[vtkusers] 64bit indexing for vtkStructuredPoints issue

[David Gobbi]

Hi Jim,

I'm not sure if I understood most of your email, but here goes.

In your last paragraph when you talk about indexing using integers...
you mean when you call the vtkDataArray methods from Python, right?
Assuming that you are using VTK 5.8 or newer, and compiled with
VTK_USE_64BIT_IDS, then VTK is using extended-precision integers
on the Python side and 64-bit signed integers on the C++ side.  If you
are wondering if you should be doing some sort of casting inside
python, the answer is no.

The vtkIdType is a 64-bit signed int (type "long long").  It can't be
"unsigned long" because longs are only 32 bits on Win64 machines.

If what you're using VTK's volume rendering, then the 32-bit issues
might be in the rendering, not with the arrays.  The VTK volume
rendering in VTK 5.8 was not 64-bit safe.  I committed some patches
today that might fix this, but the jury is still out.

 - David


On Tue, Feb 21, 2012 at 10:18 AM, Jim Geach <jimgeach at physics.mcgill.ca> wrote:
>
> dear list,
>
> (note - this is a vtk python related question)
>
> i'm rendering very large grids that require 64bit indexing in the scalar component. due to a bug in the way that numpy hands over large arrays to vtk objects, i've had to come up with an inelegant solution of filling a vtkArray in a sequence of managable chunks and keeping track of the last index.
>
> this works, and tests on smaller data cubes come out looking the way they should. however, once the index exceeds MAX_INT, weird things start happening -- the resulting volume looks jumbled up, like data was placed in the incorrect position. volumes aren't completely garbled, but it's clear where discontinuities are. these effects don't occur for volumes of less than ~1024^3
>
> now, i'm indexing using long integers, but i have a feeling that this is casting is being ignored when i use InsertValue to place a value in the vtk object (i.e. vtk thinks i'm passing a standard int). the first argument to InsertValue should be a vtkIdType, but i am not explicitly casting my index as such (was assuming that vtk was interpreting and casting itself)... could this be the problem?
>
> i guess my question boils down to: how do i cast my index as the correct vtkIdType (presumably a VTK_UNSIGNED_LONG in this case)?
>
> thanks, jim