View source for HowTo use particle tracer in paraFoam

The '''particle tracer''' filter in paraview creates massless particle tracking with pathlines that animates over time without lagrangian data. 

[[File:ParaviewParticleTracerExample.png|right|500px|Visualization pipeline]]
[[File:ParticlePathlinesScreenshot.png|right|500px|Visualization pipeline with Temporal Interpolator]]

==Example: icoFoam/cavity==

We will use the ''$FOAM_TUTORIALS/incompressible/icoFoam/cavity'' tutorial case to exemplify the pipeline.

==Visualization pipeline for Particle Tracer filter==

# Load your velocity fields (U) in paraview.
#* If you have a large dataset you should apply the '''Temporal Interpolator''' filter in order to decrease the time data, and so decrease the chance of segmentation fault. This filter can also be used to interpolate saved time steps that are typically too sparse to create a smooth particle tracking animation by themselves.
# Generate the seed points from a source object (Point Source, Line, Plane, etc.)  in the '''Sources''' menu. It must intersect your mesh and you can regulate the number of seed points (resolution) on your Source object.
# Apply the '''Particle Tracer''' filter taking your data as ''input'' and your source object (Point Source, Line, Plane, etc.) as ''source''. The option '''Force Reinjection Every NSteps''' gives the injection rate per time step (0: injects only at the beginning; 1: injects every time step).


===Optional===
After the passive particles were created, you can improve the visualization of them by:

* '''Glyph:''' you can make the particles larger using "Glyph Type=Sphere" and "scale mode=off". Set the scale according to the particle size you want to visualize.

* '''Temporal Particles to Path:''' with this filter you can visualize the path "tails" of each of your particles, like comets. The particle path is integrated by a number of time steps defined by  Max Track Length (2 for 1 time step). "Id Channel Array=ParticleId". 
** ''Input'': Particle Tracer Filter. 
** ''Output'': Pathlines AND Particles.
*** ''Hints'': You can Glyph the Particles and Tube the Pathlines, so they will look better. You can make moving vectors if you glyph the particles as cones. The cones would be the vector heads.

==References==

This tutorial is based on [http://www.cfd-online.com/Forums/openfoam-paraview/82036-do-particle-tracking-paraview.html#post283475| this post] on cfd-online.com.

[[Category:Tutorials]]
[[Category:Post-processing utilities]]
[[Category:Lagrangian]]
[[Category:ParaFoam]]