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WKB initial field
Use internal field from WKB approximation as an input for the iterative
solver. Should be effective for index-matching particles.
Original issue reported on code.google.com by yurkin on 24 Dec 2008 at 7:56
This should be implemented (in some form) by the end of 2010.
Original comment by yurkin on 22 Mar 2010 at 6:19
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Original comment by yurkin on 22 Mar 2010 at 6:23
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First implementation of the WKB incident field is done by r981, but it has a
major limitation. It only works for the default incident direction (along the
z-axis in the particle reference frame).
Preliminary tests that using this option leads to some acceleration for
index-matching particles (up to 20% decrease in number of iterations).
r981 - 9ca930472d826ea4081a6001339748c7f2111186
Original comment by yurkin on 29 Sep 2010 at 6:15
Original comment by yurkin on 2 Dec 2010 at 4:40
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Original comment by yurkin on 22 Apr 2011 at 2:39
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Currently WKB does not work at all in sparse mode. However, that is probably
fine, since it is not expected to be a good approximation for sparse objects
(where no large homogeneous parts are present).
Original comment by yurkin on 4 Feb 2013 at 5:32
Original comment by yurkin on 4 Feb 2013 at 5:34
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Specific formulae to transform from WKB field to starting vector were slightly
changed (improved) by r1223.
r1223 - c8154735ef2a3957da176acdcfe28d7ec55d1d6a
Original comment by yurkin on 4 May 2013 at 5:17
It should also be made operational together with -surf
Original comment by yurkin on 25 Sep 2013 at 10:21
It happens that there are certain ambiguity in definition of the WKB. In
particular, there may be additional multiplicative factor in the definition of
the internal field, either 2/(m+1) or 1/sqrt(m). See, e.g.,
Klett JD, Sutherland RA. Approximate methods for modeling the scattering
properties of nonspherical particles: evaluation of the
Wentzel-Kramers-Brillouin method. Appl. Opt. 1992;31:373–386.
http://dx.doi.org/10.1364/AO.31.000373
Should not be imprortant in the limit m->1, but seems worth experimenting with.
Original comment by yurkin on 11 Apr 2015 at 4:30
