Unable Incorporate new member variable to cariboutopology counterpart of splines implementation.

[bhagath555]

Hello Cariobu Community,

I am Bhagath, and I am currently working on the implementation of FEM analysis with splines (aka Isogeometric analysis) in Caribou.

So far :

• I have implemented costume spline element, which is similar to other elements in caribou
• topology container (called SplinePatch) that is equivalent to Mesh + Domain of caribou.
• geometry file reader that is equivalent to VTKReader.

I tested all of them individually, everything is working fine.

However, when I attempted to implement CaribouSplineTopology (CST), which should be equivalent to CaribouTopology (CT), I encountered an error. Please bear with me as I explain my problem in detail.

As CT has attachDomain function, In CST, I have implemented attachSplinePatch function. Which attaches SplinePatch function to CST class provides information such as position, indices and knot information.

In addition to already existing d_positions and d_indices member variables I am trying to attach d_knots variable to CST class. But, I am unable to write knot span data into d_knots variable using WriteonlyAccessor and it while doing so, It is returning segmentation fault error.

Please go through the below code snippets and suggest anything I am missing.

Thanks in advance.
Bhagath M

CaribouSplineTopology::CaribouSplineTopology()

// d_knots declarations, each vector item correspond to spline element in patch : 
Data<sofa::type::vector<sofa::type::fixed_array<Real, KnotDimension>>> d_knots;

template <typename Element>
CaribouSplineTopology<Element>::CaribouSplineTopology ()
: d_position(initData(&d_position,
    "position",
    "Position vector of the patch nodes."))
, d_indices(initData(&d_indices,
    "indices",
    "Node indices (w.r.t the position vector) of each elements."))
, d_knots(initData(&d_knots,
    "d_knots",
    "knot span of every element"))
{}

CaribouSplineTopology::attachSplinePatch

template <typename Element>
void CaribouSplineTopology<Element>::attachSplinePatch(const caribou::topology::SplinePatch<Dimension, PointID> * patch) {
    this->p_patch = patch;
    using namespace sofa::helper;
		int KnotDimension = 4; // for reference
    auto indices = WriteOnlyAccessor<Data<sofa::type::vector<sofa::type::fixed_array<PointID, NumberOfNodes>>>>(d_indices);
    auto knots = WriteOnlyAccessor<Data<sofa::type::vector<sofa::type::fixed_array<Real, KnotDimension>>>>(d_knots);
    const auto number_of_elements = patch->number_of_elements();
    indices.resize(number_of_elements);

    for (sofa::Index element_id = 0; element_id < number_of_elements; ++element_id) {
        const auto element_indices = patch->element_indices(element_id);
        const auto element_knots = patch->element_knotranges(element_id);
        for (sofa::Index node_id = 0; node_id < NumberOfNodes; ++node_id) {
            indices[element_id][node_id] = static_cast<PointID>(element_indices[node_id]);
        }
        for (sofa::Index node_id = 0; node_id < KnotDimension; ++node_id) {
            knots[element_id][node_id] = static_cast<Real>(element_knots[node_id]); 
        }
    }
}

[hugtalbot]

Hey @bhagath555

Thanks for your post and sorry for our latency.

I need some time to dig into Caribou API which I am not 100% familiar with.
Your problem could be related to the CRTP (C++ design pattern) massively used in the Caribou code base.

Let me also notice @Sidaty1 about this post

[hugtalbot]

Do you have any compilation error or does it just crash while running a scene ? @bhagath555

[bhagath555]

Hello @hugtalbot ,
Thank you for the response. The code is compiling and building well. But, When I ran the Caribou.unittests.SofaCaribou. It is prompting below error.

########## SIG 11 - SIGSEGV: segfault ##########
-> /home/bhagath/code/sofa/build/install/lib/libSofa.Helper.so.21.06.03(sofa::helper::BackTrace::dump()+0x27) [0x7fb6df66fd87]
-> /home/bhagath/code/sofa/build/install/lib/libSofa.Helper.so.21.06.03(sofa::helper::BackTrace::sig(int)+0x1d6) [0x7fb6df670126]
-> /lib/x86_64-linux-gnu/libc.so.6(+0x43090) [0x7fb6df0c7090]
-> /home/bhagath/code/plugins/caribou_IGA/build/lib/libSofaCaribou.so(SofaCaribou::topology::CaribouSplineTopology<caribou::geometry::BezierSurf<2ull> >::attachSplinePatch(caribou::topology::SplinePatch<2u, unsigned int, caribou::topology::EigenSplineNodesHolder<Eigen::Matrix<double, -1, 2, 1, -1, 2> > > const*)+0x161) [0x7fb6e19f4da1]
-> ./Caribou.unittests.SofaCaribou(+0x5e7a5) [0x5652a6aeb7a5]
-> /home/bhagath/code/sofa/build/install/lib/libgtest.so.2.6.2(void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)+0x51) [0x7fb6e07931c1]
-> /home/bhagath/code/sofa/build/install/lib/libgtest.so.2.6.2(testing::Test::Run()+0xd6) [0x7fb6e07885a6]
-> /home/bhagath/code/sofa/build/install/lib/libgtest.so.2.6.2(testing::TestInfo::Run()+0x135) [0x7fb6e0788705]
-> /home/bhagath/code/sofa/build/install/lib/libgtest.so.2.6.2(testing::TestSuite::Run()+0xfd) [0x7fb6e078882d]
-> /home/bhagath/code/sofa/build/install/lib/libgtest.so.2.6.2(testing::internal::UnitTestImpl::RunAllTests()+0x493) [0x7fb6e0788d93]
-> /home/bhagath/code/sofa/build/install/lib/libgtest.so.2.6.2(testing::UnitTest::Run()+0xd8) [0x7fb6e0788ff8]
-> ./Caribou.unittests.SofaCaribou(+0x204dc) [0x5652a6aad4dc]
-> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0x7fb6df0a8083]
-> ./Caribou.unittests.SofaCaribou(+0x2408e) [0x5652a6ab108e]
Segmentation fault (core dumped)

[Sidaty1]

Hi @bhagath555 and @hugtalbot,

@bhagath555, I can suggest two things,

Have you added the variable d_knots to your CaribouSplineTopology.h ?

Otherwise, let's meet virtually so I can have a better idea of your code.

Best,

[bhagath555]

Thank you @Sidaty1 for meeting.
Also, Thank you @hugtalbot.
It was just a resizing vector before assign values into it. ;)
Hopefully, I'll come with better problem next-time.
Cheers, have a nice day,
Bhagath