[vtk-developers] potential speedup for the vtkpolydatatoimagestencil

[Mark Roden]

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