Introduction to FEA cables (demo_FEA_cables.cpp)

Tutorial that teaches how to use the FEA module to create basic FEA cables, that fall and swing under the effect of gravity. Some rigid bodies (boxes) are connected to the cables.

// =============================================================================
// PROJECT CHRONO - http://projectchrono.org
//
// Copyright (c) 2014 projectchrono.org
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file at the top level of the distribution and at
// http://projectchrono.org/license-chrono.txt.
//
// =============================================================================
// Authors: Alessandro Tasora, Radu Serban
// =============================================================================
//
// FEA for 3D beams of 'cable' type (ANCF gradient-deficient beams)
//
// =============================================================================
 
#include "chrono/physics/ChSystemSMC.h"
#include "chrono/solver/ChDirectSolverLS.h"
#include "chrono/solver/ChIterativeSolverLS.h"
#include "chrono/timestepper/ChTimestepper.h"
#include "chrono_irrlicht/ChIrrApp.h"
 
#include "FEAcables.h"
 
using namespace chrono;
using namespace chrono::fea;
using namespace chrono::irrlicht;
 
using namespace irr;
 
// Select solver type (SPARSE_QR, SPARSE_LU, or MINRES).
ChSolver::Type solver_type = ChSolver::Type::SPARSE_QR;
 
int main(int argc, char* argv[]) {
    GetLog() << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << "\n\n";
 
    // Create a Chrono::Engine physical system
    ChSystemSMC my_system;
 
    // Create the Irrlicht visualization (open the Irrlicht device,
    // bind a simple user interface, etc. etc.)
    ChIrrApp application(&my_system, L"Cables FEM", core::dimension2d<u32>(800, 600), false, true);
 
    // Easy shortcuts to add camera, lights, logo and sky in Irrlicht scene:
    application.AddTypicalLogo();
    application.AddTypicalSky();
    application.AddTypicalLights();
    application.AddTypicalCamera(core::vector3df(0.f, 0.6f, -1.f));
 
    // Create a mesh, that is a container for groups of elements and
    // their referenced nodes.
    auto my_mesh = chrono_types::make_shared<ChMesh>();
 
    // Create one of the available models (defined in FEAcables.h)
    auto model = Model3(my_system, my_mesh);
 
    // Remember to add the mesh to the system!
    my_system.Add(my_mesh);
 
    // ==Asset== attach a visualization of the FEM mesh.
    // This will automatically update a triangle mesh (a ChTriangleMeshShape
    // asset that is internally managed) by setting  proper
    // coordinates and vertex colors as in the FEM elements.
    // Such triangle mesh can be rendered by Irrlicht or POVray or whatever
    // postprocessor that can handle a colored ChTriangleMeshShape).
    // Do not forget AddAsset() at the end!
 
    auto mvisualizebeamA = chrono_types::make_shared<ChVisualizationFEAmesh>(*(my_mesh.get()));
    mvisualizebeamA->SetFEMdataType(ChVisualizationFEAmesh::E_PLOT_ELEM_BEAM_MZ);
    mvisualizebeamA->SetColorscaleMinMax(-0.4, 0.4);
    mvisualizebeamA->SetSmoothFaces(true);
    mvisualizebeamA->SetWireframe(false);
    my_mesh->AddAsset(mvisualizebeamA);
 
    auto mvisualizebeamC = chrono_types::make_shared<ChVisualizationFEAmesh>(*(my_mesh.get()));
    mvisualizebeamC->SetFEMglyphType(ChVisualizationFEAmesh::E_GLYPH_NODE_DOT_POS); // E_GLYPH_NODE_CSYS
    mvisualizebeamC->SetFEMdataType(ChVisualizationFEAmesh::E_PLOT_NONE);
    mvisualizebeamC->SetSymbolsThickness(0.006);
    mvisualizebeamC->SetSymbolsScale(0.01);
    mvisualizebeamC->SetZbufferHide(false);
    my_mesh->AddAsset(mvisualizebeamC);
 
    // ==IMPORTANT!== Use this function for adding a ChIrrNodeAsset to all items
    // in the system. These ChIrrNodeAsset assets are 'proxies' to the Irrlicht meshes.
    // If you need a finer control on which item really needs a visualization proxy in
    // Irrlicht, just use application.AssetBind(myitem); on a per-item basis.
    application.AssetBindAll();
 
    // ==IMPORTANT!== Use this function for 'converting' into Irrlicht meshes the assets
    // that you added to the bodies into 3D shapes, they can be visualized by Irrlicht!
    application.AssetUpdateAll();
 
    // Set solver and solver settings
    switch (solver_type) {
        case ChSolver::Type::SPARSE_QR: {
            std::cout << "Using SparseQR solver" << std::endl;
            auto solver = chrono_types::make_shared<ChSolverSparseQR>();
            my_system.SetSolver(solver);
            solver->UseSparsityPatternLearner(true);
            solver->LockSparsityPattern(true);
            solver->SetVerbose(false);
            break;
        }
        case ChSolver::Type::SPARSE_LU: {
            std::cout << "Using SparseLU solver" << std::endl;
            auto solver = chrono_types::make_shared<ChSolverSparseLU>();
            my_system.SetSolver(solver);
            solver->UseSparsityPatternLearner(true);
            solver->LockSparsityPattern(true);
            solver->SetVerbose(false);
            break;
        }
        case ChSolver::Type::MINRES: {
            std::cout << "Using MINRES solver" << std::endl;
            auto solver = chrono_types::make_shared<ChSolverMINRES>();
            my_system.SetSolver(solver);
            solver->SetMaxIterations(200);
            solver->SetTolerance(1e-10);
            solver->EnableDiagonalPreconditioner(true);
            solver->EnableWarmStart(true);  // IMPORTANT for convergence when using EULER_IMPLICIT_LINEARIZED
            solver->SetVerbose(false);
            break;
        }
        default: {
            std::cout << "Solver type not supported." << std::endl;
            break;
        }
    }
 
    my_system.SetSolverForceTolerance(1e-13);
 
    // Set integrator
    my_system.SetTimestepperType(ChTimestepper::Type::EULER_IMPLICIT_LINEARIZED);
 
    // SIMULATION LOOP
    application.SetTimestep(0.01);
 
    while (application.GetDevice()->run()) {
        application.BeginScene();
        application.DrawAll();
        application.DoStep();
        application.EndScene();
    }
 
    return 0;
}