VTK File not displaying colours and only showing as Point Gaussian

ParaView Support
1

Hi, I generated the following VTK file from a simulation in FiPy and reading it in Paraview doesnt seem to be working. I am only able to view the points as a Point Gaussian and the colours are not suitably reflected. 50.0_output.vtk (24.7 KB)

I would appreciate any insight on this and is it possible to modify the VTK files in a scripted fashion so I could run a postprocessing pipeline to correct the VTK files if there is an error or are there certain buttons in Paraview that I need to click.

Thanks for your help.

2

It is because of the cell type used in your dataset.

In your file, from line 557 to 956 (i.e the ‘CELL_TYPES’ part) try replacing 41 (convex point set) by 9 (Quad). See here https://vtk.org/doc/nightly/html/vtkCellType_8h.html for available values, and check vtkCell subclasses (https://vtk.org/doc/nightly/html/classvtkCell.html) to get more informations.

more details

ParaView (and VTK) does not display points directly but only cells. ParaView does not handle every kind of VTK cells. The Point Gaussian is a workaround to display a geometry at each point, whatever the cell type of the dataset.

1 Like
3

Hi! For future reference if anyone comes across a similar problem, here is a crude script in python to quickly modify the .vtk file. I know its not the most elegant, but it does the trick. I essentially do a text replacement of the 41 to 9.

import glob

from tempfile import mkstemp
from shutil import move
from os import remove

# Obtain list of VTK files in directory
vtk_list = glob.glob("*.vtk")

# Rename the extensions to .txt files to process
for vtk in vtk_list: 
    # Access the last four characters in the path and replace them with .txt
    os.rename(vtk, vtk[:-4] + ".txt")

txt_list = glob.glob("*output.txt")

def replace(source_file_path, pattern, substring):
    fh, target_file_path = mkstemp()
    with open(target_file_path, 'w') as target_file:
        with open(source_file_path, 'r') as source_file:
            for line in source_file:
                if line.strip() == pattern:
                    lineout = f"{substring}\n"
                    target_file.write(lineout)
                else:
                    target_file.write(line)
    remove(source_file_path)
    move(target_file_path, source_file_path)

for text in txt_list:
    replace(text, "41", "9")
    os.rename(text, text[:-4] + ".vtk")
4

On the command line, there are some powerful tools to do such replacements, as sed:

$ sed -i 's/^41$/9/' 50.0_output.vtk