[vtkusers] vtkSmoothPolyDataFilter + unstructuredGrid

[Bill Lorensen]

If you shrink the dataset, you will generate extra points and smooth
the faces of each tetra. I do not think this is what you want.

If you try what David and I suggested, only the external vertices will
be smoothed.

On Fri, Dec 11, 2009 at 11:04 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
>> >
>> >
>
>