CFD Online Discussion Forums - [OpenFOAM] Exporting screenshots from paraview with pvbatch

Hello there,

I'm running simulations via VPN+ssh on a remote computer. Therefore, viewing results with the ParaView-GUI isn't really an option. That's why I wrote a pvbatch (python) script to load VTK files, take screenshots of the results of the quantity alpha (particle volume fraction) and export them as .png files.
This is my code:

Code:

import sys

import os



print("Running batchExport.py ...")



# set current path as case path

casePath = os.getcwd()



# extract caseName from path

caseName = casePath.replace('/', 'X', casePath.count('/') - 1)

caseName = caseName[(caseName.find('/') + 1):]



# add trailing slash

casePath = casePath + '/'



# first argument contains number of frames

frames = int(sys.argv[1])



# second argument contains time step

step = float(sys.argv[2])



try: paraview.simple

except: from paraview.simple import *

paraview.simple._DisableFirstRenderCameraReset()



AnimationScene1 = GetAnimationScene()

AnimationScene1.EndTime = (frames-1)*step

AnimationScene1.PlayMode = 'Snap To TimeSteps'



RenderView1 = GetRenderView()



# declare list for filenames

files = []



for i in range(frames):

   # define file names

   file = casePath + 'VTK/' + caseName + '_' + str(int(i*step)) + ".vtk"

   # append file name to list for VTKReader

   files.append(file)



#read files

reader = LegacyVTKReader( FileNames=files )



DataRepresentation1 = Show()

DataRepresentation1.EdgeColor = [0.0, 0.0, 0.5]

DataRepresentation1.SelectionPointFieldDataArrayName = 'alpha'

DataRepresentation1.SelectionCellFieldDataArrayName = 'alpha'

DataRepresentation1.ScalarOpacityUnitDistance = 0.004

DataRepresentation1.ExtractedBlockIndex = 2

DataRepresentation1.ScaleFactor = 0.02



RenderView1.CenterOfRotation = [0.04, 0.05, 0.025]



RenderView1.CameraPosition = [0.04, 0.05, 0.4522]

RenderView1.CameraFocalPoint = [0.04, 0.05, 0.025]

RenderView1.CameraClippingRange = [0.373175, 0.5]

RenderView1.CameraParallelScale = 0.110567



a1_alpha_PVLookupTable = GetLookupTableForArray( "alpha", 1, RGBPoints=[0.0, 0.0, 0.0, 1.0, 0.635, 1.0, 0.0, 0.0], VectorMode='Magnitude', NanColor=[0.498039, 0.498039, 0.498039], ColorSpace='HSV', ScalarRangeInitialized=1.0, LockScalarRange=1 )



a1_alpha_PiecewiseFunction = CreatePiecewiseFunction( Points=[0.0, 0.0, 0.5, 0.0, 0.635, 1.0, 0.5, 0.0] )



DataRepresentation1.ScalarOpacityFunction = a1_alpha_PiecewiseFunction

DataRepresentation1.ColorArrayName = ('CELL_DATA', 'alpha')

DataRepresentation1.LookupTable = a1_alpha_PVLookupTable

DataRepresentation1.ColorAttributeType = 'CELL_DATA'



ScalarBarWidgetRepresentation1 = CreateScalarBar( Title='alpha', LabelFontSize=12, Enabled=1, LookupTable=a1_alpha_PVLookupTable, TitleFontSize=12 )

GetRenderView().Representations.append(ScalarBarWidgetRepresentation1)



a1_alpha_PVLookupTable.ScalarOpacityFunction = a1_alpha_PiecewiseFunction

AnimationScene1 = GetAnimationScene()



print('Exporting...')



for i in range(frames):

    print('Current frame: ' + str(i) + '/' + str(frames - 1))

    AnimationScene1.AnimationTime = float(i*step)

    Render()

    WriteImage(casePath + 'Animation/' + str(i*step) + '.png')

Now, this works well enough for me, which is why I wanted to share the code. Keep in mind that you still need to feed it with arguments for the number of frames to export (= number of VTK files to read from) and the time step between them (has to be consistent). This bash script is how I call the pvbatch script:

Code:

#!/bin/bash



# for VTK conversion, reconstruct data

reconstructPar



# convert binaries to VTK (I excluded all patches to only get internalField)

foamToVTK -fields '(alpha)' -excludePatches '(inandouthalf11 inandouthalf12 inandouthalf21 inandouthalf22 top walls frontAndBackPlanes)' -useTimeName



# remove reconstructed data

foamListTimes -rm -noZero -time 0:



# get number of time steps written

timeSteps=$(foamListTimes -withZero -processor | wc -l)



# get latest time

latestTime=$(foamListTimes -processor | tail -n 1)



# get write interval from controlDict

sS="writeInterval"

wI=$(grep -i $sS system/controlDict)

# trim

wI=${wI//;/}

wI=${wI// /}

wI=${wI#$sS}

writeInterval=$wI



# create the directory for the script

mkdir Animation



# first argument is number of time steps, second argument is time step

pvbatch --use-offscreen-rendering batchExport.py $timeSteps $writeInterval

However, there are still two issues with it:

At the end of the code's execution, I get the error message

Code:

Inconsistency detected by ld.so: dl-close.c: 811: _dl_close: Assertion `map->l_init_called' failed!

Why is that and how can I get rid of it? The code still executes, but I'd like to know where the error is from.
This is the more important issue: At a writeInterval of 0.5, the screenshots for a time period of 2s (four screenshots) always look completely the same. For example, the first four screenshots, at 0s, 0.5s, 1.0s and 1.5s all show the same result. Then there's a change between 1.5 and 2s, but then no change until and including 3.5s.
Any ideas why that is? And maybe even how to fix it?

I searched online for both issues, but to no avail. Any feedback would be greatly appreciated.

The OpenFOAM version on the remote server is 2.4.0, so the ParaView version should be 4.1.0.

Lennart