Sutherland hodgman polygon clipping algorithm example

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. 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. The laingbarsky algorithm 1983 is a good deal more complicated, but in certain cases fewer intersections need to be calculated than for sutherlandhodgman. Therefore, it may be somewhat faster when many polygon lines intersect with the clipping boundaries. Polygon clipping ppt polygon convex set free 30day. First make a list of all intersection points namely i 1, i 2, i 3. Video explains with help of an example the working of the algorithm. Sutherland hodgman polygon clipping university of helsinki. Write advantages of sutherlandhodgman polygon clipping. Input is in the form of vertices of the polygon in clockwise order. Sutherlandhogson polygon clipping javascript github. If both vertices are inside the clipping area save the second.

Polygon clipping algorithm by sutherland and hodge. The algorithm steps from vertex to vertex, adding 0. The task is to clip polygon edges using the sutherland hodgman algorithm. 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. The task is to clip polygon edges using the sutherlandhodgman 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. A single polygon can actually be split into multiple polygons can you draw an example. This is achieved by processing all polygon vertices against each clip rectangle boundary in turn. Clip a polygon by successively clipping against each infinite clip edge after each clipping a new set of vertices is produced.

Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind. 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. Disadvantages of sutherland hodgman polygon clipping. Polygon clipping sutherland hodgman algorithm a polygon can also be clipped by specifying the clipping window. The algorithm you present is not the sutherlandhodgmanalgorithm for clipping against an arbitrary polygon, but the cohensutherlandalgorithm for clipping against a rectangular viewport. 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 clipping sutherlandhodgman algorithm geeksforgeeks. Weiler atherton polygon clipping algorithm geeksforgeeks. Each of the clipping planes are applied in succession to every triangle. A convex polygon and a convex clipping area are given. When clipping a convex polygon to a convex view polygon, the conservative assertion is that each line of the clipping polygon can add one vertex to the convex polygon being clipped. It solves a series of simple and identical problems that, when combined, solve the overall problem. In this video, i have explained the a numerical on the sutherland hodgman polygon clipping algorithm. 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.

Clip polygon pto clipping edge foreachedge in polygon p. 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 by dinesh thakur category. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window. Clipping polygons the sutherlandhodgman algorithm clipping polygons would seem to be quite complex. Cohen sutherland algorithm is a line clipping algorithm that cuts lines to portions which are within a rectangular area. Sutherlandhodgeman polygon clipping programs and notes. The sutherlandhodgman clipping algorithm finds the polygon that is the intersection between an arbitrary polygon the subject. Derive the expression for t with respect to ith edge and pq line to be clipped in the. The sutherland hodgman clipping algorithm finds the polygon that is the intersection between an arbitrary polygon the subject polygon and a convex polygon the clip polygon.

Computer graphics sutherlandhodgeman polygon clipping. The sutherlandhodgeman triangle clipping algorithm uses a divideandconquer strategy. Sutherlandhodgeman polygon clipping this program is for implementing sutherlandhodgeman polygon clipping. The sutherland hodgman algorithm clips a polygon against all edges of the clipping region in turn. 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. Sutherlandhodgeman polygon clipping algorithm c program. Program to implement sutherlandhodgeman polygon clipping.

It accepts an ordered sequence of verices v1, v2, v3. Sutherland hodgman polygon clipping algorithm with. Imagine a square as a viewport, and rotate the square by 45 degrees as an example convex polygon. The first step is to identify the reference and the incident polygon. The sutherland hodgman algorithm performs a clipping of a polygon against each window edge in turn. Php polygon clipping using the sutherlandhodgman algorithm.

The following example illustrate a simple case of polygon clipping. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. The code snippet seems to be taken directly from the corresponding wikipedia article. What is sutherlandhodgman polygon clipping algorithm in. A polygon can be clipped by processing its boundary as a whole against each window edge. The sutherlandhodgman algorithm is an algorithm used for clipping polygons. What am i doing wrong with the sutherland hodgman algorithm.

Explain sutherland hodgeman algorithm for polygon clipping. Sutherland hodgeman polygon clipping the algorithm begins with an input list of all vertices in the subject polygon. Clipping polygons the sutherland hodgman algorithm clipping polygons would seem to be quite complex. Sutherland hodgman polygon clipping algorithm author. Consider each edge e of clipping area and do following.

Print the sequence of points that define the resulting clipped polygon. Vertices from the input list are inserted into an output list if they lie on the visible side of the. Sutherlandhodgman polygonclipping algorithm right clip boundary bottom clip boundary left clip boundary top clip boundary idea. Hodgman evans and sutherland computer corporation a new family of clipping algorithms is described. Input is in the form of vertices of the polygon in clockwise order examples. Since there is only one output vertex list, the last vertex in the list is always joined to the first vertex. That article explains the algorithm and it also explains the code. The sutherlandhodgmanalgorithm is a wellknown algorithm for clipping a polygon against a rectangle. Consider the concave polygon in the picture below by just clipping the lines it is divided in several separate polygons. Sutherlandhodgeman polygon clipping ecomputernotes. 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 4 rules explained in sutherlandhodgman algorithm for clipping polygons. In polygon clipping, we use an algorithm that generates one or more closed areas that are then scan converted for the appropriate area fill.

Sutherland hodgman polygon clipping algorithm problem 1. 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. Sutherland hodgeman polygon clipping algorithm is used for polygon clipping. The input polygons are always quads that consist of four points.

A simple video that explains the working of sutherlandhodgman polygon clipping algorithm in detail. It works by extending each line of the convex clip polygon in turn and selecting. Sutherland and hodgmans polygonclipping algorithm uses a divideandconquer strategy. It works by extending each line of the convex clip polygon. To accomplish this task, it is not enough to clip the lines one by one with e. Im struggling to find a good, working implementation of the sutherlandhodgman algorithm for clipping one polygon by the edges of another polygon. It is performed by processing the boundary of polygon against each window corner or edge. Php polygon clipping using the sutherlandhodgman algorithm clip. It clips a polygon against all edges of the clipping region. Sutherland hodgman polygon clipping algorithm pracspedia. Sutherland hodgman polygon clipping algorithm sutherland algorithm hello friends. Sutherlandhodgman polygon clipping algorithm youtube. Using this program clip the polygon against the rectangular window.

There is minimal storage requirements for this algorithm, and it is well suited for pipelining. It steps from vertex to vertex and adds 0, 1, or 2 vertices at each step to the output list. These algorithms are able to clip polygons against ir regular convex planefaced volumes in three dimensions. The sutherlandhodgman algorithm clips a polygon against all edges of the clipping region in turn. The output of a polygon clipper should be a sequence of vertices that define the clipped polygon boundaries. Polygon clipping algorithm by sutherland and hodgeman c.