NumericalAlgorithm/ChangeP1toP2Mesh.m at master · guihunkun/NumericalAlgorithm · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
function [p,t] = ChangeP1toP2Mesh(p,t)
%
%  Input:  p: nodes
%          t: index of node
%  Each triangle is described by three points.

%  Output: p: nodes
%          t: index of node
%  Each triangle is described by six points.
%
%    y
%    |
%    |
%    |
%    3
%    |\
%    |  \
%    6    \5
%    |      \
%    |________\ ________x
%    1    4    2
%
%  ex:
%  p = [0,0; 1,0; 0,1]';
%  t = [1;2;3;1];
%  p = [0,0; 1,0; 0,1; 1/2,0; 1/2,1/2; 0,1/2];
%  t = [1;2;3;4;5;6];
%

        np=size(p,2);        % number of nodes
        edges=Tri2Edge(p,t); % get element edge numbers
        edges=edges+np;      % change edges to new nodes
        i=t(1,:); j=t(2,:); k=t(3,:);
        e=edges(:,1);
        p(1,e)=0.5*(p(1,j)+p(1,k));
        p(2,e)=0.5*(p(2,j)+p(2,k));
        e=edges(:,2);
        p(1,e)=0.5*(p(1,i)+p(1,k));
        p(2,e)=0.5*(p(2,i)+p(2,k));
        e=edges(:,3);
        % edge node coordinates
        p(1,e)=0.5*(p(1,i)+p(1,j));
        p(2,e)=0.5*(p(2,i)+p(2,j));
        % t(7,:)=t(4,:); % move subdomain info, resize t
        t(4:6,:)=edges'; % insert edge nodes into t
        tt = t;
        t(4,:) = tt(6,:);
        t(5,:) = tt(4,:);
        t(6,:) = tt(5,:);
end