[vtkusers] vtkImageImport -> cell data

[David Gobbi]

Hi Martin,

In VTK, image data is point data, one data value per point.  Cell data
isn't used because the vtkVoxel cell is not a voxel in the conventional
sense: a vtkVoxel is a finite element that connects 8 points, where each
corner point generally has a data value (use of point scalars in VTK is
much more common than the use of cell scalars).  So the typical usage of
vtkVoxel is contrary to the conventional definition of "voxel" which has
just one data value.

The VTK image processing filters work on point data, because a VTK point
fits the conventional definition of "voxel" (i.e. a voxel defined as one
data sample in a volumetric grid of such samples) better than vtkVoxel does.

 - David

On Mon, Jan 18, 2016 at 4:27 AM, Martin Genet <
martin.genet at polytechnique.edu> wrote:

> Hey everyone,
>
> I'm realizing that vtkImageImport generates images with point data, not
> cell data—the Detailed Description says "The array applies on scalar point
> data only, not on cell data." I was wondering why? I would expect it to
> read the data as cell data, with one value per voxel. Thanks for helping to
> understand!
>
> Martin
>
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