[vtkusers] grid reslice

[Young, Ryan]

Hey.

I made a little pdf to hopefully clear things ups.   Just to summarize, I have a vector field that is the displace of a volume.  The test case is just a vector pointing 15 units in the x direction .  It is only define for voxels within the volume.  I am using a vtkGridTransform and vtkImageReslice to apply this transformation.  The result should a the volume unchanged, but centred 15 voxels to the right.  What I am seeing is that the left half of the volume is missing.

If I define the transformation to exist every voxel, not just within the volume, it works as expect and the volume is moved to the rigth 15 units.

I created a repo with two scripts that show this.  Its at https://bitbucket.org/youngre/vtk_grid_transform/

Thanks again,
Ryan



________________________________
From: David Gobbi [david.gobbi at gmail.com]
Sent: Tuesday, January 27, 2015 1:49 PM
To: Young, Ryan
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] grid reslice

Hi Ryan,

I still don't know what I'm looking at.  Especially when the two images are at completely different scales (the deformed image is ridiculously small).  Maybe you can annotate them?

 - David

On Tue, Jan 27, 2015 at 2:33 PM, Young, Ryan <Ryan.Young at seattlechildrens.org<mailto:Ryan.Young at seattlechildrens.org>> wrote:


Sure.  I used a slight larger (15 voxel in the x direction) deformation so that the effect is drastic.

Thanks again,
Ryan

________________________________
From: David Gobbi [david.gobbi at gmail.com<mailto:david.gobbi at gmail.com>]
Sent: Monday, January 26, 2015 6:18 PM
To: Young, Ryan
Cc: vtkusers at vtk.org<mailto:vtkusers at vtk.org>
Subject: Re: [vtkusers] grid reslice

Hi Ryan,

Can you attach your image both with and _without_ deformation?
I looked at the image but couldn't make any sense of it.

 - David


On Mon, Jan 26, 2015 at 6:29 PM, Young, Ryan <Ryan.Young at seattlechildrens.org<mailto:Ryan.Young at seattlechildrens.org>> wrote:
Hello,

I have a vector field that has the displacement vector for each voxel in a volume.  I am trying to apply this deformation and visualize the results.  The difficulty I am have is that the deformation only exist for the voxels inside the volume, not globally in the whole space. If I set the displacement to zeros outside the volume I get poor results.

My toy example is just do to a 10 voxel shift in the x direction The volume is padded with zeros so there is plenty of room.  The result is an image missing about ten voxels.  See attached picture.  If I make a similar deformation that exist at all voxels, the result is as expect.  Any advice. Also, a code snippet is below.

Thanks in advanced
Ryan

grid=vtk.vtkGridTransform()
grid.SetDisplacementGrid(defImporter.GetOutput())
grid.SetInterpolationModeToLinear()

reslice=vtk.vtkImageReslice()
 reslice.SetWrap(1)
 reslice.SetResliceTransform(grid)
 reslice.SetInterpolationModeToLinear()
 reslice.SetOutputSpacing(1,1,1)
 reslice.SetOutputOrigin(0,0,0)
 reslice.SetInputConnection(volImporter.GetOutputPort())
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