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1. Load the mesh and particles via the folder icon in the SLAC Toolbar.
2. Zoom to where the particles are, and make sure you can see them.
   1. It may be necessary to turn off the mesh surface or switch to wireframe, because the mesh rendered as a surface will usually hide the particles inside.
   2. It may be necessary to advance beyond the first timestep to see particles because in some simulations, particles are not created until after the first timestep.
   3.  
3. Apply the particle pathline filter
   1. Make sure you have selected the particle data in the Pipeline Browser, and have them set to visible (small eye icon toggls this).
   2. Create the filter ("Filters -> Alphabetical -> Particle Pathlines")
   3. Adjust parameters
      1. "Mask Points" will only use a subset of the total particles to increase performance.  A value of 1 means show every particle, 2 means every other particle, 10 means every 10th particle, and so on.  Use 1 unless you need otherwise.
      2. Max Track Length  and Max Step Distance need to be adjusted to taste.  Accept the default for now.
      3. Hit "Apply".  This will create two new pipeline objects "Pathlines" and "Particles". If your particles disapper here, possibly your Mask Points is too large (so try a value of 1).
4. Handle particle heads and tails.
   1. For particle heads, It often helps to show them as glyphs (spheres or cones, for example)
      1. Select the newly created "Particles" source in the Pipeline Browser.
      2. "Filters -> Alphabetical -> Glyph"
         1. "Glypth Type": Sphere
         2. "Scale Mode": Off (to keep all particles the same size)
         3. "Mask points" is to reduce the number of particles that are shown to a subset.  Turn this off.
         4. "Random Mode" doesn't matter if "Mask Points" is unchecked.  But if you are masking, random mode choses a random subset to hopefully chose a distributed set of particles rather than just the first n, which may all be bunched together.
         5. "Orient" is not necessary for sphere glyphs, but would make sense for cone glyphs.
         6. Finer Theta/Phi resolution well keep the spheres looking more spherical, but takes longer to render, and may not be needed if the camera never gets very close to the particles.
         7. Hit "Apply".
         8. Adjust the "Radius" according to your taste.
         9. Select the coloring you prefer.  "EmissionType" is default, but "Momentum" or "Solid Color" can be useful as well.  You may need to adjust the field scaling and color map via the "Edit Color Map" button.
         10. If "Particles" is still visible you may see small dots together with the sphere glyphs.  Remember to turn off "Particles" visibility so that only the sphere glyphs are seen.  Though often it is helpful to leave them on temporarily while setting up glyphs just so you have something to see and provide context.
      3. Head Troubleshooting:
         1. I don't see any particles.
            1. Does your dataset have any particles in the first timestep?  It may be necessary to go to a later timestep.
         2. My particles have crazy different sizes.
            1. Make sure "Scale Mode" is set to "off".
         3. My particles have crazy (but consistent sizes).
            1. Adjust "Radius" accordingly.  Often the default radius is much too large.
         4. My particles have crazy colors.
            1. Check that you're mapping the right thing onto them: Momentum or Emission Type, or Solid Color
         5. My particles have reasonable colors, but too much (or not enough) red.
            1. When you hit the "Rescale to Data Range" button by the "Edit Colormap" button, it's rescaling based on the *current* timestep.  So, for multipacting, for example, momentum is usually highest just before impact.  So move forward/backward in time to just before the impact and "Rescale to Data Range" for that timestep.     For more red, "Rescale to Data Range even earlier.
         6. I see (probably) white dots on most of my sphere glyphs.
            1. Turn off visibility for you particle data, and for "Particles" in your pipline browser.  The corresponding glyph should be left visible, however.
   2. For particle trails, it is often helpful to use apply a tube filter.  This takes longer to render, but shows depth relationships more clearly, and gives the particles position history.
      1. Select "Pathlines" in the Pipeline Browser.
      2. "Filters -> Alphabetical -> Tube"
         1. The defaults are not bad.
         2. But "Number of sides" usually needs to be increased to at least 8 for tubes to have better shading
         3. Adjust "Radius" to taste, and to coordinate well with the sphere glyphs for the particles.
            1. Too thick will result in a lot of occlusion, meaning much of your data will be hidden in the image.
            2. Too thin doesn't leave room for shading, and prevents good depth discernment.
            3. A tail that appears to be half as wide as the particle sphere usually works reasonably well.
         4. Map something appropriate to the tail color
            1. "Solid Color"  works well for lighter colors (white, yellow, for example) for clearer shading and depth discernment.  Solid colors also won't compete with other colors so that visual information is more clearly presented.
            2. "Momentum" can be meaningful, though can also result in a lot of visual clutter.
            3. Using a white trail and mapping momentum (or emission type) to the sphere instead, is usually more clear.
         5. Play the animation (using the play button in the VCR toolbar) to get a sense of how long your trails should be whether they are too thick/thin, and whether things are too cluttered.  Adjust the corresponding parameters accordingly.
      3. Tail Troubleshooting
         1. I don't see any trails.
            1. The trails are constructed from the results of playing consecutive timesteps.  So you'll need to start at a time when you have particles, and play forward a few steps so that the trails can grow.  If you step backward in time, or forward by more than one step, the Particle Pathline filter gets confused.
5. General Troubleshooting
   1. Once a particle bounces off a wall, sometimes the portion of the tail from before the bounce disappears.
      1. This is a known issue.  There is presently no workaround.
   2. I'm working on trial runs of generating a movie.  But rendering is very slow.
      1. keep the resolution (number of sides) for the spheres and tubes as low as still looks good.
      2. temporarily disable the spheres/tubes, and mapping the same quantities on the points/lines.  Points and lines can have their sizes/widths adjusted (within limits), and are much faster to draw.

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