[vtkusers] vtkCutClosedSurface

[David Gobbi]

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
>>>
>
>