[SOLVED] Components for quadratic meshes

[Zahra]

Hi,

I have three questions:

1. I try to simulate a deformable quadratic surface mesh (obj. mesh) that lies on a planeforcefield. I used the following components for object node:
– MeshObjLoader
– MechanicalObject
– UniformMass
– EulerImplicitSolver
– CGLinearSolver
– QuadularBendingSprings
– HexahedralFEMForceField
– PlaneForceField

Is this true?
Can I use HexahedralFEMForceField considering that my mesh is composed of quads? I can not find the appropriate quadratic component.

I also used these for Visual node:
– OGLModel
– BarycentricMapping

When I run it, Sofa stops working without any error.

2. I had no problem with triangular meshes, but when I want to change the mesh file from triangular to quad, I can not find the equivalent quadratic components (such as TriangularFEMForceField. There is no equivalent for quad).

3. Is there any more comprehensive reference rather than SOFA tutorial? The tutorial does not give enough information about components’s properties.

Thanks in advance.

Zahra

[Hugo]

Dear Zahra,

1. I think you misused the word “quadratic”. You meant quadrilateral (made of quads), right ? Then, you cannot use hexahedronFF if your mesh includes only quads: these are two different kind of elements (i.e. different shape functions). For simulations using quads, please refer to the examples: examples/Components/forcefield/QuadBendingSprings.scn

2. Indeed the QuadrilateralFEMForceField does not exist (has not been implemented) at my best knowledge. If you feel confident to do it, you are more than welcome to contribute.

3. In our simulations, we rarely use the quads indeed, the best is to look at the examples (and tutorials but you already did it!). Then, the next step would be to start the implementation.

Best regards,

Hugo

[Zahra]

Dear Hugo,

Thank you for your reply. Yes I meant quadrilateral.

Your proposed scene is using regularGridTopology which creates a regular mesh using only boundaries and the scaling without uploading any quadrilateral mesh. I also could not change the properties of this component to produce another quadilateral mesh as I do not have any knowledge about its properties. Besides, the simulated mesh becomes unstable during interactions in some conditions.

[Hugo]

Hi Zahra,

Indeed it is using a regularGridTopology. About the instabilities, there are just due to a wrong choice of time step. Here the implicit integration requires a smaller time step. No more instabilities are noticed when dt is set to 0.01.
About the quadrilateral FEM, I am sorry but not much is indeed existing. However, I would be more than happy to help you in developping a new FEMForceField with you in SOFA.

Cheers,

Hugo

[Zahra]

Dear Hugo,

Thank you for your kind reply. Yes changing time step resulted in no more instabilities.

I have changed the topology from quadrilateral to triangular for a while. If it works for my purpose, I would not need quadrilateral FEMForceField anymore. I will ask for your kind help in case I need to develop it in future.

Best,

Zahra

[Hugo]

Alright !

My pleasure, do not hesitate to contact us again.
I’ll close the topic.

Cheers,

Hugo

[PhoNguyen]

Hi,

I want to setup a forcefield for simulating a deformable quadrilateral surface mesh.
Are there any updated or related works in SOFA now?

Best,
Pho

[Author]

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