Using vtkProbeFilter to sample values of NIFTI volume onto surface

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Using vtkProbeFilter to sample values of NIFTI volume onto surface

Michael Jordan
Hi,

i have a fMRI NIFTI volume whereby each voxel value corresponds to a statistical value indicating the activation. I am using the vtkProbeFilter to show the activation on the
corresponding brain surface. The results looks pretty good but I would like to understand what is really going on when using the vtkProbeFilter.

Assumed that I specify a tolerance value of <a href="tel:+49100" style="color:rgb(0,114,198)">10.0, how the filter determines the corresponding scalar value for a certain surface vertex?
Is the filter simply assigning the value of the closest voxel to the vertex? Or is the filter averaging all values within the specified tolerance?

Thank you!

Regards, Michael

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Re: Using vtkProbeFilter to sample values of NIFTI volume onto surface

VTK - Users mailing list
Hi Michael,

In this case, for each vertex in the surface mesh, the filter finds the voxel within which the vertex falls and interpolates the points values of the 8 points of the voxel on to the vertex. The tolerance is used for dealing with floating point errors. It specifies the tolerance to use when a vertex is near the boundary of a cell to determine if it should be considered to be inside the cell.

Thanks
Sujin


On Sat, Feb 23, 2019 at 6:59 PM Michael Jordan <[hidden email]> wrote:
Hi,

i have a fMRI NIFTI volume whereby each voxel value corresponds to a statistical value indicating the activation. I am using the vtkProbeFilter to show the activation on the
corresponding brain surface. The results looks pretty good but I would like to understand what is really going on when using the vtkProbeFilter.

Assumed that I specify a tolerance value of <a href="tel:+49100" style="color:rgb(0,114,198)" target="_blank">10.0, how the filter determines the corresponding scalar value for a certain surface vertex?
Is the filter simply assigning the value of the closest voxel to the vertex? Or is the filter averaging all values within the specified tolerance?

Thank you!

Regards, Michael
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