[SOLVED] Issue while exporting tetrahedron mesh generated from polyhedron

[Singh]

Hello,

Following is my scene file.

<?xml version="1.0"?>
<Node name="root" dt="0.05" showBoundingTree="0" gravity="0 -9 1">
    <VisualStyle displayFlags="showVisual" />
    <RequiredPlugin pluginName="CGALPlugin"/>

    <MeshObjLoader name="loader" filename="mesh/test.obj" />

    <Node name="visu_surface">
        <MechanicalObject name="dofs" position="@../loader.position"/>
        <TriangleSetTopologyContainer name="topo" triangles="@../loader.triangles"/>
        <TriangleSetTopologyModifier   name="Modifier" />
        <TriangleSetTopologyAlgorithms name="TopoAlgo"   template="Vec3d" />
        <TriangleSetGeometryAlgorithms template="Vec3d" name="GeomAlgo" drawTriangles="1" />
    </Node>

    <Node name="tetra_mesh">
        <MeshGenerationFromPolyhedron name="MeshGenerator" inputPoints="@../loader.position" inputTriangles="@../loader.triangles" inputQuads="@../loader.quads"/>
        <MechanicalObject name="dofs" position="@MeshGenerator.outputPoints"/>
        <TetrahedronSetTopologyContainer name="topo" tetrahedra="@MeshGenerator.outputTetras"/>
        <TetrahedronSetGeometryAlgorithms template="Vec3d" name="GeomAlgo" drawTetrahedra="1" drawScaleTetrahedra="0.8"/>
    </Node>
    
    <VTKExporter name="exporter" filename="mesh/test_out"  XMLformat="1" edges="0" tetras="1"  listening="true" exportAtBegin="true" cellsDataFields="MeshGenerator.outputCellData" overwrite="true"/>
</Node>

I get following error: [ERROR] [VTKExporter(exporter)] Error creating file mesh/test_out.vtu

Is there some issue with my VTKExporter statement?
Am I correct in writing this: cellsDataFields=”MeshGenerator.outputCellData”

[Hugo]

Hi @sukhraj

It seems the path is an issue. Could you try just with “test_out” ?

Regarding the MeshGenerator, it has only two outputs names: MeshGenerator.outputPoints and MeshGenerator.outputTetras. Your writing is therefore incorrect, it should raise an error right?

Best,

Hugo

[Singh]

@hugo
Thanks for your inputs.
I am new to SOFA and that is my first attempt at creating a scene file 🙂

Now I understand that:
MeshGenerator.outputPoints gives me point/geometry information.
and MeshGenerator.outputTetras gives me topological information. And I could see the same in the code:

, f_newX0( initData (&f_newX0, "outputPoints", "New Rest position coordinates from the tetrahedral generation"))
    , f_tetrahedra(initData(&f_tetrahedra, "outputTetras", "List of tetrahedra"))

Then what should be the input to the cellDataFields?

<VTKExporter name="exporter" filename="test_out" XMLformat="1" edges="0" tetras="1" listening="true" exportAtBegin="true" cellsDataFields="MeshGenerator.outputTetras" overwrite="true"/>

I see an empty file test_out.vtk and the application never seems to finish writing.
I could not find an example scene that shows exporting a tetrahedral mesh generated from a surface mesh.

Cheers,
Sukhraj

[jnbrunet]

Hey Sukhraj,

Glad that you are trying out SOFA!

The VTKExporter works by looking in its context (the <Node></Node> that contains it) in order to find a topology container ( [.*]SetTopologyContainer). It will then write the elements found in this topology.

Looking quickly at your scene, you should probably move the VTKExporter to get something like this:

<?xml version="1.0"?>
<Node name="root" dt="0.05" showBoundingTree="0" gravity="0 -9 1">
    <VisualStyle displayFlags="showVisual" />
    <RequiredPlugin pluginName="CGALPlugin"/>

    <MeshObjLoader name="loader" filename="mesh/test.obj" />

    <Node name="visu_surface">
        <MechanicalObject name="dofs" position="@../loader.position"/>
        <TriangleSetTopologyContainer name="topo" triangles="@../loader.triangles"/>
        <TriangleSetTopologyModifier   name="Modifier" />
        <TriangleSetTopologyAlgorithms name="TopoAlgo"   template="Vec3d" />
        <TriangleSetGeometryAlgorithms template="Vec3d" name="GeomAlgo" drawTriangles="1" />
    </Node>

    <Node name="tetra_mesh">
        <MeshGenerationFromPolyhedron name="MeshGenerator" inputPoints="@../loader.position" inputTriangles="@../loader.triangles" inputQuads="@../loader.quads"/>
        <MechanicalObject name="dofs" position="@MeshGenerator.outputPoints"/>
        <TetrahedronSetTopologyContainer name="topo" tetrahedra="@MeshGenerator.outputTetras"/>
        <TetrahedronSetGeometryAlgorithms template="Vec3d" name="GeomAlgo" drawTetrahedra="1" drawScaleTetrahedra="0.8"/>
        <VTKExporter name="exporter" filename="test_out" XMLformat="1" edges="0" tetras="1" listening="true" exportAtBegin="true" overwrite="true"/>
    </Node>
</Node>

Note that I removed the cellsDataFields attribute, as it isn’t used to stored the mesh topology, but rather some “field values” that you would like to store for each elements (cells).

Hope that helps.
J-N

[Singh]

Thanks, @jnbrunet,
Exactly that was the issue with the scene file, I have been able to export the tet mesh.

Thanks for helping out!

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