mergemesh

 [newnode,newelem]=mergemesh(node,elem,varargin)

 concatenate two or more tetrahedral meshes or triangular surfaces
 
 author: Qianqian Fang <fangq at nmr.mgh.harvard.edu>

 input: 
      node: node coordinates, dimension (nn,3)
      elem: tetrahedral element or triangle surface (nn,3) to (nn,5)

 output:
      newnode: the node coordinates after merging, dimension (nn,3)
      newelem: tetrahedral element or surfaces after merging (nn,4) or (nhn,5)

 note: you can call meshcheckrepair for the output newnode and
 newelem to remove the duplicated nodes or elements. mergemesh does
 detect self-intersecting elements when merging; to remove self-intersecting
 elements, you need to use mergesurf().

 example:

   [node1,face1,elem1]=meshabox([0 0 0],[10 10 10],1,1);
   [node2,face2,elem2]=meshasphere([5 5 13.1],3,0.3,3);
   [newnode,newelem]=mergemesh(node1,elem1,node2,elem2);
   plotmesh(newnode,newelem);
   figure;
   [newnode,newface]=mergemesh(node1,face1,node2,face2);
   plotmesh(newnode,newface,'x>5');

 -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)

0001 function [newnode,newelem]=mergemesh(node,elem,varargin)
0002 %
0003 % [newnode,newelem]=mergemesh(node,elem,varargin)
0004 %
0005 % concatenate two or more tetrahedral meshes or triangular surfaces
0006 %
0007 % author: Qianqian Fang <fangq at nmr.mgh.harvard.edu>
0008 %
0009 % input:
0010 %      node: node coordinates, dimension (nn,3)
0011 %      elem: tetrahedral element or triangle surface (nn,3) to (nn,5)
0012 %
0013 % output:
0014 %      newnode: the node coordinates after merging, dimension (nn,3)
0015 %      newelem: tetrahedral element or surfaces after merging (nn,4) or (nhn,5)
0016 %
0017 % note: you can call meshcheckrepair for the output newnode and
0018 % newelem to remove the duplicated nodes or elements. mergemesh does
0019 % detect self-intersecting elements when merging; to remove self-intersecting
0020 % elements, you need to use mergesurf().
0021 %
0022 % example:
0023 %
0024 %   [node1,face1,elem1]=meshabox([0 0 0],[10 10 10],1,1);
0025 %   [node2,face2,elem2]=meshasphere([5 5 13.1],3,0.3,3);
0026 %   [newnode,newelem]=mergemesh(node1,elem1,node2,elem2);
0027 %   plotmesh(newnode,newelem);
0028 %   figure;
0029 %   [newnode,newface]=mergemesh(node1,face1,node2,face2);
0030 %   plotmesh(newnode,newface,'x>5');
0031 %
0032 % -- this function is part of iso2mesh toolbox (http://iso2mesh.sf.net)
0033 %
0034 
0035 len=length(varargin);
0036 newnode=node;
0037 newelem=elem;
0038 if(len>0 & mod(len,2)~=0)
0039    error('you must give node and element in pairs');
0040 end
0041 
0042 X=mesheuler(newelem);
0043 
0044 if(size(newelem,2)==4)
0045    if(X>=0)
0046       newelem(:,end+1)=1;
0047    end
0048 end
0049 if(size(newelem,2)==3)
0050    newelem(:,end+1)=1;
0051 end
0052 for i=1:2:len
0053    no=varargin{i};
0054    el=varargin{i+1};
0055    baseno=size(newnode,1);
0056    if(size(no,2)~=size(newnode,2))
0057         error('input node arrays have inconsistent columns');
0058    end
0059    if(size(el,2)==5 | size(el,2)==4)
0060         el(:,1:4)=el(:,1:4)+baseno;
0061     if(size(el,2)==4 & X>=0)
0062        el(:,5)=1+(i+1)/2;
0063     end
0064        newnode=[newnode;no];
0065     newelem=[newelem;el];
0066    elseif(size(el,2)==3 & size(newelem,2)==4)
0067         el(:,1:3)=el(:,1:3)+baseno;
0068     if(size(el,2)==3)
0069        el(:,4)=1+(i+1)/2;
0070     end
0071        newnode=[newnode;no];
0072     newelem=[newelem;el];
0073    else
0074         error('input element arrays have inconsistent columns');
0075    end
0076 end