Solution manual for computer graphics with open gl, 4e, donald d. A powerful but somewhat more complex clipping algorithm developed by weiler and atherton. There are several wellknown polygon clipping algorithms, each having its strengths and weaknesses. We will use the following algorithms for polygon clipping sutherlandhodgeman polygon clipping algorithm. Another approach to polygon clipping no extra clipping outside window works for arbitrary shapes avoids degenerate polygons outline of weiler algorithm.
Algorithms weiler atherton implementation 2d polygon. The clip boundary determines a visible and invisible region. The oldest one from 1974 is called the sutherlandhodgman algorithm. Weiler atherton polygon clipping search and download weiler atherton polygon clipping open source project source codes from. The weileratherton polygon cutting calculation clasps a subject polygon to a clasp polygon giving at least one yield polygons that lie completely inside the clasp polygon. When i was considering rolling my own, i found the weiler atherton.
An extension of weileratherton algorithm to cope with the. Polygon clipping sutherlandhodgmanpolygon clipping algorithm and weiler atherton polygon clipping algorithm. The weiler atherton is a polygon clipping algorithm especially for concave polygons clipping and overcomes the downside of sutherland hodgeman. Feb 25, 2018 the weiler atherton algorithm of polygons clipping has been cited in a lot of tutorials. Device an algorithm for weiler atherton polygon clipping where the clipping window can be any specified polygon. Search weiler atherton polygon clipping, 300 results found vtk polygon boolean operations on source code, vtk polygon boolean operations on the source and treatment effect is great, but more than 100,000 of the triangular patch is slowervtk polygon al boolean operations source code, the operation result is great, but for more than 100,000. It is used in the areas like computer graphics, games development and others where clipping of polygon is. The algorithm of it is been always a hot spot in computer graphics area. The weiler algorithm 1977 is even more complicated, but it is the one youll need if you want to clip a polygon against a nonrectangular window. Contribute to yinyanghuopengl development by creating an account on github. Replace crossing points with vertices form linked lists of edges change links at vertices enumerate polygon patches weiler atherton polygon clipping. Explain weiler atherton polygon clipping algorithm in detail ques10. The algorithm can handle arbitrary closed polygons, specifically where the clip and subject polygons may selfintersect. First make a list of all intersection points namely i 1, i 2, i 3.
However, it can be used in 3d through visible surface determination and with improved. In other words, just make getclippedpolygon a standalone function. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygon arearegion it is generally applicable only in 2d. The algorithm terminates when the entire border of the original subject polygon has been traced exactly once. Input is in the form of vertices of the polygon in clockwise order. We will remove or clip the part that is outside the window. Weiler atherton polygon clippingin this algorithm,the vertex processing. Device an algorithm for weiler atherton polygon clipping, where the clipping window.
Download weiler atherton polygon clipping algorithm source. Line clipping and polygon clipping is one of the most fundamental and common graphics clipping operation. The weiler atherton clipping algorithm is a general purpose 2d clipping algorithm. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygon arearegion. An arbitrary polygon clipping algorithm masters thesis. In the left side polygon clipping, we only remove the left part of the polygon, which is outside the window. Computer graphics sutherlandhodgeman polygon clipping. Sutherland hodgman polygon clipping university of helsinki.
Explain weileratherton polygon clipping algorithm and state. Weiler atherton polygon clipping free open source codes. It is performed by processing the boundary of polygon against each window corner or edge. Unlike sutherland hodgman polygon clipping algorithm, this algorithm is able to clip concave polygons without leaving any residue behind. The vertexprocessing procedures for window boundaries are modified so that concave polygon is displayed. The task is to clip polygon edges using the sutherlandhodgman algorithm. As the algorithm goes around the edges of the window, clipping the polygon, it encounters four types of edges. Algorithms weiler atherton implementation 2d polygon clipping the short version. Weileratherton polygon the weileratherton algorithm clipper. And in all the tutorials above in the best case, just common flourcharts may be found. Please, help me to make the implementation more efficient and. All four edge types are illustrated by the polygon in the following figure. Consider each edge e of clipping area and do following. Modelling complex shapes parametric polynomial curves weileratherton polygon clipper.
I found the weiler atherton algorithm to have the most potential for general polygon cutting. Clipingas shown in upper figure by means of selection of the original image polygon, we are able to cut the polygon by taking plane of the convex points. In geometry a polygon is a flat shape consisting of straightlines that are joined to form a circuit. The weiler atherton 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. Sutherlandhodgman polygon clipping you are encouraged to solve this task according to the task description, using any language you may know. Device an algorithm for weileratherton polygon clipping, where the clipping window can be any specified polygon. Modification of weileratherton algorithm to address loose. How to roll your own, for the hopelessly masochistic. We present such an efficient algorithm for clipping arbitrary 2d polygons. Weiler atherton polygon clipping algorithm avi clipping dxf algorithm edge clipping midi clipping polygon maker union polygon using aes algorithm code 120 of 60 pages. Union 18 v1, v2, v3, p0, v8, v4, p3, v0, v6, p1, p2 19 weiler atherton algorithm. Aug, 2018 weiler atherton polygon clipping algorithm problem 1 emaster.
