[vtkusers] Example of PointInPolygon

[rakesh patil]

Hi

I am using points and not vertex points. Also the example given by David, is
instructing me the similar method to use.

In the above code i made a small change. Instead of.

newPoints->InsertNextPoint( points->GetPoint(id));

I wrote

double pt[3];
points->GetPoint(id, pt);
newPoints->InsertNextPoint(pt);

After this change i am getting strange result. The result in "newPoints" is
all the points that fall inside a region defined by bounds. i.e. a
rectangular region which is formed by the bounds.

This is really getting interesting and strange.. :-)

Thanks

Warm Regards
Rakesh Patil

On Wed, Sep 29, 2010 at 5:09 PM, Jothy <jothybasu at gmail.com> wrote:

> Are you using vertex points instead of points inside the polygon. I mean,
> in case of a sphere, are using surface points rather than points inside the
> sphere.
>
> I think there is some difficulty in accurately calculating whether a point
> is inside or outside a polygon, if you submit a point which lies on or very
> close to the surface due to round-off errors in the ray-tracing used.
>
>
> Jothy
>
>
> On Wed, Sep 29, 2010 at 12:23 PM, rakesh patil <prakeshofficial at gmail.com>wrote:
>
>> hi,
>>
>> Below is the sample code what i was trying.
>>
>> int num = polyPd->GetNumberOfPoints();
>> // polyPd is a polydata containing points that forms a polygon
>>
>> vtkPoints* points = this->del->GetOutput()->GetPoints();
>> // del is an instance of vtkDelaunay2d class. Out of this object is used
>> to display
>> // scattered points
>>
>> vtkPoints *newPoints = vtkPoints::New();
>> // To store selected points
>>
>> double bnds[6], n[3];
>>
>> // Get the bounds in 'bnds'
>> polyPd->GetPoints()->GetBounds(bnds);
>>
>> // To get normal direction in 'n'
>> vtkPolygon::ComputeNormal(num,
>>   static_cast<double
>> *>(polyPd->GetPoints()->GetData()->GetVoidPointer(0)), n);
>>
>> for( int id = 0; id < points->GetNumberOfPoints(); id++ )
>> {
>>   if( vtkPolygon::PointInPolygon( points->GetPoint(id), num,
>>       static_cast<double
>> *>(polyPd->GetPoints()->GetData()->GetVoidPointer(0)), n) == 1 )
>>        newPoints->InsertNextPoint(points->GetPoint(id));
>> }
>>
>> // code to create a mapper and actor with
>> // the help of newPoints
>>
>> I hope there is no difficulty in understanding the other part of code. I
>> got this logic from the mailing list when i searched for PoinInPolygon here
>>
>> http://public.kitware.com/pipermail/vtkusers/2010-April/107974.html
>>
>> Thanks
>>
>> Warm Regards
>> Rakesh Patil
>>
>>
>> On Wed, Sep 29, 2010 at 3:49 PM, Jothy <jothybasu at gmail.com> wrote:
>>
>>> Could you please post your code?
>>>
>>> Jothy
>>>
>>>  On Wed, Sep 29, 2010 at 11:09 AM, rakesh patil <
>>> prakeshofficial at gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> I have been trying to find whether a given point is within a polygon or
>>>> not. I have been doing this using,
>>>>
>>>> vtkPolygon::PointInPolygon()
>>>>
>>>> function. But out of 10 runs, in 1 run, i get only few points inside,
>>>> the polygon. Others just fails and shows 0 points selected.
>>>>
>>>> Can anyone come up with a small example, for this?
>>>>
>>>> Thanks
>>>>
>>>> Warm Regards
>>>> Rakesh Patil
>>>>
>>>> _______________________________________________
>>>> Powered by www.kitware.com
>>>>
>>>> Visit other Kitware open-source projects at
>>>> http://www.kitware.com/opensource/opensource.html
>>>>
>>>> Please keep messages on-topic and check the VTK FAQ at:
>>>> http://www.vtk.org/Wiki/VTK_FAQ
>>>>
>>>> Follow this link to subscribe/unsubscribe:
>>>> http://www.vtk.org/mailman/listinfo/vtkusers
>>>>
>>>>
>>>
>>>
>>> --
>>> PhD Student
>>> Dept. of Medical Physics
>>> Clatterbridge Centre for Oncology
>>> UK
>>>
>>>
>>
>
>
> --
> PhD Student
> Dept. of Medical Physics
> Clatterbridge Centre for Oncology
> UK
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20100929/0996db67/attachment.htm>