[Insight-users] Computing 3D coordinates from 2D slice

[Daanen Vincent]

Hi Itk users,

I'm facing to a problem I don't understand.

I have a 3D image with is not aligned with axis. From this 3D image, I
extract a slice with itkExtractImageFilter.
I want to check that PhysicalPoint computed from 3D image and 2D image are
correct with each other.

To make it clearer, let me give an example: 
 1) From 3D image, I extract an axial slice (say number 10) which gives me a
2D-Slice
 2) I compute Index2PhysicalPoint from 3D image with index = (x,y,10)  	-->
PhysPointFrom3D
 3) I compute Index2PhysicalPoint from 3D Slice with index=(x,y)
--> PhysPointFrom2D
 4) I check that PhysPointFrom3D == PhysPointFrom2D

I think this makes sense.

The problem I have is that using Index2PhysicalPoint from a 2D slice gives
as a result a 2D point ! I can't undestand this. According to me, a 2D
oriented slice transform a pixel (i.e 2D index) in a 3D real point

So I guess I missed something but I can't point out this think.

Could anybody help me to make this clearer ? 

Thanks

 Vince