Triangularization weiler atherton polygon clipper lclips a subject polygon to a clip polygon lboth polygons can be of any shape lresult. Derive the expression for t with respect to ith edge and pq line to be clipped in the. An extension of weileratherton algorithm to cope with the selfintersecting polygon abstract. Polygon clipping is one of those humble tasks computers do all the time. For example, we can find the intersecting points separately and then find for. Hello,here i am explaining the algorithm for polygon clipping. Implementation of weileratherton polygon clipping algorithm in rust. To evaluate this algorithm first we have to realize the problem in weileratherton algorithm. A superior methodology is to utilize a more broad section calculation, for example, the weileratherton polygon scissors.
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. Its a basic operation in creating graphic output of all kinds. A polygon can also be clipped by specifying the clipping window. 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. Polygon clipping is an especially important and frequent operation in high resolution graphics applications. The weiler atherton is a polygon clipping algorithm.
When the clipped polygons have two or more separate sections, then it is the concave polygon handled by this algorithm. Replace crossing points with vertices form linked lists of edges change links at vertices enumerate polygon patches weileratherton polygon clipping. The output of each case is input for the next case. Apr 18, 2017 14 weiler atherton polygon clipping this algorithm was developed clip a fill area that is either a convex polygon or a concave polygon. University academy formerlyip university cseit 76,626 views. Weiler atherton polygon clipping algorithm problem 1. Polygon clipping is a process in which we only consider the part which is inside the view pane or window. Solution manual complete download for computer graphics. Sutherlandhodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the. Computer graphics clipping sutherlandhodgman algorithm area clipping or polygon clipping weileratherton polygon clipping. Polygon clipping algorithm divide and conquer idea.
In my opinion it would make more sense to have a standalone function that takes a clipping polygon and a polygon to draw and returns the clipped collection of polygons. 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. Explain weileratherton polygon clipping algorithm and state its. Dda line drawing algorithm example in bangla duration.
It is used in areas like computer graphics and games development where clipping of polygons is needed. It is used in the areas like computer graphics, games development and others where clipping of polygon is needed. Weiler atherton polygon clipping algorithm is an algorithm made to allow clipping of even concave algorithms to be possible. Once you actually have a polygon clipping library, you just need to subtract polygon b from polygon a to get your first piece of output, and intersect polygons a and b to get your second piece of output. Difference between sutherland hodgman and weiler atherton. The basic idea of this algorithm is that instead of proceeding around the polygon edges as vertices are processed, we will follow the window boundaries.
Using this program clip the polygon against the rectangular window. Weiler atherton polygon clipping algorithm geeksforgeeks. A powerful but somewhat more complex clipping algorithm developed by weiler and atherton meets this requirement. The idea seemed fine and simple but as for coding implementation, it is not so easy. Computer graphics weileratherton polygon clipping javatpoint. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygonarearegion. Weiler atherton polygon clipping algorithm problem 1 emaster. In this paper a new algorithm has been proposed which can fix the problem of weiler atherton algorithm.
While most clipping algorithms are optimized for a rectangular clipping region, the wieler atherton algorithm can use simple polygons for both the subject of the clipping as well as the actual clipping region itself. 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. Sutherlandhodgman can also be extended into 3d space by clipping the polygon paths based on the boundaries of planes defined by the viewing space. The weiler atherton algorithm of polygons clipping in 2d may be briefly described as follows. The weileratherton clipping algorithm is a general purpose 2d clipping algorithm. Solutions for clipping polygons with holes were developed later weiler and atherton 1977, vatti 1992wang et al. Program to implement sutherlandhodgeman polygon clipping. The problem of weiler atherton algorithm lies in clipping selfintersecting polygon.
An extension of weileratherton algorithm to cope with the 1. The basics of weiler atherton polygon clipping algorithm are start from the first edge which is going inside the clipping area. Mar 11, 2018 the weiler atherton algorithm of polygons clipping in 2d may be briefly described as follows. Explain weiler atherton polygon clipping algorithm in detail. The algoirthm is simple and faster that vattis 1992 algorithm, which was designed for. First the polygon is clipped against the left edge of the polygon window to get new vertices of 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. Often, it is possible to feed a weird polygon to an algorithm. Pseudocode of sutherland and hodgmans polygonclipping algorithm. Explain weileratherton polygon clipping algorithm and. For each edge type, zero, one, or two vertices are added to the output list of vertices that define the clipped polygon. Liang and barsky present a pascal version of their algorithm and include an example for which the execution time using their algorithm is shown to be half of the execution time of the standard sutherlandhodgman reentrant polygon clipping algorithm.
When an edge of a candidatesubject polygon enters the clipping area, save the intersection point. Polygon clipping, polygon winding direction, polygon area, polygon centroid, centroid of multiple polygons, line intersection, pointline distance, segment intersection, polygon point containment, polygon triangulation, polygon voronoi diagram, polygon offset, polygon outline, polygon buffer, polygon union, polygon substraction. The clipping algorithms studied require a convex polygon in context of many applications. A convex polygon and a convex clipping area are given. In this algorithm, all the vertices of the polygon are clipped against each edge of the clipping window. Intersection start at intersection point if connected to an inside vertex, go there else step to an intersection point. The polygon clipping algorithm deals with four different clipping cases.