Discussion Forum

Hi Chan,
If I well understand, you would like to create a 3D solid model starting from a like .stl format (you have vertices and faces which connect them). If so, you can try by first creating the 3D faces (by using "face3") and then using the function "geomcoerce('solid',geomObj)" to merge all faces and to get out the solid geometry in comsol.
Try, and let me know how it works.

Have a look to this pseudo-cose:

%%
for I=1:nFace %% number of faces...
Vertex=[X,Y,Z];

f=face3(Vertex(1),Vertex(2),Vertex(3)); %- creating 3d face
faceObj{i}=f;
end

%-then...
geomSolid=geomcoerce('solid',faceObj); %%% calculate the solid object...
%%

Keep mind that to obtain a solid object the input "vertex+faces" have to embed a closed domain.

Good luck

Pasquale

Thank you very much for your reply.

Actually, I had made a group of 3D surfaces using face3, exactly as you told me.
So, what I am trying to do is to make 3D solid object which contains the composite surface as a face.
For that purpose, I tried 3 methods but all in vain, because of the shortage of knowledge.

1) make 3D surface directily using the face or vertices that I have as you told me.
2) make a dummy solid object and split it by the composite surface
3) use extrusion

3) seemed impossible because the surface is not confined to 2D plane.
Regarding 2), I totally have no idea about how to do in COMSOL.
About 1), I am glad if I can following up your comments.
Excuse me for not understanding your comments thoroughly.

Can you give me an example for your syntax for 'geomcoerce'?

So far, I have believed that 'geomcoerce' cannot transform the 'dimension' of object.
But according to your current comments, it seems possible.

Also, if either of option 2), 3) is possible, can you let me know?

I really appreciate your kind attention and be hoping to get your reply again.
Thanks,

Hi Chan,

here's a simple matlab code:

function solidObj=create3DDomain(Vertex,Face)

%% INPUT:
% Vertex: vertices matrix.
% Face: faces matrix

%% OUTPUT:
% solidObj: comsol Solid Obj.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% written by Pasquale Franciosa, MIT, Boston, Sept. 10, 2009.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% Example:
% Face=[1 2 3 4;
% 5 6 7 8
% 3 4 8 7
% 1 2 6 5
% 2 6 7 3
% 1 4 8 5];
%
% Vertex=[0 0 0
% 100 0 0
% 100 100 0
% 0 100 0
% 0 0 100
% 100 0 100
% 100 100 100
% 0 100 100];

% solidObj=create3DDomain(Vertex,Face);
% geomplot(solidObj)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
nFace=size(Face,1);

fObj=cell(1,nFace);
for I=1:nFace
f=Face(I,:);
localVertex=Vertex(f,:);

X=[localVertex(1,1),localVertex(2,1);localVertex(4,1),localVertex(3,1)];
Y=[localVertex(1,2),localVertex(2,2);localVertex(4,2),localVertex(3,2)];
Z=[localVertex(1,3),localVertex(2,3);localVertex(4,3),localVertex(3,3)];

fObj{I}=face3(X,Y,Z); %%% X, Y, Z control the degree of the rational bezier patch... (see comsol help for info)...

end

solidObj=geomcoerce('solid',fObj); %%% create the solid object...


try to use it and let me know.

Regards

Pasquale

Thank you very much.

I succeeded in making the geometry you gave me as a sample.

But I failed in making arbitrary geometry that I wanted to make.

As a sample, I tried to make a tetrahedron using four faces defining that solid
, no error message. but only void space emerged.

Also, I could not make the geometry I tried to make,

Let me try myself more and contact you again.

Thank you again.

Eventually, I succeeded in making the geometry that I intended to make.

It is a group of solids that has 3D surface, and the group consists of about 1000 solids components.

So, the running is extremely slow and unstable, uniting the solid components and some other geometrical operations, and making mesh is impossible.

So, I am thinking of other methods.

Thank you very much for your help.

Sincerely,

Hi Chan
I hope you can solve your problem.
If you have any news about your solution, please let me know.

Good luck

Pasquale

hello

I have the same probleme.
Did you find a solution ?

thanks

Marie

Hi Pasquale,

thanks for your example, looks very useful to me as well. but where do you find create3DDomain? It's not in COMSOL or Matlab, is it? google doesn't find it ..

Best regards and thanks in advance,
Susanne

sorry, just disregard previous message - grabbing a coffee NOW ..

Hi Pasquale,

thanks for your example, looks very useful to me as well. but where do you find create3DDomain? It's not in COMSOL or Matlab, is it? google doesn't find it ..

Best regards and thanks in advance,
Susanne

Hi all,
actually, after half an hour trying with the code (me being new to Matlab AND COMSOL), I figured that the example code, in order to run, should read in the first line

function fObj=create3DDomain(Vertex,Face)

NOT

function solidObj=create3DDomain(Vertex,Face)

Cheers,
Susanne

and that was wrong again - sorry guys, I will just shut up now

Hi all,
actually, after half an hour trying with the code (me being new to Matlab AND COMSOL), I figured that the example code, in order to run, should read in the first line

function fObj=create3DDomain(Vertex,Face)

NOT

function solidObj=create3DDomain(Vertex,Face)

Cheers,
Susanne