[Paraview] new Source plugin: no show!

[Burlen Loring]

Hi Bertwim,

I should have explained the cells better. The cells are descriptions of 
how points are combined into geometric primitives that can be rendered 
by OpenGL (or converted into those understood by OpenGL). Here is an 
excerpt <http://www.vtk.org/VTK/img/file-formats.pdf> of the User Guide 
describing VTK's cells, see p9-10.

Burlen

On 10/5/2014 8:17 AM, B.W.H. van Beest wrote:
> Hi Burlen,
>
> Thanks for your reply. On the cell-info:  I now (finally) understood 
> what was there to be. After implementing the cells, I indeed got the 
> expected display. On the book: what keeps me from buying is that it 
> seems outdated (because it refers to version 3).
> The texture coordinates I had found on Google indeed. What I needed 
> was how to apply it in Paraview/VTK. I will look into that again Maybe 
> it becomes clear now.
>
> Thanks
> Bertwim
>
>
> On 10/05/2014 05:05 AM, Burlen Loring wrote:
>> I assume in your request data you are generating a vtkPolyData 
>> dataset. At the end of request data call "dataset->Print(cerr);" . 
>> That's the one of the best debug method when you don't see what you 
>> think you should in PV while developing a new filter/source/reader 
>> what ever. The information tab in the GUI gives a subset of that, 
>> also useful.
>>
>> texture coordinates are usually for applying an image to the surface. 
>> google it and you'll find volumes of info. In pv they are optional.
>>
>> the cell array I'm afraid is not. when generating poly or 
>> unstructured data. If you have no cells what do you expect to see?
>>
>> normals are per point.
>>
>> some of your questions suggest that the book VTK user guide 
>> <http://www.kitware.com/products/books/vtkguide.html> would be a good 
>> investment for you.
>>
>> Hope I didn't miss anything. ;-)
>>
>> On 10/4/2014 8:30 AM, B.W.H. van Beest wrote:
>>> Hello,
>>>
>>> I need to write a new Source, representing a 'TriPrism",
>>> i.e. a prism where the top and bottom planes are triangles. So far, I
>>> failed.
>>>
>>> Being unable to find appropriate documentation, I used the source code
>>> of vtkCubeSource as an example, thinking it would be an easy change.
>>> Wrong! The prism doesn't show on the screen. The
>>> properties panel behaves as expected (and ok, as far I can see).
>>>
>>> The member function 'RequestData' seems to be the important method.
>>> But the code of the example (as well as other source examples) is on
>>> closer inspection not clear to me at all.
>>>
>>> The following is happening in the vtkCubeSource:
>>>
>>> a)   The point of the cube are generated.  This is straightforward and
>>> easily
>>>          translates to the triprism.
>>>         The new points are updated via a call "output->setPoints(
>>> newPoints );"
>>>
>>> b)   The normals (to the side planes of the cube) are being calculated.
>>>         The new normals are updated via a call
>>>         "output->GetPointData()->SetNormals(newNormals);"
>>>          This is also straightforward for the triprism, but:
>>>
>>>         Q: although calculating the normals is straightforward,
>>>              in which order are they supposed to be given?
>>>
>>> c)     Also, texture coordinates (TCoords) are calculated.
>>>           Q: What are these?  Are these mandatory?
>>>
>>> d)     Also, a new vtkCellArray is being created. ('newPolys')
>>>            Q: Same question. No clue what I should do here.
>>>
>>> As usual, any clue of how to attack this is greatly appreciated.
>>>
>>> Bertwim
>>>
>>>
>>>
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