Contour works inproperly

ParaView Support
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1

Dear All,

I am trying to draw a contour from Octree mesh, which is saved in an Unstructured Grid format(points in vertex, variables in cells. Each cell knows the neighbors ).
Would you give me a hint on how to plot contour wisely?

I am suffering from this problem for almost 2 years. Thus, I tried 3 things:

  1. Directly plot contour from my source data, As a result, I have holes in my contour plot
    Screen Shot 2020-09-04 at 13.23.46
    Screen Shot 2020-09-04 at 13.23.462880×1800 799 KB
  2. ApplyCellsToPoint filter and then use contour filter, and I observe the same holly picture
    Screen Shot 2020-09-04 at 13.26.26
    Screen Shot 2020-09-04 at 13.26.262880×1800 780 KB
  3. ApplyCellsToPoint filter, then Delauneu3D filter and then use contour filter, and I see a normal picture:
    Screen Shot 2020-09-04 at 13.36.32
    Screen Shot 2020-09-04 at 13.36.322880×1800 723 KB

    The only disadvantage of this trick is spending an enormous time for Delauneu3D. I am showing the results on the coarse mesh, but in refined mesh, it takes forever.
    Maybe there is a method of how to obtain a coarse mesh for Delauneu3D?

I have a 4th way, but I don’t know how to implement it. The idea is the following: I interpolate my data to the uniform coarse mesh and then try to plot contour. I noticed that such artifacts happen only in a place where a high value of the ratio between neighboring cell size(transition from refined mesh to coarser mesh). What filter should I use to interpolate my data to the uniform mesh? Or it is possible only using scipy, numpy, i.e. outside of paraview?
Can be It done in parallel?

Thank you in advance!
Best regards,
Evgenii

2

The octree mesh you have initially is regular. Does it make sense for you to transform it into a regular grid instead of an unstructured mesh ? This could be done with a resample to image for example.

Then, you can try to extract a contour as you do with the unstructured mesh if you want to do processing with this contour.
Otherwise, if you are only interested in visualizing this contour, you may use the Volume representation of your 3D image and in the Display Property select the Blend Mode “Isosurface”. This way, the contour is extracted in GPU which should be much faster.

3

It’s tough to say what is going on without having a better understanding of the data. Could you share the dataset?

4

Dear Charles,
Thank you for your helpful advice, indeed to get a nice picture I did:
my_source =>
clip interesting region =>
convert cell to point (otherwise I have a cubic shape surfaces) =>
resample to image =>
- contour
- tracer
- , etc

3108×1168 571 KB

Best regards,
Evgenii

5

Dear Cory,

Thank you for your willingness to help me!)
the link to data is put in GDrive
It can be helpful to debug a contour filter.

Best regards,
Evgenii