Clip a polygon by successively clipping against each infinite clip edge after each clipping a new set of vertices is produced. Sutherlandhodgman polygon clipping algorithm youtube. The task is to clip polygon edges using the sutherlandhodgman algorithm. In polygon clipping, we use an algorithm that generates one or more closed areas that are then scan converted for the appropriate area fill. There are 4 rules explained in sutherlandhodgman algorithm for clipping polygons. Sutherlandhodgman filled polygon clipping it might appear that we can solve polygon clipping by just using line clipping on the edges, but unfortunately this doesnt work. Vertices from the input list are inserted into an output list if they lie on the visible side of the. If you liked it pls make it a point to comment below. First make a list of all intersection points namely i 1, i 2, i 3.
The algorithm to perform sutherland hodgeman clipping is very simple and easy to implement. I have 4 years of hands on experience on helping student in completing their homework. Write advantages of sutherlandhodgman polygon clipping. Sutherland hodgman polygon clipping algorithm right clip boundary bottom clip boundary left clip boundary top clip boundary idea. Sutherland hodgeman polygon clipping this program is for implementing sutherland hodgeman polygon clipping. Computer graphics clipping cohen sutherland algorithm line cyrusback. In geometry a polygon is a flat shape consisting of straightlines that are joined to form a circuit. Clipping polygons the sutherland hodgman algorithm clipping polygons would seem to be quite complex. This is a part of mumbai university mca colleges computer graphics cg mca sem 2. Sutherlandhodgeman polygon clipping ecomputernotes. In vertexarray is the array of input polygon vertices.
The viewing pipeline, viewing coordinate reference frame, window to viewport coordinate transformation, viewing functions, cohensutherland and cyrusbeck line clipping algorithms, sutherland hodgeman polygon clipping algorithm. Sutherland hodgman polygon clipping algorithm thanks again for watching. Application of sutherland hodgman polygon clipping. The code snippet seems to be taken directly from the corresponding wikipedia article. This program is for implementing sutherlandhodgeman polygon clipping. The sutherlandhodgman algorithm is an algorithm used for clipping polygons.
To accomplish this task, it is not enough to clip the lines one by one with e. The algorithm you present is not the sutherlandhodgmanalgorithm for clipping against an arbitrary polygon, but the cohensutherlandalgorithm for clipping against a rectangular viewport. A new algorithm for computing boolean operations on polygons. Line clipping algorithms cohen sutherland line clipping algorithm 2. More general algorithms were presented in 1, 6, 8, 9. Thus, an intersection point is calculated and saved. A polygon clipper takes as input the vertices of polygon and return one or more polygon.
The weileratherton is a polygon clipping algorithm especially for concave polygons clipping and overcomes the downside of sutherland hodgeman. We can use sutherlandhodgman algorithm for polygon clipping. Many efficient algorithms exist for polygon clipping foley et al. A polygon can also be clipped by specifying the clipping window. Implementation of polygon clipping using sutherlandhodgeman algorithm with source code in. The simple problem is to clip a polygon against a single infinite clip edge. Namun hal ini tidak menjadikan clipping pada polygon dapat menggunakan algoritma yang sama seperti pada clipping garis, karena pada kondisikondisi tertentu algoritma clipping garis seperti cohensutherland tidak dapat diterapkan. The output of a polygon clipper should be a sequence of vertices that define the clipped polygon boundaries. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window. The sutherland hodgman algorithm performs a clipping of a polygon against each window edge in turn.
The weileratherton algorithm overcomes this by returning a set of divided polygons, but is more complex and computationally more expensive, so sutherland hodgman is used for many rendering applications. Grab a piece of paper, and draw a convex polygon on it. Consider each edge e of clipping area and do following. Clipping polygons the sutherlandhodgman algorithm clipping polygons would seem to be quite complex. The oldest one from 1974 is called the sutherlandhodgman algorithm. A convex polygon and a convex clipping area are given. That of liang and barsky 5require that the clip polygon be rectangular. If both vertices are inside the clipping area save the second.
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. May 07, 2017 in this video we will learn sutherland hodgeman polygon clipping algorithm. If we clip its edges they will disappear, and the polygon will vanish. Contains a subject wise list of programs which students find in engineering courses. Input is in the form of vertices of the polygon in clockwise order. Then draw a rectangular screen area, so that parts of the polygon are outside this area. Clipping polygon sama dengan clipping garis karena polygon pada dasarnya tersusun dari garisgaris yang ujungujungnya saling bertemu. It works by extending each line of the convex clip polygon. The output of a polygon clipper should be a sequence of vertices that defines the clipped polygon boundaries. Visualizing the sutherland hodgman algorithm harold serrano.
Top left and bottom right coordinates of the clipping window. Line clipping against non rectangular clip windows 4. The sutherland hodgman algorithm is a wellknown algorithm for clipping a polygon against a rectangle. Computer graphics sutherlandhodgeman polygon clipping. Clip single polygon using single infinite clip edge repeat 4. Sutherland hodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the viewing space. The following example illustrate a simple case of polygon clipping. If the first vertex is inside and the second is outside compute the intersection with the border of the clipping area and save it. Its a basic operation in creating graphic output of all kinds.
Sutherlandhodgman polygon clipping pseudo code for sutherl. Home computer graphics program to implement sutherlandhodgeman polygon clipping algorithm program to implement sutherlandhodgeman polygon clipping algorithm may 11, 2011 vaibhavwp leave a comment go to comments. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. It steps from vertex to vertex and adds 0, 1, or 2 vertices at each step to the output list. We can correctly clip a polygon by processing the polygon boundary as whole each window edge. Sutherlandhodgeman polygon clipping programs and notes for mca. Hello friends, i am free lance tutor, who helped student in completing their homework.
