Multiple .VTR files

Support
1

Hello,

I am after some guidance on where to go with my project…

I currently have a python pre processing file that reads a netCDF and generates a .vtr rectilinear grid which I then read in, to another python vtk file where I use contour filter to successfully render the isosurfaces.

However, I know want to render a ‘video’. I understand that rectilinear grid cannot take a 4th dimension or a timestep. So my pre processing file is going to have to output a .vtr file for each timestep. Is it then possible to read in many .vtr files into my visualisation app and to render them together as a video…

I understand this is not really a question, I am more looking for some pointer or guidance on how to combine multiple rectilinear grids to output my video

Thanks

2

You should try downloading ParaView then open all of the files at once as a time series. You can then press the play button in ParaView to preview the simulation and then select File->Save Animation to make a video. Here is a demo of what this looks like for a totally different data set (note I only open one file in this video but ParaView handles file series like yours with ease).

3

Hi,

This is exactly want I want to recreate but using VTK. I’ve currently got it all working in para view and can see how it should look :slight_smile:

I understand it may seem pointless what I am doing, when I can just do it para view , but it’s for my project

4

Look at the loop in this example.

You could save an image to a file in this loop. Use vtkWindowToImageFilter after the render and an image writer to save the contents of the window.
https://lorensen.github.io/VTKExamples/site/Python/IO/ImageWriter/

5

Ah, I thought this could be a bit of a programming endeavor and figured ParaView might be simpler.

We do exactly this in vtki. @S97: if you like Python, you could follow one of our gif or movie creation examples:

or do something like this (which I hacked together quickly - there should be a more elegant way to build a reader pipeline):

import vtk
import vtki

# All the VTR file names
filenames = ['foo-{}.vtr'.format(i) for i in range(4)]

reader = vtk.vtkXMLRectilinearGridReader()

def update_reader(fname):
    reader.SetFileName(fname)
    reader.Modified()
    reader.Update()

update_reader(filenames[0])
grid = vtki.wrap(reader.GetOutput())


# Create a plotter object and set the scalars to the Z height
plotter = vtki.Plotter()
plotter.add_mesh(grid, name='foo')

# setup camera and close
plotter.plot(auto_close=False)

# Open a gif
plotter.open_gif('frames.gif')

# Update Z and write a frame for each updated position
nframe = 15
for fname in filenames:
    update_reader(fname)
    print(fname)
    grid = vtki.wrap(reader.GetOutput())
    plotter.add_mesh(grid, name='foo')
    plotter.write_frame()

# Close movie and delete object
plotter.close()