Giles,

I think I've figured out your problem. The scalars data you sent me is an 
unstructured grid with "voxel"-type cells. One of my least favorite features of 
VTK is that there is a distinction between a box in an unstructured grid 
(called a hexahedra) and a box in a data set with structured grid (called a 
voxel). These two cells are essentially the same shape, but the order of the 
points is different.

The reason why I dislike this feature is that it is technically allowable to 
put voxel cells in an unstructured grid. However, this fouls up lots of filters 
that don't check for this corner case. Apparently the probe filter, which is 
the underlying filter for resample with dataset, is one of the filters broken 
for voxels. (Unless there is something else about this dataset that I am 
missing.) I submitted a bug about this 
(http://www.paraview.org/Bug/view.php?id=15982).

The most expedient way around this problem is to run the tetrahedralize filter 
on the scalars. That will convert the voxels to tetrahedra correctly, and the 
probe filter has no problem on that data type. The interpolation will be 
slightly different but close. Overall a better solution is to save your data as 
image data rather than convert it to an unstructured grid. The file will be 
smaller and the interpolation should happen correctly.

-Ken

From: Richardson CFD <[email protected]<mailto:[email protected]>>
Date: Saturday, February 6, 2016 at 5:54 AM
To: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>, Kenneth Moreland 
<[email protected]<mailto:[email protected]>>
Subject: [EXTERNAL] mapping scalars onto surface geometry

Kenneth,

I have made two files here available for download (sphere.stl and scalars.vtk).

https://drive.google.com/file/d/0B4bNbYR3XwvQVlBZNlVBX0RXSkU/view?usp=sharing

https://drive.google.com/file/d/0B4bNbYR3XwvQTkJxRDhLb0MxZGc/view?usp=sharing

I hope you can give these a try using "Resample with Dataset" to see what the 
problem is.

Regards Giles.
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