[vtk-developers] 64-bit indexing of vtkImageData

[Ken Martin]

> 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.

In general this sounds good and makes sense. Certainly increments (and
related number of cell type values) should be vtkIdType. 

You are right that extents/coordinates are more of a question. We clearly
should support images with more than range-of-int cells. Do we want to
support datasets that have more than range-of-int pixels on a side? Beats
me. I have a hard time imagining an image that is more than 2 gigapixels on
one axis but maybe others have comments ideas?

Ken