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# source_tess

## (Toolbox/source_tess.m in BrainStorm 2.0 (Alpha))

### Function Synopsis

    [L,xl,yl,zl,geol,tri_num] = ...

### Help Text

    SOURCE_TESS - generate variable grid of possible source locations
     function [L,xl,yl,zl,geol,tri_num] = ...
         source_tess(sensor_r,source_maxr,source_minr,coverage,Factor);
     Given the scalar radius to the sensors sensor_r,
      the maximum scalar radius to the sources source_rmax,
      the minimum scalar radius to the sources source_rmin,
      then generate possible dipole source locations L in the upper hemisphere.

     tri_num is the number of triangles per ring.  A zero indicates the
     start of a new surface.  ctri_sum = cumsum(tri_sum); nd = find(~tri_num);
     ctri_sum(nd) gives the number of triangles per surface.
     Coverage is from tesselate, 'half','full',or radian from z-axis
     Optional Factor is the fraction considered significant, default 0.1;

### Cross-Reference Information

This function calls

    tesselate                          C:\BrainStorm_2001\Toolbox\tesselate.m

### Listing of function C:\BrainStorm_2001\Toolbox\source_tess.m

    function [L,xl,yl,zl,geol,tri_num] = ...
        source_tess(sensor_r,source_maxr,source_minr,coverage,Factor);
    %SOURCE_TESS - generate variable grid of possible source locations
    % function [L,xl,yl,zl,geol,tri_num] = ...
    %     source_tess(sensor_r,source_maxr,source_minr,coverage,Factor);
    % Given the scalar radius to the sensors sensor_r,
    %  the maximum scalar radius to the sources source_rmax,
    %  the minimum scalar radius to the sources source_rmin,
    %  then generate possible dipole source locations L in the upper hemisphere.
    %
    % tri_num is the number of triangles per ring.  A zero indicates the
    % start of a new surface.  ctri_sum = cumsum(tri_sum); nd = find(~tri_num);
    % ctri_sum(nd) gives the number of triangles per surface.
    % Coverage is from tesselate, 'half','full',or radian from z-axis
    % Optional Factor is the fraction considered significant, default 0.1;

    %<autobegin> ---------------------- 26-May-2004 11:34:31 -----------------------
    % --------- Automatically Generated Comments Block Using AUTO_COMMENTS ---------
    %
    % CATEGORY: Forward Modeling
    %
    % Alphabetical list of external functions (non-Matlab):
    %   toolbox\tesselate.m
    %
    % At Check-in: $Author: Mosher $  $Revision: 12 $  $Date: 5/26/04 10:02a $
    %
    % This software is part of BrainStorm Toolbox Version 2.0 (Alpha) 24-May-2004
    %
    % Principal Investigators and Developers:
    % ** Richard M. Leahy, PhD, Signal & Image Processing Institute,
    %    University of Southern California, Los Angeles, CA
    % ** John C. Mosher, PhD, Biophysics Group,
    %    Los Alamos National Laboratory, Los Alamos, NM
    % ** Sylvain Baillet, PhD, Cognitive Neuroscience & Brain Imaging Laboratory,
    %    CNRS, Hopital de la Salpetriere, Paris, France
    %
    % See BrainStorm website at http://neuroimage.usc.edu for further information.
    %
    % Copyright (c) 2004 BrainStorm by the University of Southern California
    % This software distributed  under the terms of the GNU General Public License
    % as published by the Free Software Foundation. Further details on the GPL
    % license can be found at http://www.gnu.org/copyleft/gpl.html .
    %
    % FOR RESEARCH PURPOSES ONLY. THE SOFTWARE IS PROVIDED "AS IS," AND THE
    % UNIVERSITY OF SOUTHERN CALIFORNIA AND ITS COLLABORATORS DO NOT MAKE ANY
    % WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF
    % MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, NOR DO THEY ASSUME ANY
    % LIABILITY OR RESPONSIBILITY FOR THE USE OF THIS SOFTWARE.
    %<autoend> ------------------------ 26-May-2004 11:34:31 -----------------------

    % John C. Mosher, Ph.D.
    % See Copyright.m file for information
    % $Date: 5/26/04 10:02a $ $Revision: 12 $
    %
    % February 8, 1995 author
    % JCM 2/27/95 cleanup from test version to production
    % JCM 4/4/95 generate fill3 surfaces, derived from source_grid

    % uses: tesselate

    if(exist('Factor') ~= 1),    % user gave no Factor
      Factor = 0.1;         % what Factor is considered insignificant
    end

      next_r = source_maxr;     % initialize
      L = [];            % source locations
      xl = [];            % vertices for x
      yl = [];            % y
      zl = [];            % z
      geol = [];            % geometry matrix
      tri_num = [];            % number of triangles
      isurfaces = 0;         % number of surfaces used

      while(next_r > source_minr),     % for appropriate spherical surfaces
        isurfaces = isurfaces + 1;
        min_d = sensor_r - next_r;     % min distance to between source and sensor
        spacing = 2*min_d*Factor; % spacing between sensors
        theta_inc = acos(1 - 0.5*(spacing/next_r)^2); % sensor increment
        if(next_r > spacing),
          [jkx,jky,jkz,jkL,jkg,jkt] = tesselate(next_r,spacing,coverage);
          % Rn = sensor_ring(next_r,theta_inc,ceil((pi/2)/theta_inc));
          xl = [xl jkx];
          yl = [yl jky];
          zl = [zl jkz];
          geol = [geol jkg+size(L,1)];
          L = [L;jkL];         % add these source locations
          tri_num = [tri_num jkt];
        end
        next_r = next_r - spacing;
        tri_num = [tri_num 0]; % tag the start of a new surface
      end

    return

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