[vtkusers] image with variable spacing

[David Gobbi]

Hi Miro,

There is no easy way to work with images that have variable sampling.
You will almost certainly have to create your own widgets in order to
get the kind of user interaction that you are looking for.  However, I
have some suggestions on how to at least get the data to render
properly:

1) You will definitely need to use one vtkImageData object per
segment, given the restrictions on vtkImageData.

2) Likewise, each segment will need to have its own mapper (I suggest
using the vtkImageResliceMapper, but of course I'm biased towards it
because I wrote it).

3) The mappers for each segment will have to be synchronized to each
other.  For vtkImageResliceMapper, this can be done by using the same
SlicePlane for all the mappers, or alternatively by using
SliceAtFocalPoint/SliceFacesCamera and controlling the slicing via the
camera position and focal point.

4) You will have to fill in the gaps between the segments.  One
quick-and-dirty way of doing this with vtkImageResliceMapper is to
call SetBorder(1) to slightly extend the rendered bounds of the image.

As I mentioned in my first paragraph, none of this will work with
vtkResliceCursorWidget, you'd have to write your own user interaction
code.

  David


On Tue, Nov 19, 2013 at 12:46 AM, Miroslav Drahos <MDrahos at robodoc.com> wrote:
> Hi,
> I am working with medical image (a 3D volume) that consists of several segments with different spacing in z-direction. I was hoping to get an opinion on how to work with this data; I need to be able to visualize it all at once, and reslice it at arbitrary direction.
> One quite natural idea was to resample the image and then work with it as one vtkImageData object, use vtkResliceCursorWidget on it, etc. However, the origin of the individual image segments changes too, and the gap between them is not an integer multiple of z-resolution, so I can't fit an integer number of (empty) slices between the segments, and the origin will be shifted.
> The other idea that I am about to implement is to store a vector of images, and dynamically re-plug the reslice cursor to the segment that it is currently on, and have multiple representations that would copy their parametric plane representation from the active on and display several planes with their own textures.
> But it just seems so clumsy, and makes me feel there must be a more elegant and efficient solution.
> I have seen vtkRectilinearGrid, but that cannot be plugged into a reslice cursor.
>
> Anybody has an idea of how to work with such data?
> Thank you very much,
> Miro