Establish line sink as default driving function for 2D WFS focused so…

…urce

SFS_monochromatic/driving_functions_mono/driving_function_mono_wfs_fs.m

@@ -16,7 +16,8 @@
 %
 % DRIVING_FUNCTION_MONO_WFS_FS(x0,xs,f,src,conf) returns WFS driving signals
 % for the given secondary sources, the virtual focused source position and the
-% frequency f.
+% frequency f. For 3D and 2.5D the default behavior is to use a focused point
+% source as source model, for 2D a focused line source is used instead.
 %
 % See also: driving_function_mono_wfs, driving_function_imp_wfs_ps
 
@@ -71,14 +72,14 @@
 end
 
 
-%% ===== Configuration ==================================================
+%% ===== Configuration ===================================================
 xref = conf.xref;
 c = conf.c;
 dimension = conf.dimension;
 driving_functions = conf.driving_functions;
 
 
-%% ===== Computation ====================================================
+%% ===== Computation =====================================================
 % Calculate the driving function in time-frequency domain
 
 % Frequency
@@ -89,6 +90,11 @@
 
  % === 2- or 3-Dimensional ============================================
 
+ % For 2D the default focussed source should be a line sink
+ if strcmp('2D',dimension) && strcmp('default',driving_functions)
+ driving_functions = 'line_sink';
+ end
+
  switch driving_functions
  case 'default'
  % --- SFS Toolbox ------------------------------------------------
@@ -163,7 +169,6 @@
  'for a focused source.'],upper(mfilename),driving_functions);
  end
 
-
 elseif strcmp('2.5D',dimension)
 
  % === 2.5-Dimensional ================================================

SFS_time_domain/driving_functions_imp/driving_function_imp_wfs_fs.m

@@ -81,6 +81,11 @@
 
  % === 2- or 3-Dimensional ============================================
 
+ % For 2D the default focussed source should be a line sink
+ if strcmp('2D',dimension) && strcmp('default',driving_functions)
+ driving_functions = 'line_sink';
+ end
+
  switch driving_functions
  case 'default'
  % --- SFS Toolbox ------------------------------------------------
@@ -98,6 +103,21 @@
  delay = -1./c .* r;
  weight = 1./(2.*pi) .* vector_product(xs-x0,nx0,2) ./ r.^2;
  %
+ case 'line_sink'
+ % d using a focused line source as source model
+ % ___
+ % | 1 (x0-xs) nx0
+ % d(x0,t) = h(t) * _ |--- ------------- delta(t+|x0-xs|/c)
+ % \|2pi |x0-xs|^(3/2)
+ %
+ % See http:https://sfstoolbox.org/#equation-d.wfs.fs.ls
+ %
+ % r = |x0-xs|
+ r = vector_norm(x0-xs,2);
+ % Delay and amplitude weight
+ delay = -1./c .* r;
+ weight = 1./(2.*pi) .* vector_product(x0-xs,nx0,2) ./ r.^(3./2);
+ %
  case 'legacy'
  % --- Old SFS Toolbox default ------------------------------------
  % d using a focused point source as source model