[SOLVED] printing_with_VTKExporter

[ewpostek]

Hello Colleagues,

I do attempt to print forces from the example:
StandardTetrahedralFEMForceField.scn (from the directory Components).
Therefore, I checked the action of the vtkexporter
that was placed in the three possible places.
However, I can get only displacements.
For the second case, counting from the top, I obtain
the dofs.force field but all the forces are zeros
(impossible).

Could anyone help with it ?

thank you,
Elek

<?xml version="1.0" ?>
<Node name="root" dt="0.3" showBoundingTree="0" gravity="0 0 -0.0">
    <CollisionPipeline verbose="0" name="CollisionPipeline" />
    <BruteForceDetection name="N2" />
    <CollisionResponse response="default" name="collision response" />
    <DiscreteIntersection />

    <Node name="MeshTopology">
        <TetrahedronSetTopologyContainer name="Container1" fileTopology="mesh/cylinder.msh" />
        <TetrahedronSetGeometryAlgorithms name="GeomAlgo" />
        <MechanicalObject name="dofs" />
        <Node name="FastTetrahedronCorotationalForceField">
            <CGLinearSolver iterations="500" name="linear solver" tolerance="1.0e-9" threshold="1.0e-9" />
            <StaticSolver applyIncrementFactor="1" />
            <TetrahedronSetTopologyContainer name="Container2" />
            <TetrahedronSetGeometryAlgorithms drawEdges="1" drawColorEdges="0 1 0" name="GeomAlgo" />
            <SimpleTesselatedTetraTopologicalMapping input="@Container1" output="@Container2" />
            <MechanicalObject translation="0 0 0" />
            <MeshMatrixMass name="mass" lumping="1" printMass="0" massDensity="10000" />
            <BoxROI box="-1.2 -1.2 -0.01 1.2 1.2 0.01" drawBoxes="1" name="fixedPlane2"  />
            <FixedConstraint indices="@fixedPlane2.indices" />
            <BoxROI box="-1.2 -1.2 0.99 1.2 1.2 1.01" drawBoxes="1" name="pressurePlane2"  />
            <ConstantForceField points="@pressurePlane2.indices" totalForce="0.001 0  -0.01" />
            <StandardTetrahedralFEMForceField materialName="NeoHookean" ParameterSet="0.454545 0.4166667"  />

            <VTKExporter name="vTKExporter" listening="true" pointsDataFields="dofs.force" filename="test_2a"  edges="1" triangles="1" quads="1" tetras="1" hexas="1" exportEveryNumberOfSteps="1" />

        </Node>
        <VTKExporter name="vTKExporter" listening="true" pointsDataFields="dofs.force" filename="test_2a" edges="1" triangles="1" quads="1" tetras="1" hexas="1" exportEveryNumberOfSteps="1" />
    </Node>
    <VTKExporter name="vTKExporter" listening="true" pointsDataFields="dofs.force" filename="test_2a" edges="1" triangles="1" quads="1" tetras="1" hexas="1" exportEveryNumberOfSteps="1" />
</Node>

[Hugo]

Hi Elek,

The data “pointDataField” should indeed be the one for saving additional data. But why did you use 3 VTKExporters ? Using only the second one should work (using the path pointsDataFields=”dofs.force”) and removing the two others:

...
            <ConstantForceField points="@pressurePlane2.indices" totalForce="0.001 0  -0.01" />
            <StandardTetrahedralFEMForceField materialName="NeoHookean" ParameterSet="0.454545 0.4166667"  />

        </Node>

        <VTKExporter name="vTKExporter" listening="true" pointsDataFields="dofs.force" filename="test_2a" edges="1" triangles="1" quads="1" tetras="1" hexas="1" exportEveryNumberOfSteps="1" />
        
    </Node>

</Node>

Another trick, could be to export the position with one VTKExporter and to export the forces using a second VTKExporter where position=”dofs.force”.

Hope this helps.

Hugo

[ewpostek]

Hi Hugo,
The problem is that when putting the
vtkExporter at the second place (correctly) I do not
obtain neither displacements (deformed structure)
nor forces.
The files from the step one or step 10 are the same.
I run the example in the interactive mode. It gives
the deformation.

There are zeros the the end

<VTKFile type=”UnstructuredGrid” version=”0.1″ byte_order=”BigEndian”>
<UnstructuredGrid>
<Piece NumberOfPoints=”510″ NumberOfCells=”10589″>
<PointData>
<DataArray type=”Float64″ Name=”force” NumberOfComponents=”3″ format=”ascii”>
0 0 0
0 0 0
0 0 0

I applied different combinations of the parameters but
it gave me the same result.

