[vtk-developers] potential speedup for the vtkpolydatatoimagestencil

[David Gobbi]

The vtkExtractEdges filter should do what you need, and you can
follow it with vtkStripper to ensure that the resulting polylines are
continuous.

 - David


On Tue, Feb 28, 2012 at 12:40 PM, Mark Roden <mmroden at gmail.com> wrote:
> OK, I think I see the problem here-- the gdcm loader is explicitly
> loading the data as a polygon rather than as a polyline.
>
> Is there a cheap way to convert between the two?  A simple function
> call, or a way to iterate through the data to convert it to a line so
> as to use the cheaper code path in the stenciling step?
>
> Thanks,
> Mark
>
> On Mon, Feb 27, 2012 at 1:13 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>> There is a dashboard test that uses the direct path (see the section
>> after "#test again with a contour").  It only uses a single contour,
>> but I've used vtkPolyDataToImageStencil extensively with a series
>> of contours.  The example passes the contours through vtkStripper
>> to make each contour into an ordered, contiguous polyline but I don't
>> think that step is necessary.
>>
>> http://vtk.org/gitweb?p=VTK.git;a=blob;f=Hybrid/Testing/Tcl/TestImageStencilWithPolydata.tcl;#l35
>>
>>  - David
>>
>> On Mon, Feb 27, 2012 at 2:07 PM, Mark Roden <mmroden at gmail.com> wrote:
>>> Hi David,
>>>
>>> I know where the split in the code is.  My point is that the direct
>>> path doesn't work with rtstructs, ie, the result of reading rtstructs
>>> via the vtkGDCMPolyDataReader.  It only works if I run the extrusion
>>> first.  In addition, I can't find other code that uses the direct
>>> path, so I can't see how to fix the polydata (if it's, in fact,
>>> broken) to use the direct path.
>>>
>>> So how can I get the direct path to be chosen?  The output from the
>>> reader is a set of lines, and only adds polys once we do the
>>> extrusion.  Given that it still takes 10 seconds, _something_ is being
>>> done there...
>>>
>>> Thanks,
>>> Mark
>>>
>>> On Mon, Feb 27, 2012 at 12:58 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>> On Mon, Feb 27, 2012 at 1:24 PM, Mark Roden <mmroden at gmail.com> wrote:
>>>>
>>>>> David, if you could please shed some light on how to use the faster code path-- right now, it produces blank binary images.
>>>>
>>>> See line 320 in the source code.  That's the "if" statement that
>>>> chooses the cutter-path (if the input is polys) or the direct path (if
>>>> the input is polyline contours that are aligned with the slices).
>>>>
>>>> http://vtk.org/gitweb?p=VTK.git;a=blob;f=Hybrid/vtkPolyDataToImageStencil.cxx;#l320
>>>>
>>>> If you want to be sure about what path your data is taking, you can
>>>> add print statements to the code, or run your program in a debugger.
>>>>
>>>>  - David