[vtkusers] vtkSmoothPolyDataFilter + unstructuredGrid

[David Gobbi]

By "vtkDataSurfaceFilter" you mean "vtkGeometryFilter", right?

And no, the interior hexahedrons are definitely not smoothed.  No way
no how.  And because of this, some of the inside points might end up
on the outside after smoothing, resulting in an invalid data set.

You need a step 5 which smooths the interior points, based on the
connectivity information.  Such a filter does not exist in VTK, it
would have to be written.

   David


On Fri, Dec 11, 2009 at 9:04 AM, Bill Chivas <noo134 at googlemail.com> wrote:
> Thank you both.
> I'll try out your suggestions.
> By far, i tried the following pipeline:
> 1) UnstructuredGrid
> 2) vtkShrinkFilter (so i can see the hexahedrons)
> 3) vtkDataSetSurfaceFilter (!)
> 4) vtkSmoothPolyDataFilter
>
> I get what i want. I'm not really sure if ALL hexahedrons are smoothed (and
> not only the outer ones).
> What do you think?
>
> Thanks,
> Bill
>
>
>
> 2009/12/11 David Gobbi <david.gobbi at gmail.com>
>>
>> Hmm... if GeometryFilter keeps all the points, then it's possible that
>> you could generate a new vtkDataSet that combines the points from the
>> smoothed polydata with the cells of your grid.  Something like this:
>>
>> smoothFilter->Update();
>> gridProducer->Update();
>> vtkDataSet *newdata = vtkDataSet::New();
>> newdata->DeepCopy(gridProducer->GetOutput());
>> newdata->SetPoints(smoothFilter->GetOutput()->GetPoints());
>>
>> Note that code like this can crash if the assumptions aren't correct.
>> Also, only the outer layer of points will be smoothed, so the
>> resulting data object might contain invalid cells.  But still, this
>> should give you ideas about how to find a proper solution.
>>
>>    David
>>
>>
>> On Fri, Dec 11, 2009 at 8:40 AM, Bill Chivas <noo134 at googlemail.com>
>> wrote:
>> > vtkGeometryFilter works fine. I wonder if i could get back to
>> > unstructuredGrid and hexahedrons by using the points.
>> > I noticed that the number of points are the same in unstructuredGrid and
>> > vtkGeometryFilter (vtkPolyData).
>> > Could i "reproduce" the original hexahedron topology?
>> >
>> > Thanks,
>> > Bill
>> >
>> > 2009/12/11 David Gobbi <david.gobbi at gmail.com>
>> >>
>> >> On Fri, Dec 11, 2009 at 7:11 AM, Bill Chivas <noo134 at googlemail.com>
>> >> wrote:
>> >> > Hello all,
>> >> >
>> >> > I would like to use vtkSmoothPolyDataFilter  on an unstructuredGrid,
>> >> > but
>> >> > i
>> >> > read the particular filter applies only to vtkPolyData.
>> >> > My unstructuredGrid consists of hexahedrons.
>> >> > How could i use the filter?
>> >> > One idea i thought is to extract the surface iterately and apply to
>> >> > these
>> >> > surfaces, but i don't know if it's ok.
>> >>
>> >> I've seen some people create a "skin" polydata with vtkGeometryFilter,
>> >> apply the smoothing to the "skin" and then use a custom filter to
>> >> propagate the smoothing throughout the interior of their mesh.  The
>> >> vtkGeometryFilter is a basic anything-to-polydata filter, so it is
>> >> easy to use.  The final step of using the smoothed polydata to create
>> >> a smoothed mesh is nontrivial, though.
>> >>
>> >>    David
>> >
>> >
>
>