是一段关于三角形网格数据前处理的matlab程序 实在看不懂 有人能翻译一下吗 就只要告诉我输出了什么结果就可以了 p是n2的表格 代表n个节点的x，y坐标 t是m3的表格 代表构成每一个网格的节点标号 类似mike的mesh文件
function data = data_structure(p,t)
% Build data structures used in the solver.
%
% This function builds the mesh parameters and connectivity that will be
% used in tvd_rk2.m. Building this initially saves HEAPS of CPU time later
% in tvd_rk2.m, but of course, my meshes are fixed for the integration.
%
% Darren Engwirda - 2005-2006.
%
% Naver2d is Copyright (C) 2005-2006 Darren Engwirda. See "copyright.m" for
% full details.
w = waitbar(0,'Building data structures');
load cylinder
numn = size(p,1);
numt = size(t,1);
vect = 1:numt;
% DETERMINE UNIQUE EDGES IN MESH
e = [t(:,[1,2]); t(:,[2,3]); t(:,[3,1])]; % Edges - not unique
vec = (1:size(e,1))'; % List of edge numbers
[e,i,j] = unique(sort(e,2),'rows'); % Unique edges 确保每条边是从左到右嘛
vec = vec(j); % Unique edge numbers
eINt = [vec(vect), vec(vect+numt), vec(vect+2*numt)]; % Unique edges in each triangle
waitbar(0.2,w);
% DETERMINE EDGE TO TRIANGLE CONNECTIVITY
% Each row has two entries corresponding to the triangle numbers
% associated with each edge. Boundary edges have one entry = 0.
nume = size(e,1);
e2t = repmat(0,nume,2); %repmat 重复数组
ndx = repmat(1,nume,1);
for k = 1:numt
% Edge in kth triangle 每条边相邻的两个三角形编号
e1 = eINt(k,1); e2 = eINt(k,2); e3 = eINt(k,3);
% Edge 1
e2t(e1,ndx(e1)) = k; ndx(e1) = ndx(e1)+1;
% Edge 2
e2t(e2,ndx(e2)) = k; ndx(e2) = ndx(e2)+1;
% Edge 3
e2t(e3,ndx(e3)) = k; ndx(e3) = ndx(e3)+1;
end
waitbar(0.4,w);
% DETERMINE NODE TO EDGE CONNECTIVITY
% Determine maximum neighbours
j = e(:);
v = repmat(0,max(j),1);
for k = 1:length(j)
jk = j(k); v(jk) = v(jk)+1;
end
maxN = max(v);
n2e = repmat(0,numn,maxN+1);
ndx = repmat(1,numn,1);
for k = 1:nume
% End nodes
n1 = e(k,1); n2 = e(k,2);
% Connectivity
n2e(n1,ndx(n1)) = k; ndx(n1) = ndx(n1)+1;
n2e(n2,ndx(n2)) = k; ndx(n2) = ndx(n2)+1;
end
waitbar(0.6,w);
% DETERMINE NODE TO NODE CONNECTIVITY
n2n = repmat(0,numn,maxN+1);
for k = 1:numn
next = 1; m = 1;
while n2e(k,m)>0
if e(n2e(k,m),1)==k
n2n(k,next) = e(n2e(k,m),2); next = next+1;
else
n2n(k,next) = e(n2e(k,m),1); next = next+1;
end
m = m+1;
end
end
waitbar(0.8,w);
% FLAG BOUNDARY ELEMENTS
vec = (1:nume)'; % Edge list
be = vec(~all(e2t,2)); % Boundary edges
bn = e(be,:);
bn = unique(bn(:)); % Boundary nodes
bnd = false(numn,1);
bnd(bn) = true; % True for boundary nodes
% IMPORTANT MESH DATA
d = sqrt(sum((p(e(:,2),:)-p(e(:,1),:)).^2,2)); % Edge lengths
pc = (p(t(:,1),:)+p(t(:,2),:)+p(t(:,3),:))/3; % Centroids
pe = 0.5*(p(e(:,1),:)+p(e(:,2),:)); % Edge midpoints
% MEDIAN CELL PARAMETERS
hnx = repmat(0,nume,2);
hny = hnx;
A = repmat(0,numn,1);
for k = 1:nume
% Nodes and triangles
n1 = e(k,1); n2 = e(k,2);
t1 = e2t(k,1); t2 = e2t(k,2);
% xy nodes
x1 = p(n1,1); y1 = p(n1,2);
x2 = p(n2,1); y2 = p(n2,2);
% Edge midpoint
mx = 0.5*(x1+x2);
my = 0.5*(y1+y2);
% MEDIAN EDGE 1
% Cell centroid
cx = pc(t1,1);
cy = pc(t1,2);
% Area contribution
ac = 0.5*((mx-x1)*(cy-y1)-(my-y1)*(cx-x1));
A(n1) = A(n1)+abs(ac);
A(n2) = A(n2)+abs(0.5*((mx-x2)*(cy-y2)-(my-y2)*(cx-x2)));
% Edge normal
dx = cx-mx;
dy = cy-my;
hnx(k,1) = sign(ac)*dy;
hny(k,1) = -sign(ac)*dx;
% MEDIAN EDGE 2
if t2>0
% Cell centroid
cx = pc(t2,1);
cy = pc(t2,2);
% Area contribution
ac = 0.5*((mx-x1)*(cy-y1)-(my-y1)*(cx-x1));
A(n1) = A(n1)+abs(ac);
A(n2) = A(n2)+abs(0.5*((mx-x2)*(cy-y2)-(my-y2)*(cx-x2)));
% Edge normal
dx = cx-mx;
dy = cy-my;
hnx(k,2) = sign(ac)*dy;
hny(k,2) = -sign(ac)*dx;
else
for q = 1:3
if eINt(t1,q)==k
if q==3, z = 1; else z = q+1; end
% Boundary edge normals
hnx(k,2) = 0.5*(p(t(t1,z),2)-p(t(t1,q),2));
hny(k,2) = -0.5*(p(t(t1,z),1)-p(t(t1,q),1));
end
end
end
end
waitbar(1,w);
% CELL DATA STRUCTURE
eINt = uint32(eINt);
e2t = uint32(e2t);
n2e = uint32(n2e);
n2n = uint32(n2n);
data = struct('p' ,p ,... % Nodes
'e' ,e ,... % Edges
't' ,t ,... % Triangles
'pc' ,pc ,... % Centroids
'pe' ,pe ,... % Edge midpoints
'd' ,d ,... % Edge length
'hnx' ,hnx ,... % Median cell face normals
'hny' ,hny ,... % (pre-multiplied by face length)
'A' ,A ,... % Median cell area
'bnd' ,bnd ,... % True for boundary nodes
'be' ,be ,... % Boundary edges
'eINt' ,eINt ,... % Triangles as edges
'e2t' ,e2t ,... % Edge to triangle connectivity
'n2e' ,n2e ,... % Node to edge connectivity
'n2n' ,n2n ); % Node to node connectivity
close(w)
return