May 19, 2011 sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Implement polygon clipping using sutherlandhodgeman. We push the first 1 to a 0 by clipping against the line y max 6. Sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Sutherlandhodgeman clipping the sutherlandhodgeman triangle clipping algorithm uses a divideandconquer strategy. The sutherlandhodgman algorithm clips a polygon against all edges of the clipping region in turn. 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. It accepts an ordered sequence of verices v1, v2, v3. Sutherland hodgman polygon clipping algorithm subproblem. For polygon clipping, we require an algorithm that will generate one or more closed areas that are then scan converted for the appreciate area fill. A single polygon can actually be split into multiple polygons can you draw an example. That article explains the algorithm and it also explains the code. A polygon can be clipped by processing its boundary as a whole against each window edge. A closed polygon when clipped then we gets one or more open polygon or lines.
Sutherland hodgeman polygon clipping algorithm in this algorithm. There are 4 rules explained in sutherland hodgman algorithm for clipping polygons. Using this program clip the polygon against the rectangular window. For clipping cd, we start with d since it is outside the window.
The algorithm steps from vertex to vertex, adding 0. Sutherland hodgman polygon clipping algorithm author. Computer graphics assignment help, application of sutherland hodgman polygon clipping, for good understanding of the application of the rules specified above see the following figure, where the shaded region demonstrates the clipped polygon. 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. Sutherland hodgman polygon clipping algorithm pracspedia. Disadvantages of sutherland hodgman polygon clipping algorithm. First of all entire polygon is clipped against one edge, then resulting polygon is considered, then the polygon is considered against the. It solves a series of simple and identical problems that, when combined, solve the overall problem. Each edge of the polygon must be tested against each edge of the clip rectangle. Explain sutherland hodgeman algorithm for polygon clipping. Program to show the implementation of sutherlandhodgeman.
More than 50 million people use github to discover, fork, and contribute to over 100 million projects. It clips a polygon against all edges of the clipping region. Polygon clipping sutherland hodgman algorithm a polygon can also be clipped by specifying the clipping window. The sutherland hodgman algorithm clips a polygon against all edges of the clipping region in turn. Sutherlandhodgman polygon clipping you are encouraged to solve this task according to the task description, using any language you may know. Clip polygon pto clipping edge foreachedge in polygon p check clipping cases there are 4 case 1. First the polygon is clipped against the left edge of the polygon window to get new vertices of the. Sutherlandhodgeman polygon clipping programs and notes. Polygon clipping is one of those humble tasks computers do all the time.
Program to implement sutherlandhodgeman polygon clipping. Sutherlandhodgeman polygon clipping algorithm c program. The sutherland hodgman algorithm is used for clipping polygons. An implementation of the sutherlandhodgman algorithm used for clipping polygons in c.
I wrote a php implementation of the polygon clipping algorithm by sutherlandhodgman. I also guide them in doing their final year projects. Php polygon clipping using the sutherlandhodgman algorithm. Modification of weileratherton algorithm to address loose. Sutherland hodgeman polygon clipping algorithm is used for polygon clipping. In the first case, p1 is in front of the plane and p2 is on the back. Easy tutor author of program to show the implementation of sutherlandhodgeman polygon clipping algorithm is from united states. Polygon clipping sutherlandhodgman algorithm geeksforgeeks. 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. There are several wellknown polygon clipping algorithms, each having its strengths and weaknesses. Polygon clipping sutherland hodgman algorithm way2techin. Polygon clipping algorithm by sutherland and hodgeman c. Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind.
It is performed by processing the boundary of polygon against each window corner or edge. 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. This is achieved by processing all polygon vertices against each clip rectangle boundary in turn. Weileratherton clipping algorithm n sutherlandhodgman required at least 1 convex polygon n weileratherton 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. Next, one side of the clip polygon is extended infinitely in both directions, and the path of the subject polygon is traversed. Php polygon clipping using the sutherland hodgman algorithm clip.
The resulting intersection i 3 is,6,and its code is 0000. Thus i3 d is clipped and the remaining segment ci3. Weiler atherton polygon clipping algorithm geeksforgeeks. The oldest one from 1974 is called the sutherland hodgman algorithm. 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. Sutherland and hodgemans algorithm 10is limited to convex clip polygons. Clipping points, lines, and polygons in aligned rectangular.
Sutherlandhodgman polygonclipping algorithm right clip boundary bottom clip boundary left clip boundary top clip boundary idea. Mar 20, 2015 polygon clipping algorithm by sutherland and hodge. However, most of them are limited to certain types of polygons, for instance, andereev 1989 and sutherland and hodgeman 1974 algorithms require a convex clip polygon, while the algorithm by liang and barsky 1983 requires a rectangular clip polygon. Sutherland and hodgmans polygon clipping algorithm uses a divideandconquer strategy. This is a part of mumbai university mca colleges computer graphics. Computer graphics notes pdf cg notes pdf smartzworld. Jun 19, 2016 2c using the previously generated polygon, repeat the sutherland hodgman algorithm to the right reference plane. A description with examples for the sutherlandhodgman polygon clipping algorithm. Sutherlandhodgman polygon clipping algorithm thanks again for watching. Background weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. A simple subproblem is to clip a polygon against the single clip edge. Consider the concave polygon in the picture below by just clipping the lines it is divided in several separate polygons. Php polygon clipper using the sutherlandhodgman algorithm.
Polygon filling algorithm for each polygon for each edge, mark each scanline that the edge crosses by examining its y minand y max. Polygon clipping algorithm by sutherland and hodgeman c program. Sutherland and hodgmans polygonclipping algorithm uses a divideandconquer strategy. Each of the clipping planes are applied in succession to every triangle.
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