Resample to Dataset terminology


(Dennis Conklin) #1

Am I the only person who can never remember the difference between Input and Source when using this filter? I always have to look it up. Could we possibly relabel these as “Input Variables” and “Source Geometry” or would that make it too easy?

Irritatingly yours,

Dennis :wink:


(Kenneth Moreland) #2

You are not the first to bring this up (https://gitlab.kitware.com/paraview/paraview/issues/12257), but thanks for bringing it up to help raise the priority.


(Walter Alan Scott) #3

Changed target to this spring release, marked as required. Oh, Dennis, you are sooo very correct.


(Dennis Conklin) #4

In Kitware’s defense, I have just discovered the tips if you hover over the fields which clue us in!


(Dennis Conklin) #5

How about a legitimate question about Resample to Dataset.

I am trying to take a cylindrical membrane surface and Resample it’s variables onto a copy of it that has been rotated.
So, Input is the original cylinder, which is discretized every 2 degrees, and Source is a copy of the original cylinder that has been rotated by 0.5 degrees.

The "Compute Tolerance has to be increased to 0.02 in order to get a reasonable distribution on the rotated geometry. What is this tolerance, is it a physical distance, and how do I determine a reasonable value a priori? What bad things would happen if I used a non-optimized value (i.e., too large of a tolerance)?

The Computed Tolerance must be very small because I get a very bad distribution on the rotated geometry (almost single value)

Thanks for any help.
Dennis


(Kenneth Moreland) #6

Trying to sample values from a surface is always problematic as an x, y, z coordinate will seldom be exactly on a surface. In fact, in your case, none of your coordinates will be exactly on the surface. When you rotate your cylinder 0.5 degrees, the resulting points will deviate off the chords joining the 2 degree samples in the original mesh.

Choosing a tolerance is always problematic. Too small of a tolerance (particularly on surfaces) and points won’t be identified in the cells you want them to be. But too large of a tolerance and you might be sampling values in a mesh where you shouldn’t be. I wasn’t privy to the decisions in deciding what the computed tolerance should be, but I believe it picks small numbers to error towards only sampling points truly in cells.

You will have to play with the tolerance until it gives you the results you like. I also found that changing the Cell Locator to Tree Cell Locator seemed to improved performance.


(Dennis Conklin) #7

Ken,

In my case, where I have a 1-to-1 correspondence of nodes/elements with slight displacement between the two structures, it doesn’t seem to change anything if I change Tolerance from 0.02 to 1000.0. I assume this is because it uses the closest point no matter what.

Since I am trying to write a general purpose routine which will be used on meshes of undetermined size and refinement, I think my only possible problem is having Tolerance too small, so by using 1000.0 I avoid this problem. I am always remapping onto an identical but slightly perturbed mesh, so that is my plan unless you can see a potential pitfall.