Now, make two lists, one for the clipping polygon, and the other for the clipped polygon. Computer graphics sutherlandhodgeman polygon clipping with computer graphics tutorial, line generation algorithm, 2d transformation, 3d computer. The task is to clip polygon edges using the sutherlandhodgman algorithm. There are several wellknown polygon clipping algorithms, each having its strengths and weaknesses. Computer graphics assignment help, sutherland hodgman algorithm, sutherlandhodgman algorithm any polygon of any type of arbitrary shape can be explained with the assist of some set of vertices connected with it. A polygon can be clipped by processing its boundary as a whole against each window edge. Polygon clipping sutherland hodgman algorithm a polygon can also be clipped by specifying the clipping window. Sutherland hodgman clipping algorithm, by wojciech mula. Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind. Using this program clip the polygon against the rectangular window. For each of the four sides of the clipping rectangle, consider the line l through the two points which define that side. This algorithm defines the polygon to be clipped as a subject polygon and the clipping region is the clip polygon. The output of a polygon clipper should be a sequence of vertices that define the clipped polygon boundaries. Program to implement sutherlandhodgeman polygon clipping.
The algorithm you present is not the sutherlandhodgmanalgorithm for clipping against an arbitrary polygon, but the cohensutherlandalgorithm for clipping against a rectangular viewport. The sutherland hodgman algorithm is a wellknown algorithm for clipping a polygon against a rectangle. The output of each case is input for the next case. Next, one side of the clip polygon is extended infinitely in both directions, and the path of the subject polygon is traversed. Sutherlandhodgeman polygon clipping programs and notes. Sutherlandhodgeman polygon clipping this program is for implementing sutherlandhodgeman polygon clipping. Application of sutherland hodgman polygon clipping. Vertex 3, which is inside, 1 and vertex 3 are saved. Classify those intersection points as entering or exiting. Cohen sutherland algorithm is a line clipping algorithm that cuts lines to portions which are within a rectangular area. Sutherlandhodgman polygonclipping algorithm right clip boundary bottom clip boundary left clip boundary top clip boundary idea. It accepts an ordered sequence of verices v1, v2, v3. Clip a polygon by successively clipping against each infinite clip edge after each clipping a new set of vertices is produced. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window.
Sutherland hodgman polygon clipping algorithm with numerical. Polygon clipping algorithm by sutherland and hodgeman c program. It does have some limitations, which well explore later. Sutherland hodgman polygon clipping algorithm with. Sutherlandhodgeman polygon clipping ecomputernotes. 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 sutherlandhodgman algorithm is an algorithm used for clipping polygons. That article explains the algorithm and it also explains the code.
Weiler atherton polygon clipping algorithm geeksforgeeks. Php polygon clipper using the sutherlandhodgman algorithm. This is a part of mumbai university mca colleges computer graphics cg mca sem 2. 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. Clipping polygons the sutherlandhodgman algorithm clipping polygons would seem to be quite complex. Sutherlandhodgman polygon clipping you are encouraged to solve this task according to the task description, using any language you may know. Consider the concave polygon in the picture below by just clipping the lines it is divided in several separate polygons. Jan 30, 2020 sutherland hodgeman polygon clipping algorithm.
Apr 18, 2017 11 sutherlandhodgman polygon clipping example we illustrate this algorithm by processing the area in figure against the left window boundary. The sutherland hodgman algorithm is used for clipping polygons. 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. Vertices from the input list are inserted into an output list if they lie on the visible side of the. A single polygon can actually be split into multiple polygons can you draw an example. First make a list of all intersection points namely i 1, i 2, i 3. Computer graphics sutherlandhodgeman polygon clipping. Aug 03, 2018 sutherland hodgeman polygon clipping method and example. Print the sequence of points that define the resulting clipped polygon.
Polygon clipping algorithm by sutherland and hodge. The oldest one from 1974 is called the sutherlandhodgman algorithm. Apr 06, 2020 polygon clipping clips the edges of polygon based on clipping window. Understanding sutherlandhodgman clipping for physics engines. While we try to clip the polygon under consideration along with any rectangular window, then we o. Explain sutherland hodgeman algorithm for polygon clipping. To accomplish this task, it is not enough to clip the lines one by one with e. Polygon clipping clips the edges of polygon based on clipping window. Clip polygon pto clipping edge foreachedge in polygon p. Algorithm has to calculate more number of intersection points over window boundary.
Sutherlandhodgeman clipping the sutherlandhodgeman triangle clipping algorithm uses a divideandconquer strategy. A powerful but somewhat more complex clipping algorithm developed by weiler and atherton meets this requirement. This image from wikimedia commons demonstrates this quite well. In vertexarray is the array of input polygon vertices. May 20, 2018 polygon clipping sutherland hodgman algorithm a polygon can also be clipped by specifying the clipping window. The sutherland hodgeman polygon clipping algorithm.
