MATLAB: Trimesh and trisurf produces a very bad triangulation results?!!

trisurf

Hello! I am trying to model a closed surface, but trimesh and trisurf produces a very bad plot, how can I improve it?: is there any other functions to use instead ?! Thank you!! Note: below is the code I am using:

figure(1)
trisurf(t,p(1,:),p(2,:),p(3,:));title('ploted using trisurf ')
figure(2)
trimesh(t,p(1,:),p(2,:),p(3,:));title('ploted using trimesh ')

Best Answer

hello! the problem was that the triangles contained not only the nodes but also their domain number (inside or out side the object) so when I used only the nodes of the triangle it worked perfectely using:

(I meant by bad it generates parallelogram instead of triangles)

figure(1) trisurf(t(1:3,:),p(1,:),p(2,:),p(3,:));title('ploted using trisurf ')

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MATLAB: Cutting area plot matlab

What about this?

clc,clear
% generate surface
r = 0:0.1:5;
t = linspace(0,2*pi,30);
[T,R] = meshgrid(t,r);
Z = 5*sin(R)./R;
[X,Y] = pol2cart(T,R);
% data for cutting
x = [1 3 0.7];
y = [0.2 0.3 3];
z = [1 1.2 1];
ix = convhull(X(:),Y(:));           % boundary of surface

x1 = X(ix(1:end-2));                % vertices of boundary
y1 = Y(ix(1:end-2));
gd1 = [2; length(x1); x1(:); y1(:)];               % surface boundary geometry
gd2 = gd1;  
gd2(1:2+2*length(x)) = [2; length(x); x(:); y(:)]; % cutting plane boundary geometry
dl = decsg([gd1 gd2],'P1-P2',char('P1','P2')');    % decomposite geometry
[p,e,t] = initmesh(dl,'hmax',0.5);                 % create mesh
F = scatteredInterpolant(X(:),Y(:),Z(:));
zz = F(p(1,:),p(2,:));  % calculate Z coordinate for each mesh point
fv.vertices = [p;zz]';  % x y z data
fv.faces = t(1:3,:)';   % connection list of faces
cla
patch(fv,'facecolor','r')   % surface
patch(x,y,z,'g')            % cutting plane
view(150,45)
axis vis3d

If you have boundary intstead of convhull

ix = convhull(X(:),Y(:));           % boundary of surface

MATLAB: Convert a tetrahedron mesh to triangular mesh or surface mesh.

Easy. Assume that tess is an nx4 array, composed of references into the set of vertices.

Then surely is it true that:

facets = [tess(:,[1 2 3]);tess(:,[1 2 4]);tess(:,[1 3 4]);tess(:,[2 3 4])];

is a set of facets of those simplexes? So facets is the set of triangular facets as requested. But I think you asked for the outer boundary surface of the mesh.

The only problem is that some of those facets are replicated. That is, facets that are shared between a pair of touching simplexes will happen exactly twice. A facet that is on the surface will occur exactly once.

But in fact, these replicates are actually a good thing! If you are only looking for the surface triangulation, then you can discard those facets that occurred twice. It is important to sort them though. (Think! why?)

facets = sort(facets,2);

Now, how do we discard those duplicated?

facets = sortrows(facets);
duploc = find(all(diff(facets) == 0,2));
facets([duploc;duploc + 1],:) = [];

Best Answer

Related Solutions

MATLAB: Cutting area plot matlab

MATLAB: Convert a tetrahedron mesh to triangular mesh or surface mesh.

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