function newval=meshremap(fromval,elemid,elembary,toelem,nodeto)
%
% newval=meshremap(fromval,elemid,elembary,toelem,nodeto)
%
% Redistribute nodal values from the source mesh to the target mesh so that
% the sum of each property on each mesh is the same
%
% author: Qianqian Fang (q.fang at neu.edu)
%
% input:
% fromval: values defined at the source mesh nodes, the row or column
% number must be the same as the source mesh node number, which
% is the same as the elemid length
% elemid: the IDs of the target mesh element that encloses the nodes of
% the source mesh nodes; a vector of length of src mesh node
% count; elemid and elembary can be generated by calling
%
% [elemid,elembary]=tsearchn(node_target, elem_target, node_src);
%
% note that the mapping here is inverse to that in meshinterp()
%
% elembary: the bary-centric coordinates of each source mesh nodes
% within the target mesh elements, sum of each row is 1, expect
% 3 or 4 columns (or can be N-D)
% toelem: the element list of the target mesh
% nodeto: the total number of target mesh nodes
%
%
% output:
% newval: a 2D array with rows equal to the target mesh nodes (nodeto),
% and columns equals to the value numbers defined at each source
% mesh node
% example:
%
% [n1,f1,e1]=meshabox([0 0 0],[10 20 5],1); % src mesh
% [n2,f2,e2]=meshabox([0 0 0],[10 20 5],2); % target mesh
% [id, ww]=tsearchn(n2,e2,n1); % project src to target mesh
% value_src=n1(:,[2 3 1]); % create dummy values at src mesh
% newval=meshremap(value_src,id,ww,e2,size(n2,1)); % map to target
%
% -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)
%
if(size(fromval,1)==1)
fromval=fromval(:);
end
if(size(fromval,2)==length(elemid))
fromval=fromval.';
end
newval=zeros(nodeto,size(fromval,2));
idx=~isnan(elemid);
fromval=fromval(idx,:);
elembary=elembary(idx,:);
idx=elemid(idx);
nodeval=repmat(fromval,1,1,size(elembary,2)).*repmat(permute(elembary,[1,3,2]),1,size(fromval,2),1);
for i=1:size(elembary,2)
[ix,iy]=meshgrid(toelem(idx,i),1:size(fromval,2));
nval=nodeval(:,:,i).';
newval=newval + accumarray([ix(:),iy(:)],nval(:), size(newval));
end