I see that the vtkExporter should not
be put on the place “one” because the mechanical
object is defined above the node <Node name=”FastTetrahedronCorotationalForceField”>
(I believe ?).

However, “experimentally”, while putting the vtkExporter at the position “one”
I have got a deformation. However, it’s true I do
not know if this is right (correct).
Morover, there is the error:

[WARNING] [VTKExporter] VTKExporter : error while fetching data field 'force' of object 'dofs', check object name

best, Elek

[Hugo]

Hi Elek,

Sorry I read your scene file too fast.
Some things were not making sense: your MechanicalObject was missing a name (so you can’t recover its data), and the way you load the topology was wrong.

Here is a suggestion:

<?xml version="1.0" ?>
<Node name="root" dt="0.3" showBoundingTree="0" gravity="0 0 -0.0">
    <CollisionPipeline verbose="0" name="CollisionPipeline" />
    <BruteForceDetection name="N2" />
    <CollisionResponse response="default" name="collision response" />
    <DiscreteIntersection />

    <Node name="MeshTopology">
        
        <MeshGmshLoader name="GmshLoader" filename="mesh/cylinder.msh" createSubelements="true" />
        <TetrahedronSetTopologyContainer name="Container1" src="@GmshLoader" />
        <TetrahedronSetGeometryAlgorithms template="Vec3d" name="GeomAlgo" />
        <MechanicalObject template="Vec3d" name="dofs" />

        <Node name="FastTetrahedronCorotationalForceField">
            <CGLinearSolver iterations="500" name="linear solver" tolerance="1.0e-9" threshold="1.0e-9" />
            <StaticSolver applyIncrementFactor="1" />
            <TetrahedronSetTopologyContainer name="Container2" />
            <TetrahedronSetGeometryAlgorithms template="Vec3d" drawEdges="1" drawColorEdges="0 1 0" name="GeomAlgo" />
            <SimpleTesselatedTetraTopologicalMapping input="@Container1" output="@Container2" />
            <MechanicalObject template="Vec3d" name="mecaDOFs" translation="0 0 0" />
            <MeshMatrixMass name="mass" lumping="1" printMass="0" massDensity="10000" />
            <StandardTetrahedralFEMForceField materialName="NeoHookean" ParameterSet="0.454545 0.4166667"  />

            <BoxROI template="Vec3d" box="-1.2 -1.2 -0.01 1.2 1.2 0.01" drawBoxes="1" name="fixedPlane2"  />
            <BoxROI template="Vec3d"  box="-1.2 -1.2 0.99 1.2 1.2 1.01" drawBoxes="1" name="pressurePlane2"  />

            <FixedConstraint indices="@fixedPlane2.indices" />
            <ConstantForceField points="@pressurePlane2.indices" totalForce="0.001 0  -0.01" />

            <VTKExporter name="vTKExporter" listening="true" position="mecaDOFs.position" pointsDataFields="mecaDOFs.force" filename="test_2a"  edges="1" triangles="1" quads="1" tetras="1" exportEveryNumberOfSteps="1" />

        </Node>
    </Node>
</Node>

This is working for me.
Best,

Hugo

[ewpostek]

Hi Hugo,
Thank you very much for the template.
I obtained the displacements and forces in the test2a(_n).vtu files.
There is only one surprising comment from the program:

eligiusz@eligiusz-laptop:~/tmp_stable_sofa/tmp_exa/stan_t1$ /home/eligiusz/tmp_stable_sofa/sofa/v16.08/build/bin/runSofa -g batch -n 3 x2_hg.scn
[WARNING] [VTKExporter] File test_2a NOT FOUND in :/home/eligiusz/tmp_stable_sofa/sofa/v16.08/src/examples:/home/eligiusz/tmp_stable_sofa/sofa/v16.08/src/share
File test_2a NOT FOUND in :/home/eligiusz/tmp_stable_sofa/sofa/v16.08/src/examples:/home/eligiusz/tmp_stable_sofa/sofa/v16.08/src/share
Could not read value for data field position: mecaDOFs.position
The model is NeoHookean
Computing 3 iterations.
3 iterations done in 3.32091 s ( 0.903368 FPS).
3 iterations done in 3.32091 s ( 0.903366 FPS).
eligiusz@eligiusz-laptop:~/tmp_stable_sofa/tmp_exa/stan_t1$

thank you,
Elek

[Hugo]

Yes it seems the link on position is not working well.
Maybe due to the fact the exporter already finds the MechanicalObject.
I will look at it.

Still I set the topic as solved since you achieved to recover your vtk files.

Cheers,

Hugo

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