[Insight-developers] Nonuniform spacing transform

[Luis Ibanez]

Hi Brian,

We probably should pick a set of use cases,
and run experiments with them.

The experiments should include profiling the
run-time performance of the filters.

I'm a bit skeptical of adapting every filter in
ITK to images that are not using regular
orthogonal grids.

It would seem that just providing a resampling
filter that efficiently map irregular images to
regular ones should take care of the problem.


      Luis


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On Sat, Oct 16, 2010 at 3:19 PM, brian avants <stnava at gmail.com> wrote:

>   hmm. i wasnt actually proposing anyone try to make every image
> filter in itk work on meshes, though working on point sets with
> topological neighborhoods would encapsulate most of the non-uniform
> cases i've seen discussed ... + in the context of the image
> refactoring stuff, it seems a similar problem.   that is, in
> permitting a non-uniform neighborhood connection, the data object
> becomes very similar to a mesh.   if you want to know how to do a
> mathematical operation on a mesh (or an image with a non-uniform
> neighborhood) there are new implementation questions that come up.
> for instance, the field of finite elements was largely developed in
> order to deal, in a general way, with domain representations that are
> non-uniform.   that is, finite difference solutions break down in
> those domains.   when i look at this page (
> http://www.itk.org/Wiki/ITK_Release_4/Image_Class_Hierarchy_Refactoring
> ) ,  i see many filters listed at the bottom of the page that need to
> be "fixed" to deal with non-linearities in spacing.    it's just not
> clear how that can be done without using FEM or some other systematic
> approach to model the regular-to-irregular grid transformations.
> alternatively, if you first apply a transformation to an image that
> factors out the nonlinearity, then you are ok with most of the
> standard operations that exist it itk.    you can then transform the
> output of the linear-space filter operation back to the nonlinear
> space.   maybe this is a reasonable alternative to trying to fix each
> filter to work with some unknown amount of nonlinearity in spacing?
>
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