[vtkusers] Create polyData from 4 points

[Francesco Ferro]

Hi David,

Thank's for the answer! vtkAreaPicker is exactly the class I was looking 
for (using the frustum etc..) !! I tried to use it and it works very well
(I'm drawing 4 points around my 3d object, I call AreaPick and it 
returns me the prop3D of the actor where the frustum has intersected..).
Unfortunately this class can only return the "whole"" actor (and not the 
group of cell intersecting with the frustum). Usefull for me if I want 
only get Which cell is intersecting with the frustum...
for example if I select only half of my 3D object...and the delect all 
the cells in the frustum area...

So I will have a look to how AreaPicker class compute the intersections 
unless there is a class already doing that ?

Thank's again,



David E DeMarle wrote:
> Look at vtkAreaPicker::AreaPick() and ::DefineFrustum(). That uses the
> renderer to get 8 world space coordinates out of the four screen space
> coordinates. After that you need to create a vtkPolyData, makes those
> 8 points it's Points, and then make up one or more Cells that refer to
> those points.
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 28 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-371-3971 x109
>
>
>
> On Thu, Dec 3, 2009 at 12:34 PM, Francesco Ferro <le_maitre at bluewin.ch> wrote:
>   
>> Hi all,
>>
>> I would like to know if is it possible to create a polydata from 4 points ?
>> here an example of what I'm trying to do.
>>
>> 1. I have a windows where I can display 3D object and where I can draw with
>> the mouse on a 2 overlay (using Actor2D and polyMapper2D...)
>>
>> 2. I click on my windows 4 times that will create 4 points on my windows
>> (imagine I click the 4 edges of a square for example....)
>>
>> 3. I'd like then  draw lines between there 4 pointes (so it will display
>> like a 2d square...)
>>
>> 2. And then I'd like from these 4 points create a 3D object. with the X and
>> Y dimension I clicked and an "infinite" or very longue dimension in Z.
>>
>> Is there any easy way or Intelligent way to do that ? Storing the points in
>> a particular data or array ?
>>
>> Thank's in advance
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