[vtkusers] Triangulate surface points?

[Philip Fackler]

This method seems to give the bounding polydata to the unstructured volume
grid. What if the surface I'm trying to define isn't closed? Each surface
can be arbitrarily shaped.

On Fri, Mar 25, 2016 at 10:21 AM Andras Lasso <lasso at queensu.ca> wrote:

> When all points are coplanar we insert a glyph filter in the pipeline to
> add small spheres at each point.
>
>
>
> Andras
>
>
>
> *From: *Philip Fackler <philip.fackler at gmail.com>
> *Sent: *March 25, 2016 10:05
> *To: *Cory Quammen <cory.quammen at kitware.com>; Andras Lasso
> <lasso at queensu.ca>
>
>
> *Cc: *vtkusers at vtk.org
> *Subject: *Re: [vtkusers] Triangulate surface points?
> I've tried out vtkDelaunay3D some. But in cases where the surface is
> completely planar, it fails (it can't make any tets). Is there a way it can
> handle that. Sorry, I haven't had a chance to watch the video yet.
>
> On Fri, Mar 25, 2016 at 9:59 AM Cory Quammen <cory.quammen at kitware.com>
> wrote:
>
>> Cool, thanks!.
>>
>> On Fri, Mar 25, 2016 at 9:48 AM, Andras Lasso <lasso at queensu.ca> wrote:
>>
>>> It can generate non-convex surfaces up to some point - check out the
>>> video and/or try it yourself (you can install the Volume clip extension in
>>> Slicer by two clicks and you can mark points and drag them around to see
>>> how the surface is evolving). The alpha parameter in Delaunay 3D controls
>>> handling of concavities. Limitations include that a non-zero alpha may make
>>> the triangulation to fail and irregular point distances may confuse the
>>> smoothing algorithm.
>>>
>>>
>>>
>>> Andras
>>>
>>>
>>>
>>> *From: *Cory Quammen <cory.quammen at kitware.com>
>>> *Sent: *March 25, 2016 09:37
>>> *To: *Andras Lasso <lasso at queensu.ca>
>>> *Cc: *Philip Fackler <philip.fackler at gmail.com>; vtkusers at vtk.org
>>>
>>> *Subject: *Re: [vtkusers] Triangulate surface points?
>>>
>>>
>>> Andras,
>>>
>>> That's a good idea as well, but doesn't vtkDelaunay3D produce a convex
>>> hull of the input points? That's fine if your object is convex, of course,
>>> but may not give you the expected results if your object has a concave
>>> region.
>>>
>>> If there is a feature in vtkDelaunay3D that can produce concave
>>> surfaces, I would be interested to know about it.
>>>
>>> Thanks,
>>> Cory
>>>
>>> On Fri, Mar 25, 2016 at 8:34 AM, Andras Lasso <lasso at queensu.ca> wrote:
>>>
>>>> We get excellent results for sparse point sets using a combination of
>>>> vtkDelaunay3D, vtkDataSetSurfaceFilter, and vtkButterflySubdivisionFilter.
>>>> The generated surface includes the exact points that we specify.
>>>>
>>>>
>>>>
>>>> You can see what kind of surfaces you can generate from a small number
>>>> of points:
>>>>
>>>> https://www.youtube.com/watch?v=1mYNwJbE7dQ
>>>>
>>>>
>>>>
>>>> You can play with it if you download 3D Slicer and install Volume Clip
>>>> extension (
>>>> https://www.slicer.org/slicerWiki/index.php/Documentation/Nightly/Extensions/VolumeClip).
>>>> Source code is available here:
>>>>
>>>>
>>>> https://subversion.assembla.com/svn/slicerrt/trunk/VolumeClip/src/VolumeClipWithModel/
>>>>
>>>> (relevant part is in updateModelFromMarkup function)
>>>>
>>>>
>>>>
>>>> Andras
>>>>
>>>>
>>>>
>>>> *From:* vtkusers [mailto:vtkusers-bounces at vtk.org] *On Behalf Of *Cory
>>>> Quammen
>>>> *Sent:* March 24, 2016 2:29 PM
>>>> *To:* Philip Fackler <philip.fackler at gmail.com>
>>>> *Cc:* vtkusers at vtk.org
>>>> *Subject:* Re: [vtkusers] Triangulate surface points?
>>>>
>>>>
>>>>
>>>> Philip,
>>>>
>>>>
>>>>
>>>> Please take a look at
>>>>
>>>>
>>>>
>>>>
>>>> http://www.vtk.org/doc/nightly/html/classvtkSurfaceReconstructionFilter.html
>>>>
>>>>
>>>>
>>>> and
>>>>
>>>>
>>>>
>>>> http://www.vtkjournal.org/browse/publication/718
>>>>
>>>>
>>>>
>>>> I don't have direct experience with these classes, but they may have
>>>> what you need.
>>>>
>>>>
>>>>
>>>> HTH,
>>>>
>>>> Cory
>>>>
>>>>
>>>>
>>>> On Thu, Mar 24, 2016 at 2:24 PM, Philip Fackler <
>>>> philip.fackler at gmail.com> wrote:
>>>>
>>>> If someone could even definitively tell me "no, you can't do this" that
>>>> would be helpful.
>>>>
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Philip Fackler
>>>>
>>>>
>>>>
>>>> On Wed, Mar 16, 2016 at 6:24 PM Philip Fackler <
>>>> philip.fackler at gmail.com> wrote:
>>>>
>>>> Is there a way to triangulate a set of surface points using vtk? I've
>>>> looked around and everything I've found (vtk, cgal, pcl) only do a surface
>>>> reconstruction which ends up generating its own points to triangulate. I
>>>> want to actually use the points I have as the vertices of the
>>>> triangulation. Along with the point locations, I have a lot of information
>>>> available in my code that I could provide:
>>>>
>>>>
>>>> Normal vector at each point
>>>>
>>>> Bounding segmented curve(s) (i.e., lists of edge cells indexing the
>>>> list of surface points)
>>>>
>>>> A polydata representation of the surface (Note that the points I want
>>>> to triangulate are distinct from the points involved in this)
>>>>
>>>> The only vtk utility that seems to come close to this is vtkDelaunay2D,
>>>> but it's only useful if all the points can be mapped to a 2D plane. This
>>>> isn't possible in general without a parametric surface, which is one bit of
>>>> information I don't have.
>>>>
>>>> Thanks in advance for the help.
>>>>
>>>>
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>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> Cory Quammen
>>>> R&D Engineer
>>>> Kitware, Inc.
>>>>
>>>
>>>
>>>
>>> --
>>> Cory Quammen
>>> R&D Engineer
>>> Kitware, Inc.
>>>
>>
>>
>>
>> --
>> Cory Quammen
>> R&D Engineer
>> Kitware, Inc.
>>
>
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