% **************************************************************
% lbem2_on : Sets up diagonal of matrices for BEMLAP
% **************************************************************
% BEM-LAP-MAT project
% Matlab/Freemat codes
% Copyright 2008- Stephen Kirkup
% John Tyndall Nuclear Research Institute
% School of Computing Engineering and Physical Sciences
% University of Central Lancashire - www.uclan.ac.uk 
% Westlakes Campus
% Samuel Lindow Building
% West Lakes Science and Technology Park
% Whitehaven
% Cumbria CA24 3JY
% United Kingdom
% smkirkup@uclan.ac.uk
%
% This open source code can be found at
% boundary-element-method.com/freematlab/lbem2_on.m
%
%  Issued under the GNU General Public License 2007, see gpl.txt
%
%  Part of the the author's open source BEM packages. 
%  All codes and manuals can be downloaded from 
%  www.boundary-element-method.com
%
% **************************************************************

% function [L,M,Mt,N] =lbem2(n,vertpts,elemvert,p_on,needL,needM,needMt,needN)
% Sets up the matrices required in the boundary element method
%  for a boundary made up of n elements. vertpts lists the coordinates
%  of the edges of the elements and elemvert lists the pairs of vertices
%  that define each element.needL,needM,needMt,needN indicate which matrices
%  are needed by being set to true.


function [L,M,Mt,N] =lbem2_on(n,vertpts,elemvert,needL,needM,needMt,needN)

  [qa,qb]=vertices(n,vertpts,elemvert);

  p=(qa+qb)/2;
  
  qbma=qb-qa;
  
  for(i=1:n)
    qlen(i)=norm(qbma(i,:));
  end

  for (i=1:n)
    normp(i,1)=-qbma(i,2)/qlen(i);
    normp(i,2)=qbma(i,1)/qlen(i);
  end
   
  [L,M,Mt,N] =lbem2(n,p,normp,n,vertpts,elemvert,true,needL,needM,needMt,needN);