[vtkusers] polygon fill / PointInPolygon

[chensiqi]

A further question:
 
If all my points on coplanar, the normal direction that returns from ComputeNomal will be either [0,0,1] or [0,0,-1], which makes sense in 3D view.
Rays shooting along this normal direction will never intersect with the edges of the polygon. I guess this is the reason why the whole region inside the bounding box is decided as "inside" ( 0 is an even number ). 
 
I did another experiment by choosing normal direction as [0.707, 0.707, 0]. The result is better, at least not the whole region in the bounds are given as "inside". But there many isolated points are still given wrong decisions due to numerical problem, I think.
 
What should I do under this coplanarity conditon?
 
Thanks
Siqi> Date: Tue, 16 Dec 2008 04:11:13 -0500> From: karthik.krishnan at kitware.com> To: pidanchen at hotmail.com> CC: vtkusers at vtk.org> Subject: Re: [vtkusers] polygon fill / PointInPolygon> > chensiqi wrote:> >> > Hi, VTKers> >> > I wonder if there is any Polygon fill algorithm implemented in> > VTKPolygon class?> >> > If not, maybe Loop through all the points using PointInPolygon is the> > only way I can think of.> Yes, at present the only way in VTK.> >> > Is that " n " in the parameter list of PointInpolygon the normal> > direction? How to estimate it?> Yes it is.> vtkPolygon::ComputeNormal should do the job for you.> > The method works by firing rays and checking the number of times a ray> drawn through the line intersects the polygon. Even times implies> outside, odd times => inside. The normal is needed to get the direction> the rays are fired in (they are perpendicular to the normal). The class> could have computed the normal for you, but it is left to the user for> efficiency, since its likely that you will call the methods several> times and wouldn't want to recompute the polygon normal each time.> > > int vtkPolygon::*PointInPolygon* (double x[3], int numPts, double> > *pts, double bounds[6], double *n)> >> > Thanks for your help.> >> > Siqi> >> >> >> > ------------------------------------------------------------------------> > 更多热辣资讯尽在新版MSN首页！ 立刻访问！ <http://cn.msn.com/>> > ------------------------------------------------------------------------> >> > _______________________________________________> > This is the private VTK discussion list.> > Please keep messages on-topic. Check the FAQ at: http://www.vtk.org/Wiki/VTK_FAQ> > Follow this link to subscribe/unsubscribe:> > http://www.vtk.org/mailman/listinfo/vtkusers> > > > -- > Karthik Krishnan> R & D Engineer,> Kitware Inc,> Ph: 518 371 3971 x119> Fax: 518 371 3971> 
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