Visit-tutorial-mir

Resources

Slides:

Data:

Set up a Filled Boundary and Mesh plot with PLIC

  • open torus_mat.silo -- this is supposed to be a thin green shell surrounded by two other materials
  • open the Controls -> Material Options dialog
  • choose PLIC from the Algorithm list
  • hit Apply
    • note the warning about only applying to new plots due to our caching of potentially expensive reconstructions.... no problem, we can just hit ReOpen to force a recalculation
  • back to main window, create a Filled Boundary Plot of the variable Material, and hit Draw
    • add a Mesh plot, and zoom in a bit
    • note that some cells have the material ordering wrong, and some have guessed slopes incorrectly
    • zoom waaay in to the upper-left portion of the torus, and note that even where it's done everything correctly, it's still discontinuous

Change to the Discrete algorithm, show with and without annealing

  • in Material Options, choose Discrete from the list
    • then set the annealing time to zero, hit Apply, and ReOpen
    • note in the main window the random starting conditions for mixed cells
    • increase the annealing time to 1 second, hit Apply, then ReOpen
    • note it's much better, though it may not get the thin shell correct

Change to Isovolume, note the smoothness and the holes

  • in Material Options, choose Isovolume from the list, hit Apply, then ReOpen
    • note that it hasn't reconstructed the green shell -- that's actually one of those 3-material holes, though the results are nice and smooth

Change to Equi-T, note the missing shell and the wobbles

  • in Material Options, choose Equi-T (Tetrahedral clipping) from the list, hit Apply, then ReOpen
    • note that it's also missing the green material, so accuracy still isn't good
    • zoom in to upper-right section of torus, and note the wobbles from the poor clipping
    • stay zoomed in for now....

Change to Equi-Z, note the lack of wobbles, but still missing shell

  • in Material Options, choose Equi-Z (improved finite element Zoo clipping) from the list, hit Apply, then ReOpen
    • note the wobbles are gone, but we're still missing the green material
    • this calls for iteration!

Turn on iteration, tune the parameters

  • so in Material Options, click the Iteration checkbox; leave the iterations and convergence at their default (i.e. 5 iterations, 0.4 convergence); hit Apply, then ReOpen
    • note we picked up some of the green shell, but it's not looking all that great
    • let's tune the iteration parameters:
      • lower the convergence factor to 0.3 (which means change less on each iteration; note that 0.4 is about as high as I'd recommend you go, as the higher the value, the less likely it will converge)
      • and to compensate, increase the number of iterations to 10
      • (aside: a few more iterations would still have worked well with a 0.4 C.F., but if you look at the results from 4, 5, 6, 7 iterations, you will see some oscillation around the correct answer, so a slightly lower C.F. really is better here)

Show material selection on Pseudocolor and Mesh plots

  • Finally, note that material selection can be used for all sorts of analysis features, not just seeing your materials:
    • delete the Filled Boundary Plot
    • add a Pseudocolor plot of U
    • go to Controls -> Subset, or click the matching icon next to the plot
    • turn off all the materials except "2 B", and hit Apply
    • note that the plot and all queries will now operate on the selected data