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. 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. Clip polygon pto clipping edge foreachedge in polygon p. Consider each edge e of clipping area and do following. Texturing, clipping reading texture mapping example texture map. Polygon clipping sutherland hodgman algorithm a polygon can also be clipped by specifying the clipping window. Sutherland hodgman polygon clipper by hamed sheidaian from. Sutherlandhodgeman polygon clipping programs and notes for. The advantages of sutherland hodgman algorithm are. Pseudo code given a list of edges in a clip polygon, and a list of vertices in a subject polygon, the following procedure clips the subject polygon against the clip polygon. In the first case, p1 is in front of the plane and p2 is on the back. This code clip a polygon with sutherland hodgman algorithm. Polygon clipping sutherlandhodgman algorithm point clipping algorithm in computer graphics.
The sutherland hodgman algorithm performs a clipping of a polygon against each window edge in turn. Video explains with help of an example the working of the algorithm. This is a part of mumbai university mca colleges computer graphics cg mca sem 2. Sutherlandhodgeman polygon clipping algorithm c program. Multiplepolygons may result from clipping a singlepolygon. Pseudo code given a list of edges in a clip polygon, and a list of vertices in a subject polygon, the following. Php polygon clipping using the sutherland hodgman algorithm clip. The algorithm steps from vertex to vertex, adding 0. Sutherlandhodgman polygon clipping you are encouraged to solve this task according to the task description, using any language you may know. In polygon clipping, we use an algorithm that generates one or more closed areas that are then scan converted for the appropriate area fill. Write advantages of sutherlandhodgman polygon clipping.
Sutherlandhodgeman polygon clipping ecomputernotes. It works by extending each line of the convex clip polygon. Sutherlandhodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the viewing space. It clips a polygon against all edges of the clipping region. Two possible cases in bresenhams line drawing algorithm. Explain sutherland hodgeman algorithm for polygon clipping. Cases of the sutherland hodgman polygon clipping algorithm. If the polygon is not also convex, there may be some dangling. For this example, i think the size of window is 800 600, viewport region is also 800 600, and clipping region could be 10043100. What is sutherlandhodgman polygon clipping algorithm in. Polygon clipping sutherlandhodgman algorithm geeksforgeeks. 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.
The sutherlandhodgmanalgorithm is a wellknown algorithm for clipping a polygon against a rectangle. Sutherland and hodgmans polygonclipping algorithm uses a. The oldest one from 1974 is called the sutherlandhodgman algorithm. In vertexarray is the array of input polygon vertices. Sutherland hodgeman polygon clipping this program is for implementing sutherland hodgeman polygon clipping. Sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. It is performed by processing the boundary of polygon against each window corner or edge. Disadvantages of sutherland hodgman polygon clipping. Polygon clipping algorithm by sutherland and hodgeman c program. Program to show the implementation of sutherland hodgeman polygon clipping. The laingbarsky algorithm 1983 is a good deal more complicated, but in certain cases fewer intersections need to be calculated than for sutherlandhodgman. Given geometry in the world coordinate system, how do we get it. Polygon clipping algorithm by sutherland and hodgeman c.
Could any one can help me about the example of source code for the sutherlandhodgman method to polygon clipping. May 19, 2011 sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Sutherland and hodgman s polygon clipping algorithm uses a divideandconquer strategy. Using this program clip the polygon against the rectangular window. 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 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. The simple problem is to clip a polygon against a single infinite clip edge. The task is to clip polygon edges using the sutherland hodgman algorithm. Program of sutherland hodgemann algorithm for polygon clipping. Sutherland and hodgmans polygonclipping algorithm uses a divideandconquer strategy. Program to implement sutherlandhodgeman polygon clipping.
