[vtk-developers] vtkSurfaceReconstructionFilter

[Tim Hutton]

Hi Ken,

Appreciate that knowing the size of the output volume before it is produced 
could be useful, but I can't see how this is really possible at the moment. 
Ideally the user doesn't normally set SampleSpacing when using the filter 
(though maybe this isn't clearly explained) - the method of using the 
number of points relative to the volume of the bounding box pointset seems 
to work well at giving a reasonable sampling. I'd be happy for it to be 
replaced with SetSampleDimensions (since the spacing is just the bounding 
box divided by the dimensions) but not for the dimensions to default to 
some fixed value, this really does change the function of the filter.

Maybe it would be more useful (and would better match its name) if 
vtkSurfaceReconstruction ran vtkContour over the volume before outputting a 
polygonal surface, rather than a volume. Inevitably this is what is done 
after running vtkSRF anyway. This would solve your problem - the volume 
would be only an intermediate memory use.

Having said that, the filter doesn't work terribly well at doing surface 
reconstruction, it's an old algorithm. I'd love to replace it with 
PowerCrust or something similar but we're having trouble porting the code 
compactly to VTK at the moment.

Tim.

At 14:49 19/06/2002 -0400, you wrote:
>Hey Folk,
>
>Does anyone have an opinion on the API to
>vtkSurfaceReconstructionFilter? Specifically this filter uses a
>SetSampleSpacing to determine how many samples to take and what their
>spacing should be. It defaults to -1 to indicate that it should be
>automatically computed. I'd like to change this to match some of the
>other filters in VTK. Other volumetric sources us SetSampleDimensions
>to specify how many samples to take and then they compute what the
>spacing should be. This is the opposite of vtkSurfaceReconstruction
>filter. The advantage of setting the SampleDimensions is that the size
>of the output volume and its memory footprint can be computed in
>ExecuteInformation from the SampleDimensions but not from the
>SampleSpacing (because it doesn't know the bounds of the input in
>ExecuteInformation). So...  I'd like to add SetSampleDimensions which
>would default to some reasonable size.  I can leave in
>SetSampleSpacing which if set would override the SampleDimensions. The
>only change in behavior would be if you were using
>vtkSurfaceReconstrucitonFilter and were not setting the SampleSpacing
>the dimensions of the output volume might change from what you are
>currently getting.
>
>Comments?
>
>Thanks
>Ken
>
>--------------------------
>Ken Martin, PhD
>Kitware Inc.
>518 371-3971 x101
>469 Clifton Corporate Pkwy.
>Clifton Park, NY 12065
>
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Tim Hutton,                        http://www.eastman.ucl.ac.uk/~dmi/MINORI
Research Fellow & PhD student,                   T.Hutton at eastman.ucl.ac.uk
MINORI Project, Biomedical Informatics Unit,     Tel: [+44] (0)20 7915 2344
Eastman Dental Institute, UCL,                   Fax: [+44] (0)20 7915 2303
256 Gray's Inn Road, London WC1X 8LD, UK      Mobile: [+44] (0)7748 678 832
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