[vtkusers] Fwd: Unsure how to use vtkDelaunay3D

[vtk matt]

Alright well as long as that's the expected behavior then I guess I'm
satisfied.  I was able to work around it by creating a new
vtkUnstructuredGrid for every tetrahedron and then creating actors from
those...  Not pretty but it got me the sanity check I was looking for.
Thanks for the help.

On Mon, Jun 1, 2015 at 6:06 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> That's what the vtkDataSetMapper does when it renders: if it's input is a
> 3D mesh, then it just renders the surface.  You'd probably need to use
> something like vtkExtractEdges to turn it into a space-filling wireframe.
>
> I don't do much mesh work with VTK, so hopefully someone else can chime in
> with different ways to render 3D meshes.
>
>  - David
>
> On Mon, Jun 1, 2015 at 7:00 PM, vtk matt <vtkmatt at gmail.com> wrote:
>
>> Yeah this was my understanding.  Any idea then why I only see surface
>> triangles when I render it?  I set my actor to wireframe mode and I see no
>> internal structure.  Maybe this is just a visualization thing?  With the
>> info you provided I did iterate across all cells and cast them to type
>> vtkTetra and they all have four faces which is good.  It would be great to
>> see this visualized though as a sanity check that I do in fact have
>> tetrahedrons.  Thanks again.
>>
>> On Mon, Jun 1, 2015 at 5:52 PM, David Gobbi <david.gobbi at gmail.com>
>> wrote:
>>
>>> The documentation for vtkDelaunay3D says that it outputs only
>>> tetrahedrons unless you specifically set the "Alpha" value (I'm not 100%
>>> sure what "Alpha" is for, but since you aren't using it, I don't think you
>>> need to worry about it).
>>>
>>>  - David
>>>
>>> On Mon, Jun 1, 2015 at 6:19 PM, vtk matt <vtkmatt at gmail.com> wrote:
>>>
>>>> Hi David,
>>>>
>>>> Thanks for the clarification.  I
>>>> ran tets->GetOutput()->GetNumberOfElements(vtkDataObject::CELL) and got a
>>>> value of 18 for my input which would make sense as the number of
>>>> tetrahedrons.  Do you know if I can expect these cells to in fact contain
>>>> tetrahedrons then?
>>>>
>>>> --Matt
>>>>
>>>> On Wed, May 27, 2015 at 8:17 PM, David Gobbi <david.gobbi at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi Matt,
>>>>>
>>>>> You've been misled by VTK's rather terse documentation:
>>>>>
>>>>>   Get the number of elements for a specific attribute type (POINT,
>>>>> CELL, etc.).
>>>>>
>>>>> For a mesh, you can call GetNumberOfElements(vtkDataObject::POINT) or
>>>>> you can call GetNumberOfElements(vtkDataObject::CELL).  Those are the only
>>>>> two choices.  You can't ask for a particular type of cell, all you can do
>>>>> is ask it to return the total number of cells.
>>>>>
>>>>>  - David
>>>>>
>>>>> On Wed, May 27, 2015 at 5:41 PM, vtk matt <vtkmatt at gmail.com> wrote:
>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> I have spent the past few days trying to figure out how to use
>>>>>> vtkDelaunay3D properly and decided I'd better seek out some help.  My goal
>>>>>> is relatively straight-forward:  Given a set of points in 3D, generate a
>>>>>> tetrahedral mesh, and use the results to determine which tetrahedron
>>>>>> contains an arbitrary point.
>>>>>>
>>>>>> In its simplest form I am doing the following:
>>>>>>
>>>>>> vtkSmartPointer<vtkDelaunay3D> tets =
>>>>>> vtkSmartPointer<vtkDelaunay3D>::New();
>>>>>> tets->SetInput(points);
>>>>>> tets->Update();
>>>>>> printf("Number of tets: %d\n",
>>>>>> tets->GetOutput()->GetNumberOfElements(VTK_TETRA));
>>>>>>
>>>>>> The output claims there are zero tetrahedrons.  However if I render
>>>>>> an actor from tets->GetOutput(), I am able to visualize a wireframe surface
>>>>>> mesh, so I know it's doing something.
>>>>>>
>>>>>> So I guess my questions are the following:  Why does the output not
>>>>>> contain any tetrahedrons?  Why does the mesh only show surface triangles?
>>>>>> Ultimately what is the proper way to construct a tetrahedral mesh such that
>>>>>> I can query which tetrahedron contains an arbitrary point?
>>>>>>
>>>>>> Thanks.
>>>>>>
>>>>>> --Matt
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>
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