That article explains the algorithm and it also explains the code. Due to the size or complexity of this submission, the author has submitted it as a. Apr 05, 20 sutherland hodgman algorithm each edge of the polygon must be testedagainst each edge of the clip rectangle. In geometry a polygon is a flat shape consisting of straightlines that are joined to form a circuit. The algorithm you present is not the sutherlandhodgmanalgorithm for clipping against an arbitrary polygon, but the cohensutherlandalgorithm for clipping against a rectangular viewport. 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 solves a series of simple and identical problems that, when combined, solve the overall problem. Php polygon clipper using the sutherlandhodgman algorithm. Let me explain the algorithm of sutherland hodgman using the above situation. We will be discussing cyrusbeck algorithm in next set. Polygon clipping algorithm by sutherland and hodge. In the second instance, no points are saved since they both lie on the back of the plane. Program to illustrate the implementation of 3d rotation transformation along.
Implement polygon clipping using sutherlandhodgeman algorithm. May 30, 2014 a simple video that explains the working of sutherland hodgman polygon clipping algorithm in detail. It steps from vertex to vertex and adds 0, 1, or 2 vertices at each step to the output list. Sutherlandhogson polygon clipping javascript github. A polygon can be clipped by processing its boundary as a whole against each window edge. The code snippet seems to be taken directly from the corresponding wikipedia article. May 07, 2017 in this video we will learn sutherland hodgeman polygon clipping algorithm. This program is a simple opengl program, and draw a glass model of the red and blue color, and staggered some distance display, water cup autorotate feature, after configuring opengl environment vs2010 be able to compile the source program is running, and source code related to the opengl function. Jun 19, 2016 2c using the previously generated polygon, repeat the sutherland hodgman algorithm to the right reference plane. Sutherland hodgman polygon clipping university of helsinki. This is achieved by processing all polygon vertices against each clip rectangle boundary in turn. There are several wellknown polygon clipping algorithms, each. Sutherland hodgeman polygon clipping algorithm is used for polygon clipping. Use this algorithm to draw a line with endpoints 2, 3.
The cohensutherland algorithm can be used only on a rectangular clip window. This algorithm does not work if the clip window is not convex. Consider the concave polygon in the picture below by just clipping the lines it is divided in several separate polygons. For other convex polygon clipping windows, cyrusbeck algorithm is used. It accepts an ordered sequence of verices v1, v2, v3.
Php polygon clipping using the sutherlandhodgman algorithm. Solved clipping region in animation with opengl example. Application of sutherland hodgman polygon clipping, computer. The sutherlandhodgman algorithm clips a polygon against all edges of the clipping region in turn. Sutherlandhodgman algorithm each edge of the polygon must be testedagainst each edge of the clip rectangle. Program to show the implementation of liangbarsky line clipping algorithm. The task is to clip polygon edges using the sutherlandhodgman algorithm. Clip polygon pto clipping edge foreachedge in polygon p check clipping cases there are 4 case 1.
There is a program about animation with opengl in chapter 2. Im not quite sure whether you understood the sutherlandhodgman algorithm correctly or at least i didnt get your example. 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. Sutherland hodgman polygon clipping algorithm pracspedia. Max is a declared constant procedure sutherlandhodgmanpolygoclip invertexarray. Clipping polygons the sutherlandhodgman algorithm clipping polygons would seem to be quite complex. Mar 20, 2015 polygon clipping algorithm by sutherland and hodge. 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. Input is in the form of vertices of the polygon in clockwise order. The sutherland hodgman algorithm is used for clipping polygons. Therefore, it may be somewhat faster when many polygon lines intersect with the clipping boundaries.
Sutherlandhodgeman polygon clipping this program is for implementing sutherlandhodgeman polygon clipping. Php polygon clipping using the sutherlandhodgman algorithm clip. Subramanian usage click on the canvas to seed the points of the polygon press d to draw the seeded polygon drag the mouse cursor to draw the required clip rectangle press c to clip the required polygon section. This code clip a polygon with sutherlandhodgman algorithm. Let me explain the algorithm of sutherlandhodgman using the above situation.
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. We need an organized way to dealwith all these cases. Visualizing the sutherland hodgman algorithm harold serrano. Computer graphics sutherlandhodgeman polygon clipping. The algorithm proceeds in stages by passing each clipped polygon to the next edge of the windows and clipping. Thus, an intersection point is calculated and saved. I wrote a php implementation of the polygon clipping algorithm by sutherlandhodgman. The output of a polygon clipper should be a sequence of vertices that define the clipped polygon boundaries.