Sutherland hodgeman polygon clipping algorithm is used for polygon clipping. We can correctly clip a polygon by processing the polygon boundary as whole each window edge. The oldest one from 1974 is called the sutherland hodgman algorithm. The code snippet seems to be taken directly from the corresponding wikipedia article. Each of the clipping planes are applied in succession to every triangle.
The algorithm describes both the subject and the clip polygon by a. Sutherland hodgeman algorithm is an important algorithm in polygon clipping. Let r be the rectangular window whose lower lefthand corner is at l 3, 1 and upper righthand corner is at r 2, 6. Sutherland hodgeman polygon clipping method and example. May 19, 2011 sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Sutherlandhodgman polygon clipping complexity of this algorithm will increase if number of edges of polygon increase. Polygon clipping sutherlandhodgman algorithm geeksforgeeks. Mar 20, 2015 polygon clipping algorithm by sutherland and hodge. Its a basic operation in creating graphic output of all kinds. Sutherlandhodgman polygon clipping algorithm thanks again for watching. Explain weileratherton polygon clipping algorithm and. Sutherland hodgman polygon clipping algorithm author. A convex polygon and a convex clipping area are given.
First the polygon is clipped against the left edge of the polygon window to get new vertices of the. To generate first and follow for given grammar c programsystem programming and compiler constructionheres a c program to generate first and follow for a give grammar program. 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. In this algorithm, all the vertices of the polygon are. In the left side polygon clipping, we only remove the left part. The sutherland hodgeman polygon clipping algorithm slideshare. The sutherland hodgeman polygon clipping algorithm is relatively straightforward and is easily implemented in c.
The sutherlandhodgman algorithm clips a polygon against all edges of the clipping region in turn. Disadvantages of sutherland hodgman polygon clipping. 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. If we clip its edges they will disappear, and the polygon will vanish. Sutherland and hodgmans polygonclipping algorithm uses a divideandconquer strategy. The algorithm steps from vertex to vertex, adding 0, 1, or 2 vertices to the output list at each step. The polygon clipping algorithm deals with four different clipping cases. The sutherlandhodgman clipping algorithm finds the polygon that is the intersection between an arbitrary polygon the subject. The sutherlandhodgeman polygon clipping algorithm is relatively straightforward and is easily implemented in c. Sutherlandhodgeman polygon clipping algorithm c program. Algorithm for partitioning a general closed polygon. The algorithm steps from vertex to vertex, adding 0.
Clip polygon pto clipping edge foreachedge in polygon p check clipping cases there are 4 case 1. The following example illustrate a simple case of polygon clipping. Php polygon clipping using the sutherlandhodgman algorithm clip. Polygon clipping is one of those humble tasks computers do all the time. The idea is to clip each line segment of the input polygon against one clipping plane at a time. The sutherlandhodgmanalgorithm is a wellknown algorithm for clipping a polygon against a rectangle. The region code for point x, y is set according to the scheme. A polygon can also be clipped by specifying the clipping window. In this video, i have explained the a numerical on the sutherland hodgman polygon clipping algorithm. Php polygon clipping using the sutherlandhodgman algorithm. The task is to clip polygon edges using the sutherland hodgman algorithm. 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. It eliminates the lines from a given set of lines and rectangle area of interest view port which belongs outside the area of interest and clip those lines which are partially inside the area of interest.
Explain weileratherton polygon clipping algorithm and state. Example of cohensutherland line clipping algorithm. May 06, 2019 sutherland hodgman polygon clipping algorithm sutherland algorithm hello friends. The sutherland hodgman algorithm performs a clipping of a polygon against each window edge in turn. Consider each edge e of clipping area and do following.
It is performed by processing the boundary of polygon against each window corner or edge. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. This is achieved by processing all polygon vertices against each clip rectangle boundary in turn. The algorithm takes an input polygon and some clipping planes, and outputs a new polygon. It works by extending each line of the convex clip polygon in turn and selecting. Sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Sutherland hodgman polygon clipping algorithm pracspedia. Could any one can help me about the example of source code for the sutherlandhodgman method to polygon clipping. Algorithm for each boundary b in l, r, t, b if p 1 outside and p 2 inside output intersection output p 2 if p 1 inside and p 2 inside output p 2 if p 1 inside and p 2 outside output intersection if p 1 outside and p 2 outside do nothing. Sutherland hodgman polygon clipping algorithm sutherland algorithm hello friends. The algorithm describes both the subject and the clip polygon by a circular list of vertices. I wrote a php implementation of the polygon clipping algorithm by sutherlandhodgman. Sutherlandhodgman polygon clipping algorithm youtube.
Input is in the form of vertices of the polygon in clockwise order. 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. 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. This is algorithm is used to clip the polygon which lies inside the window boundary. It solves a series of simple and identical problems that, when combined, solve the overall problem.