HELP. How to extract the mass and stiffness matrix?

[artXuRo]

Hi,
I want to extract the mass and stiffness matrix during the FEM simulation. I build the fem model by python. Are there any APIs in SOFAPYTHON3 that can help me extract the matrix? Or any other way can get stiffness and mass matrix?

Best
Art, Xu

[hugtalbot]

Hey @artXuRo

Thanks for your question!
I think not yet, but @alxbilger is working on this : having possibly these matrices as Data so that as all Data you can access them in python.

Do you confirm Alex?

[artXuRo]

Thanks for your response!
We are now using an inefficient method to gain the system matrix. As do some estimates in 'onAnimateBeginEvent' to make sure whether we need the system matrix, if true, we set 'savingMatrixToFile' as True in SparseLDLsolver. And SOFA will store the file. In 'onAnimateEndEvent', we export some data and set ‘savingMatrixToFile’ as False.
It worked but some questions remain... just like we do not know which one is the Mass matrix in this file, and it's hard to reshape it into the format of matrix in Matlab。。。

Best
Art

[ozilxu]

@hugtalbot @artXuRo May I ask if the latest version of SOFA22 cannot extract the stiffness matrix? Thanks!

[alxbilger]

@ozilxu Sofa v22.06 is not yet released. Building the stiffness matrix will be available in the SofaPython3 plugin, hopefully for v22.06. Stay tuned.

[ozilxu]

@alxbilger Hi Alex, may I ask when will the compiled version of SofaV22.06 be released?

[alxbilger]

@hugtalbot would be the best person to ask. Probably end of June

[alxbilger]

Hi @artXuRo

Accessing stiffness and mass matrix is a work in progress.
If you are ready to experiment, you can find an open pull request on SofaPython3 to do what you want: sofa-framework/SofaPython3#262.
Any feedback is welcome.

Alex

[artXuRo]

I'm trying to....
T...T
The first time to compile SOFA and its plugin...Toooooo many errors I got...

[artXuRo]

Hi,
@alxbilger THANKS FOR YOUR WORK
I had successfully compile sofapython3 from sofa-framework/SofaPython3#262.
The example operate successfully, after I annotate from sofa import SofaLinearSolver...
When I running it, the animation is perfect, but the error is Unable to execute code. Python exception: KeyError: 'assembleKMatrix'

[alxbilger]

Thanks for trying an experimental feature.
You are right that from sofa import SofaLinearSolver should be removed.
I need to investigate why you have the error. I'll let you know

[artXuRo]

Hi @alxbilger
Now, it works perfectly on Unbuntu.
When I tried to compile it on windows, there had been some errors. Here are the messages from VS2019

[alxbilger]

Is it possible your version of SOFA on Windows is not up-to-date?

[artXuRo]

Hi, I recompile sofa and sofapython3, the error goes away~It seems caused by the old version of sofapython3. Now the plug-in runs perfectly. Fantastic work,Alex thanks too much! Best Art 发自我的iPhone

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在 2022年5月25日，20:24，Alex Bilger ***@***.***> 写道：  Thanks for trying an experimental feature. You are right that from sofa import SofaLinearSolver should be removed. I need to investigate why you have the error. I'll let you know — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you were mentioned.