View source for Visualization of 2D and 3D datasets with ParaView

== Scientific visualization with ParaView ==

For visualization of 2D and 3D data we highly recommend [http://www.paraview.org ParaView], an open-source, multi-platform, general-purpose visualization and analysis application. It can visualize data both interactively and via Python scripting, supports a large variety of input formats, can deal with structured and unstructured meshes in 2D and 3D, and can scale to handle very large datasets (gigabytes to terabytes).

We have ParaView installed on [[Visualization Workstations]], however, to learn ParaView, we suggest that you first install it on your dekstop/notebook and start playing there, and then you can move to our larger machines. ParaView is available as a free [http://www.paraview.org/paraview/resources/software.html binary download] for all major platforms (Linux, Windows, Mac).

== Importing data into ParaView ==

There are many ways to import data into ParaView. Some of them -- raw data, VTK formats (both legacy and XML), XMDF -- are covered in the slides from the 2010 summer school below. However, the easiest solution is probably to store your dataset using [https://www.sharcnet.ca/my/software/show/18 NetCDF] which ParaView can read natively.

[http://razoumov.sharcnet.ca/paraview/writeNetCDF.f90 This sample f90 program]
(and [http://razoumov.sharcnet.ca/paraview/writeNetCDF.c the same program in C])
writes a 30^3 volume with a doughnut shape at the centre in NetCDF. You can compile and run it on a cluster where NetCDF is installed:

 ### f90 example ###
 module load netcdf/intel/4.1.2
 ifort writeNetCDF.f90 -o writeNetCDF $CPPFLAGS $LDFLAGS -lnetcdff -lnetcdf
 ./writeNetCDF

 ### C example ###
 module load netcdf/intel/4.1.2
 icc writeNetCDF.c -o writeNetCDF $CPPFLAGS $LDFLAGS -lnetcdf
 ./writeNetCDF

This will create a ~100kB file ''volume.nc''. Copy it to your local machine, where you have ParaView installed. From Paraview, navigate to the file (File - Open) and then press Apply in the '''Object Inspector''' to load the file. Highlight ''volume.nc'' in the '''Pipeline Browser''' to make it visible, select Volume in the drop-down menu, click on Edit Color Map icon, then on Choose Preset and select the desired colour map. In the main visualization window on the right you should be able to see volume rendering similar to the one shown below. The 3D object is fully interactive: you can rotate and move it, as well as zoom in/out, dragging it with one of the three mouse buttons. Play with the colour map; you will discover that the brightness in the colour map is tied to the data value, so that you can highlight the central object or the surroundings.

[[File:Volume1.png|700px]]

== ParaView slides ==

* [[Media:Ss2010_vt.pdf|Using visualization tools on SHARCNET]] (slides from Summer School 2010, 53 pages, pdf format) 
* [[Media:Parallel_Visualization_with_Paraview.pdf|Parallel Visualization with ParaView]] (introductory slides, 26 pages, pdf format)

== Dataset limitations ==

The major constraint on the size of the dataset that you can explore with ParaView is the amount of physical memory on a machine. On a typical desktop with 2 GB memory you can work interactively with datasets up to ~500^3. Some of our visualization workstations have 48GB memory and will let you visualize datasets up to ~2000^3 (single variable in single precision), or smaller datasets with multiple variables, or process these datasets with more CPU- and memory-intensive filters.

[[Category:Visualization]]