UNSTRUCTURED_GRID: Points Gaussian OK. But Contour failed.

Can ParaView render an isosurface = 1 from the UNSTRUCTURED_GRID attached? “Points Gaussian” represents it correctly (screen shot 1). But “Contour” filter fails.

Many thanks.

STEPS TO REPRODUCE ISSUE:

  1. Download UG_sample.vtk (44.2 KB)

  2. Open UG_sample.vtk in “Legacy VTK Reader”

  3. Select:

     Representation = Point Gaussian, 
     Coloring = sphere_markers, 
     Gaussian Radius = 0.04. 
    

    Result: All works as expected:
    Correctly renders data points for 8 spheres (see screen shot).
    Scalar values:

          0 = Blue = center of 8 spheres.
          1 = Yellow = points on surface of such spheres. 
          2 = Red = points in the space between spheres.
    

    UG_sample.vtk -> Information:

         Number of cells 24
         Number of points 1192
         Data range: sphere_marker float [0,2]
    
  1. Add filter: “Contour”.
    Result:
    Expected:
    - Renders isosurfaces ( = 1, for 8 spheres).
    - “Contour -> Information” same as as “UG_sample.vtk > Information”.
    Observed:
    - Renders no surfaces.
    - Contour “Information”:
    Number of cells 0
    Number of points 0
    Data range: Not available
    Output Messages:
    - None.
  1. Optional additional attempts:
    Repeat steps above for:
    - UG_minimal-VTK_VERTEX_only.vtk (5.9 KB) ,
    - UG_minimal-VTK_HEXAHEDRON_and_VTK_VERTEX.vtk (615 Bytes) , or
    - UG_minimal-VTK_POLY_VERTEX_and_VTK_VERTEX.vtk (614 Bytes)
    Result:
    Same as above (issue persists).

MY SETUP:

  - ParaView Version 5.9.0-RC2 (Dec 10 2020, from https://www.paraview.org/download/ )
  - Macbook Pro Big Sur 11.0.1 (20B29)
  - Graphics: Radeon Pro 560 4 GB

Fig. 1 UG_sample:

Fig. 2 UG_minimal-VTK_VERTEX only:

Fig. 3 UG_minimal-VTK_HEXAHEDRON_and_VTK_VERTEX:

Fig. 4 UG_minimal-VTK_POLY_VERTEX_and_VTK_VERTEX:

You can’t run isosurfaces on vertices, you need 2D or 3D cells.

My impression (I am new to ParaView) was the data controls the decision to use vertices VS other type of cell. How all that data can be represented in 2D or 3D cells?
Is there a toy sample ascii file of ANY unstructured .vtk (showing 2D or 3D cells) that successfully renders an isosurface, so I can learn?

Sure, here you go.

UG_sample_wave.vtk (1.5 MB)

Thanks for your answer, Mathieu. Issue resolved. I used Delaunay 3D filter to generate a 3D mesh from my point cloud (Poly-vertex).