithms, each having its strengths and weaknesses. Line and circle generationline generation dda and bresenhams algorithm, thick line segments, antialising of lines, circle generation dda and bresenhams algorithm, character generation. This paper presents a new 2d polygon clipping method, based on an extension to the sutherland cohen 2d line clipping method.
Disadvantages of sutherland hodgman polygon clipping. The sutherlandhodgman algorithm clips a polygon against all edges of the clipping region in turn. Sutherland and hodgmans polygonclipping algorithm uses a divideandconquer strategy. This is one of the oldest and most popular line clipping algorithm. Reentrant polygon clipping communications of the acm. Grab a piece of paper, and draw a convex polygon on it. Consider each edge e of clipping area and do following. We present an algorithm for clipping a polygon or a line against a convex polygonal window. Sutherland hodgman algorithm contd the algorithm clips every polygon edge against each clipping line use an output list to store newly clipped polygon vertices with each polygon edge, 1 or 2 vertices are added to the output list s p. Sutherland hodgman polygon clipping university of helsinki. This is achieved by processing all polygon vertices against each clip rectangle boundary in turn.
Sutherlandhodgeman polygon clipping programs and notes for mca. The simple problem is to clip a polygon against a single infinite clip edge. Theoretical and experimental analyses show that the. 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. The input polygons are always quads that consist of four points. The sutherland hodgman algorithm is a wellknown algorithm for clipping a polygon against a rectangle. An algorithm that clips a polygon is rather complex. Program to implement sutherlandhodgeman polygon clipping. I have 4 years of hands on experience on helping student in completing their homework. Polygon clipping algorithm by sutherland and hodge. Multiplepolygons may result from clipping a singlepolygon.
Clipping polygons the sutherlandhodgman algorithm clipping polygons would seem to be quite complex. Php polygon clipper using the sutherlandhodgman algorithm. To speed up the process this algorithm performs initial tests that reduce number of intersections that must be calculated. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. Clipping, in the context of computer graphics, is a method to selectively enable or disable rendering operations within a defined region of interest. Easy tutor author of program of sutherland hodgemann algorithm for polygon clipping is from united states. Php polygon clipping using the sutherland hodgman algorithm clip. Sutherlandhogson polygon clipping javascript github. Input is in the form of vertices of the polygon in clockwise order. May 19, 2011 sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. The polygons in this algorithm are defined regarding their vertices only, not edges. Therefore, it may be somewhat faster when many polygon lines intersect with the clipping boundaries.
The algorithm steps from vertex to vertex, adding 0. This algorithm is based on a divideandconquer strategy that solves a series of simple and identical problems that, when combined, solve the overall problem. Vertices from the input list are inserted into an output list if they lie on the visible side of the. Polygon clipping is one of those humble tasks computers do all the time. Oct 16, 2012 clipping algorithm in computer graphics 1. Polygon clipping sutherlandhodgman algorithm geeksforgeeks. Weiler atherton polygon clipping algorithm geeksforgeeks. The algorithm you present is not the sutherlandhodgmanalgorithm for clipping against an arbitrary polygon, but the cohensutherlandalgorithm for clipping against a rectangular viewport. I wrote a php implementation of the polygon clipping algorithm by sutherlandhodgman. Midpoint subdivision line clipping algorithm teczzers. Sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Concerning surfacesurface clipping, maillot proposed a clipping algorithm based on the sutherlandhodgman polygon to clip the triangles strip by the plane in the reference, and lindenbeck et al.
Program to illustrate the implementation of 3d rotation transformation along. A working implementation of the sutherlandhodgman algorithm. Its a basic operation in creating graphic output of all kinds. Explain sutherland hodgeman algorithm for polygon clipping. A scene is made up of a collection of objectsspecified in world coordinates world coordinates 3. The sutherland hodgeman polygon clipping algorithm. 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. A single polygon can actually be split into multiple polygons can you draw an example. Program to show the implementation of sutherland hodgeman polygon clipping. It works by extending each line of the convex clip polygon in turn and selecting only vertices from the subject polygon that are on the visible side.
The code snippet seems to be taken directly from the corresponding wikipedia article. Polygon clipping and filling computer science department. The output of a polygon clipper should be a sequence of vertices that define the clipped polygon boundaries. Pdf polygon clipping is an important operation that computers. Sutherland hodgman polygon clipping algorithm pracspedia. A rendering algorithm only draws pixels in the intersection between the clip region and the scene model. Weileratherton polygon clipping convex polygons are correctly clipped by the sutherlandhodgman algorithm, but concave polygons may be displayed with extra areas area inside the red circle, as demonstrated in the following figure. In the second instance, no points are saved since they both lie on the back of the plane.
More generic clipping algorithm, both the polygon to be clipped and the polygon. Program of sutherland hodgemann algorithm for polygon clipping. More than 50 million people use github to discover, fork, and contribute to over 100 million projects. A precise tin clipping algorithm taking into account of.
These algorithms are able to clip polygons against irregular convex planefaced. Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind. This is a part of mumbai university mca colleges computer graphics cg mca sem 2. Polygon clipping algorithm by sutherland and hodgeman c. Sutherlandhodgman algorithm handles in a suboptimal way. Pdf polygon clipping and polygon reconstruction researchgate. Sutherlandhodgeman polygon clipping ecomputernotes. In the first case, p1 is in front of the plane and p2 is on the back.
I want to have only the parts of the fish that are inside of the window to be visible so i am attempting to implement the. The sutherlandhodgmanalgorithm is a wellknown algorithm for clipping a polygon against a rectangle. Computer graphics sutherlandhodgeman polygon clipping. First the polygon is clipped against the left edge of the polygon window to get new vertices of the.
Clip polygon pto clipping edge foreachedge in polygon p check clipping cases there are 4 case 1. The sutherland hodgman algorithm clips a polygon against all edges of the clipping region in turn. An efficient algorithm for line and polygon clipping. The sutherlandhodgman algorithm is an algorithm used for clipping polygons.
I also guide them in doing their final year projects. Polygon clipping free download as powerpoint presentation. Sutherlandhodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the viewing space. Feb 14, 2017 poligon clipping sutherland hodgeman algorithm in hindi computer graphics. To accomplish this task, it is not enough to clip the lines one by one with e.
Windowing conceptsclipping introduction brute force cohen sutherland clipping algorithmarea clipping sutherland hodgman area clipping algorithm 2. A machineindependent comparison of several 2d and 3d line segment clipping algorithms is presented. Thus, an intersection point is calculated and saved. The sutherland hodgman algorithm is used for clipping polygons. After discussing three basic polygon clipping algorithms, a different approach is proposed, explaining the principles of a new algorithm and presenting it step by step. Polygon clipping algorithm by sutherland and hodgeman c program. Clip polygon pto clipping edge foreachedge in polygon p. It spendsologp time on each edge of the clipped polygon, wherep is the number of window edges, while the sutherlandhodgman algorithm spendsop time per edge.
1245 664 46 1472 297 585 1250 260 213 797 295 945 354 1235 498 1254 825 601 483 968 74 1001 1147 607 520 357 1387 1176 285 1178 1331 996 1454 565 162