[vtkusers] vtkCutClosedSurface

[David Gobbi]

Hi Sebastien,

Yes, you can use vtkThreshold _after_ using vtkClipClosedSurface.  Use
SetScalarModeToLabels() on vtkClipLosedSurface, and make sure that you
threshold the cell scalars (not point scalars).  The cell scalars of
the cut faces will be set to 1 or higher.

 - David


On Mon, Oct 10, 2011 at 6:25 AM, sebastian ordas
<sebastian.ordas at gmail.com> wrote:
> Hello David,
>
> vtkClipClosedSurface does exactly what I need
>
> http://ScrnSht.com/jyutyz
> http://ScrnSht.com/kwanbu
>
> except that I need the yellow triangulation only ...
>
> What would you advice? adding to vtkClipClosedSurface the possibility of
> getting the "yellow cap" only or writing a vtkCutClosedSurface filter class
> for that single operation?
>
> btw, isn't it possible to pipeline vtkThreshold to vtkClipClosedSurface
> somehow?
>
> thank you,
> sebastian
>
> On 10/07/2011 03:20 PM, David Gobbi wrote:
>>
>> I can't remember the details of how to apply constraints with
>> vtkDelaunay2D, but it definitely can be done.
>>
>>  - David
>>
>>
>> On Fri, Oct 7, 2011 at 10:35 AM, sebastian ordas
>> <sebastian.ordas at gmail.com>  wrote:
>>>
>>> Hi David,
>>>
>>> sorry, my mistake
>>> I had a copy and paste typo in one of my actors:
>>> actor->SetScale(1.01,1.01,1.01);
>>>
>>> I tested vtkDelaunay2D. It looks pretty stable but I would like to avoid
>>> meshing the holes and outside the contour:
>>> http://ScrnSht.com/grcbwa
>>>
>>> For the former, I guess I need to use "SetSourceConnection" right?
>>> But how to avoid the latter?
>>>
>>> best regards,
>>> sebastian
>>>
>>>
>>> On 10/7/2011 12:00 PM, David Gobbi wrote:
>>>>
>>>> Hi Sebastian,
>>>>
>>>> The filter does not move any points in the mesh (it just adds/removes
>>>> points).  Check the transform matrices for your actors, from the
>>>> picture it looks more like a scale difference than a shift but it is
>>>> hard to tell.
>>>>
>>>>  - David
>>>>
>>>>
>>>> On Fri, Oct 7, 2011 at 7:42 AM, sebastian ordas
>>>> <sebastian.ordas at gmail.com>    wrote:
>>>>>
>>>>> Thank you David!
>>>>>
>>>>> btw, using vtkClipClosedSurface, I´m getting a small shift between the
>>>>> original mesh and the closed clipped surface
>>>>> http://ScrnSht.com/byxsiw
>>>>>
>>>>> Is that a visualization issue only?
>>>>>
>>>>> regards,
>>>>> sebastian
>>>>>
>>>>>
>>>>> On 10/7/2011 3:06 AM, David Gobbi wrote:
>>>>>>
>>>>>> On Thu, Oct 6, 2011 at 4:06 PM, sebastian ordas
>>>>>> <sebastian.ordas at gmail.com>      wrote:
>>>>>>>
>>>>>>> Dear VTK developers,
>>>>>>>
>>>>>>> Following the explanation in
>>>>>>> http://www.vtk.org/Wiki/VTK/Closed_Surface_Clipping
>>>>>>> I was wondering about the current development state of the
>>>>>>> vtkCutClosedSurface class or a similar one.
>>>>>>
>>>>>> It has not been written.  Eventually I might need it, and when I do,
>>>>>> I'll write it... but that could be in a few months, a few years, or
>>>>>> never.
>>>>>>
>>>>>>> I´m basically needing the meshing of a contour, possibly with holes,
>>>>>>> but
>>>>>>> always closed.
>>>>>>
>>>>>> You can use vtkDelaunay2D for that, but be warned that some inputs
>>>>>> will cause vtkDelaunay2D to segfault (it is rare, but it does happen
>>>>>> occasionally).
>>>>>>
>>>>>>> I found this interesting:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> http://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf
>>>>>>
>>>>>> That method is very similar to the one that vtkClipClosedSurface uses.
>>>>>> It is messy but it is robust.  The fastest triangulation methods are
>>>>>> randomized Delaunay methods, but they are very sensitive to roundoff
>>>>>> error, and as a result it is hard to write a robust Delaunay
>>>>>> algorithm.
>>>>>>
>>>>>>> Does anyone know a workaround (has to be fast, for a real time
>>>>>>> application)
>>>>>>> with existing VTK classes?
>>>>>>
>>>>>> For now, vtkDelaunay2D is the only class for doing triangulations with
>>>>>> holes.
>>>>>>
>>>>>>  - David
>>>
>
>