How to export 3D spheres (3D plot) generated in Matlab to ANSYS or Abaqus. ?

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Sadeep Thilakarathna 2018-7-5

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评论： Biltu Mahato 2018-10-17

 I want to export 3D spheres generated in Matlab to ANSYS or Abaqus. 3D spheres are randomly generated and I want to mesh the 3D spheres and analyse those. Can anyone help me to export the 3D sphere plot to any meshing software like Gmsh or Ansys or Abaqus?

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Anton Semechko 2018-7-5

The spheres in your image, are they represented by level-sets of an implicit function?

Sadeep Thilakarathna 2018-7-6

Hi..These spheres are randomly generated such that they do not overlap.ellipsoid function in Matlab is used.

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Answer 1

Anton Semechko 2018-7-6

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编辑：Anton Semechko 2018-7-6

在 MATLAB Online 中打开

The builtin 'ellipsoid' and 'sphere' functions produce bad quality meshes (in terms of element shapes and connectivity of the vertices). You can get much better quality meshes using functions from here.

Here are is an example:

% Unit sphere based on subdivision of an icosahedron; triangular mesh
TRa=SubdivideSphericalMesh(IcosahedronMesh,4);
% Unit sphere based on subdivision of a cube; quadrilateral mesh
TRb=SubdivideSphericalMesh(QuadCubeMesh,4);
% Visualize
figure('color','w')
subplot(1,3,1)
h=trimesh(TRa); 
set(h,'EdgeColor','k','FaceColor',[0.9 0.9 0.9],'EdgeAlpha',0.5);
axis equal off vis3d
view([30 30])
zoom(1.5)
avp=GetAxesViewProps(gca);
ha=subplot(1,3,2);
h=patch(TRb); 
set(h,'EdgeColor','k','FaceColor',[0.9 0.9 0.9],'EdgeAlpha',0.5);
axis equal off vis3d
MatchAxesView(avp,ha)
% Plot sphere generated with built-in 'sphere' function for comparison
ha=subplot(1,3,3);
[X,Y,Z]=sphere(20);
h=surf(X,Y,Z);
set(h,'EdgeColor','k','FaceColor',[0.9 0.9 0.9],'EdgeAlpha',0.5);
axis equal off vis3d
MatchAxesView(avp,ha)

Functions 'GetAxesViewProps' and 'MatchAxesView' used in this example can be downloaded from here.

1) When exporting the meshes, do you want the program to recognize the individual spheres or would it be OK if the their face-vertex connectivity lists were merged (so you would have a single mesh containing multiple disconnected spheres)?

2) What type of meshes will you be generating after exporting the spheres; hexahedral or tetrahedral?

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Anton Semechko 2018-7-6

编辑：Anton Semechko 2018-7-10

在 MATLAB Online 中打开

Below is an example of how you can export multiple spheres to a .msh file (Gmsh standard). Assuming you already got the functions for generating spheres from here, for this example to work, you will also need to get functions 'gmsh_mesh2d_write.m' and 'mesh_base_one.m' from here. Let me know if you run into any problems.

function sphere_mesh_export_demo
% Suppose you have N spheres. Let C and R be N-by-3 and N-by-1 arrays
% containing centroid coordinates and radii of the spheres, respectively.
% As an example, I will use N=10, R=linspace(0.1,0.3,N), and distribute 
% spheres along the x-axis without them touching one another.
N=10;
R=1:N;
C=zeros(N,3); % initialize centroid coordinates
ds=min(R)/10; % separation between closest points on two adjacent spheres
for n=2:N
    C(n,1)=C(n-1,1) + R(n-1) + R(n) + ds;
end
% Step 1: Get mesh of a unit sphere 
n_sub=4;                                              % number of icosahedron subdivisions 
TRo=SubdivideSphericalMesh(IcosahedronMesh,n_sub);    % mesh will have Nv=10*4^n_sub+2 vertices and Nf=2*Nv-4 faces
[Fo,Vo]=GetMeshData(TRo);                             % Fo is a Nf-by-3 array of faces and Vo is a Nv-by-3 array of vertex coordinates  
% Step 2: Generate a composite mesh with spheres distributed accroding to C and R
Nv=size(Vo,1);
[F,V]=deal(cell(N,1));
for n=1:N    
    V{n}=bsxfun(@plus,R(n)*Vo,C(n,:));                % scale and translate TRo to get a sphere with radius R(n) and centroid C(n,:)
    F{n}=Fo+(n-1)*Nv;                                 % face-vertex connectivity of the n-th sphere 
end
V=cell2mat(V);                                        % compposite list of vertices 
F=cell2mat(F);                                        % composite list of faces
% Visualize result
figure('color','w')
h=patch('Faces',F,'Vertices',V);
set(h,'EdgeColor','none','FaceColor',0.75*[1 1 1],'FaceAlpha',0.5);
axis equal off
camlight('headlight')
lighting phong
material('dull')
%keyboard
% Step 3: Export mesh represented by F and V to a .msh file (Gmsh standard)
FileName='SphereMeshDemo.msh';
gmsh_mesh2d_write(FileName,...
                  3,...
                  size(V,1),...
                  V',...
                  3,...
                  size(F,1),...
                  F');

Sadeep Thilakarathna 2018-7-12

Yes...I wanted to generate volumetric meshes in Abaqus. However, when the a surface mesh is imported in to software, it cannot be remeshed. There is a plugin to convert the mesh in to the geometric model again in Abaqus. However, when it is converted to the geometry it will become a surface and volumetric meshes cannot be applied to the model. Thank you very much for the solutions you gave me. I will try to use the iso2mesh as well.

Biltu Mahato 2018-10-17

How did you assign material properties to .stl file? Abaqus doesn't let me assign material properties in Abaqus for .stl file imported from Matlab.

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How to export 3D spheres (3D plot) generated in Matlab to ANSYS or Abaqus. ?

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How to export 3D spheres (3D plot) generated in Matlab to ANSYS or Abaqus. ?

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