= Animated movie of neuroscience brain data with ParaView
[[PageOutline]]

== Background
At FZJ, the institute for [http://www.fz-juelich.de/inm/inm-1/EN/Home/home_node.html structural and functional organisation of the brain (INM-1)] develops a 3-D model of the human brain which considers cortical architecture, connectivity, genetics and function. The INM-1 research group [http://www.fz-juelich.de/inm/inm-1/EN/Forschung/Fibre%20Architecture/Fibre%20Architecture_node.html Fiber Architecture] develops techniques to reconstruct the three-dimensional nerve fiber architecture in mouse, rat, monkey, and human brains at microscopic resolution. As a key technology, the neuroimaging technique Three-dimensional Polarized Light Imaging (3D-PLI) is used. To determine the spatial orientations of the nerve fibers, a fixated and frozen postmortem brain is cut with a cryotome into histological sections (≤ 70 µm). Every slice is then scanned by high resolution microscopes.

== Data
The datset used in this visualisation scenario consists of 234 slices of gridsize 31076x28721, resulting in a rectilinear uniform grid of size 31076x28721x234, ~200 GB memory usage in total. The data was stored as raw binary unsigned char data, one file for each slice.

== Conversion to HDF5
Because !ParaView has a very decent XDMF/HDF5 reader, we decided to convert the raw data to hdf5 first.
This was done using a Python script. Before Python can be used on our JURECA cluster, the necessary modules have to be loaded first:
{{{
module load GCC/5.4.0
module load ParaStationMPI/5.1.5-1
module load h5py/2.6.0-Python-2.7.12
module load HDF5/1.8.17
}}}

In the Python-script, the directory containing the 234 slice files is scanned for the filenames. Every file is opened and the raw content is read into a numpy array. This numpy array is written into a hdf5 file, which was created first. 

{{{
#!python
import sys
import h5py # http://www.h5py.org/
import numpy as np
import glob

dir = "/homeb/zam/zilken/JURECA/projekte/hdf5_inm_converter/Vervet_Sehrinde_rightHem_direction/data"
hdf5Filename="/homeb/zam/zilken/JURECA/projekte/hdf5_inm_converter/Vervet_Sehrinde_rightHem_direction/data/Vervet_Sehrinde.h5"

# grid-size of one slice
numX = 28721
numY = 31076

#scan directory for filenames
files = glob.glob(dir + "/*.raw")
numSlices = len(files) # actually 234 slices for this specific dataset

# create hdf5 file
fout = h5py.File(hdf5Filename, 'w')
# create a dataset in the hdf5 file of type unsigned char = uint8
dset = fout.create_dataset("PLI", (numSlices, numX, numY), dtype=np.uint8)

i = 0
for rawFilename in sorted(files):
   print "processing " + rawFilename
   sys.stdout.flush()

   # open each raw file
   fin = open(rawFilename, "rb")
   # and read the content
   v = np.fromfile(fin, dtype=np.uint8, count=numX*numY)
   fin.close()
   v = v.reshape(1, numX, numY)
   # store the data in the hdf5 file at the right place
   dset[i, : , :]=v


print "success"
fout.close()

}}}

== Creating XDMF Files