[vtk-developers] 64-bit indexing of vtkImageData

David Gobbi dgobbi at atamai.com
Tue Jan 18 12:24:30 EST 2005


Hi Bill,

The VTK 4.4 changes did not involve either internal or external API
changes.  Unlike the changes I propose for VTK cvs, the VTK 4.4
increments are still stored in 32-bit ints, but they are cast to
vtkIdType before they are used in indexing computations.  Hence, each
slice can only have 2 gigavoxels since the 32-bit Z increment can't
support more, but it works dandy on the visible female data where the
volume as a whole is larger than the 32-bit limit.

In any case, I won't commit the changes to the VTK 4.4 branch unless
a significant number of people see a real value in doing so.  I can
understand that you also fear the possibility of something called "bugs,"
particularly in a stable branch.

 - David


On Tue, 18 Jan 2005, Lorensen, William E (Research) wrote:

> David,
>
> As for VTK 4.4, I don't think we can tolerate any internal/external API
> changes.
>
> Bill
>
> -----Original Message-----
> From: David Gobbi [mailto:dgobbi at atamai.com]
> Sent: Monday, January 17, 2005 5:17 PM
> To: vtk-developers at public.kitware.com
> Subject: [vtk-developers] 64-bit indexing of vtkImageData
>
>
> Hi All,
>
> When VTK was switched over to vtkIdType so that 64-bit indices into data
> arrays became possible, vtkImageData was overlooked and even in VTK 4.5 it
> isn't possible to have image data over the 32-bit size limit.
>
> I'd like to add 64-bit image indexing before VTK 5 is released, and I
> want to solicit comments about how aggressive the change should be.
> I think that the best approach is for increments to be stored as
> vtkIdType, but perhaps extents and any image integer coordinates should
> also be converted to vtkIdType.  It isn't absolutely necessary for
> extents to be stored as vtkIdType unless people will be dealing with
> images that are more than two gigavoxels across in one of the three
> dimensions.
>
> Any thoughts?
>
> Also, Glen Lehmann has finished a conversion of VTK 4.4 to 64-bit
> image indexing, and we might be able to release it to the public in
> the near future.  Would anyone be interested?  I could even commit
> it to the VTK 4.4 branch, since the changes didn't involve any of
> the header files.
>
> --
>   David Gobbi, PhD
>   Lead Software Developer
>   Atamai Inc. (www.atamai.com)
>
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