Tesselate filter on polygon indicates no parametrization

Development
1

The “Tesselate” filter applied on “VTK_POLYGON” indicates “Input dataset has cells without parametization”. Example file:

# vtk DataFile Version 3.0
Generated by Hand
ASCII
DATASET UNSTRUCTURED_GRID
POINTS        14 double
 0.0 0.0 0.001
 0.0 0.0 0.002   1.0 0.0 0.0
 1.0 1.0 0.0     0.0 1.0 0.0
 2.0 0.0 0.0     2.0 1.0 0.0
 0.5 0.1 0.0     1.0 0.6 0.0
 0.6 1.1 0.0     0.1 0.4 0.0
 2.0 -0.5 0.0    1.0 -1.0 0.0
 0.0 -0.6 0.0
CELLS       2      12
4  2 5 6 3
6  1 13 12 11 5 2
CELL_TYPES      2
9
7
POINT_DATA         14
FIELD FieldData 1
TempNode 1      14 float
  0.0               
  0.0   1.5
  0.2   0.0
  1.0   0.4
  2.0   0.5
  0.25  0.15
  0.25  0.45
  0.13
2

Use Triangulate filter before using Tesselate.

3

The “Triangulate” filtre is grey’ed (not applicable) on my Ubuntu 22.04 Paraview 5.10.0-RC1.
Example below, even with a simple quad.

# vtk DataFile Version 3.0
Generated by Hand
ASCII
DATASET UNSTRUCTURED_GRID
POINTS        4 double
 1.0 0.0 0.0  2.0 0.0 0.0  2.0 1.0 0.0  1.0 1.0 0.0
CELLS       1      5
4  1 2 3 0
CELL_TYPES      1
9
POINT_DATA         4
FIELD FieldData 1
TempNode 1      4 float
  1.5  1.0  2.0  0.5
4

Use “ExtractSurface” first if you want to work with surface, or use “Tetrahedralize” instead.

5

OK thanks. But it cannot be applied on quadratic elements at the same time.

6

please share your data.

7 
# vtk DataFile Version 3.0
Generated by Hand
ASCII
DATASET UNSTRUCTURED_GRID
POINTS        21 double
 0.0 0.0 0.001
 0.0 0.0 0.002   1.0 0.0 0.0
 1.0 1.0 0.0     0.0 1.0 0.0
 2.0 0.0 0.0     2.0 1.0 0.0
 0.5 0.1 0.0     1.0 0.6 0.0
 0.6 1.1 0.0     0.1 0.4 0.0
 2.0 -0.5 0.0    1.0 -1.0 0.0
 0.0 -0.6 0.0    -1.0 0.0 0.0
 -0.5 0.5 0.0    -0.5 0.0 0.0
 2.5 0.0 0.0     2.3 0.8 0.0
 2.4 1.5 0.0     1.9 1.5 0.0
CELLS       5      35
8  1 2 3 4 7 8 9 10
4  2 5 6 3
6  1 13 12 11 5 2
6  4 14 1 15 16 10
6  5 17 18 19 20 6
CELL_TYPES      5
23
9
7
22
7
CELL_DATA         5
SCALARS material int
LOOKUP_TABLE default
1
2 2 2
3
FIELD FieldData 1
TempCell 1      5  float
  0.0               
  0.4 0.1 0.2               
  0.3              
POINT_DATA         21
FIELD FieldData 1
TempNode 1      21 float
  0.0               
  0.0   1.5   0.2   0.0   1.0
  0.4   2.0   0.5   0.25  0.15
  0.25  0.45  0.13  0.21  0.41
  0.17  0.23  0.45  0.06  0.28
8

Tetrahedralize + Tesselate works fine on your data:

image
image1549×1540 130 KB

9

Yes, but I think the point is that that Tetrahedralize (or ExtractSurface + Triangulate) do not offer an option for how finely to subdivide higher-order cells, so you are always left with a coarse subdivision for higher-order cells should you need to triangulate polygons.

I don’t know how much work it would take to provide a “non-linear subdivision level” to the Tetrahedralize and Triangulate filters.

1 Like
10

That’s the point.
Initially, I thought the Tesselate operator, that works on triangles and quads, could also apply on polygons.