[chrono] Revolute joint

[Davide]

Hi everyone,
I'm trying to make a pendulum constraining it using a revolute joint. It 
gives me no error, but it doesn't oscillate and i'm not understanding why. 
Anyone might help me please?

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#include "chrono/physics/ChSystemNSC.h"
#include "chrono/physics/ChBodyEasy.h"
#include "chrono/physics/ChLinkMate.h"
#include "chrono/assets/ChTexture.h"
#include "chrono/core/ChRealtimeStep.h"
#include "chrono/physics/ChLinkLock.h"
#include "chrono_irrlicht/ChVisualSystemIrrlicht.h"

// Use the namespace of Chrono
using namespace chrono;
using namespace chrono::irrlicht;

int main(int argc, char* argv[]) {
    // Set path to Chrono data directory
    SetChronoDataPath(CHRONO_DATA_DIR);
    
    // Create a Chrono physical system
    ChSystemNSC sys;


   
    // 1 - Create a floor that is fixed (that is used also to represent the 
absolute reference)

    auto floorBody = std::make_shared<ChBodyEasyBox>(10, 2, 10,  // x, y, z 
dimensions
                                                     3000,       // density
                                                     true,       // create 
visualization asset
                                                     false       // no 
collision geometry
                                                     );
    floorBody->SetPos(ChVector<>(0, -2, 0));
    floorBody->SetBodyFixed(true);

    sys.Add(floorBody);

    // 2 - Create a pendulum
    auto pendulumBody = chrono_types::make_shared<ChBody>();
    sys.AddBody(pendulumBody);
    pendulumBody->SetIdentifier(1);
    pendulumBody->SetBodyFixed(false);
    pendulumBody->SetCollide(false);
    pendulumBody->SetMass(1);
    pendulumBody->SetInertiaXX(ChVector<>(0.2, 1, 1));

    // Initial position of the pendulum (horizontal, pointing towards positive 
X).
    pendulumBody->SetPos(ChVector<>(0, 3, 0));

    // Attach visualization assets.
    auto cyl_p = chrono_types::make_shared<ChCylinderShape>(0.5, 2);
    cyl_p->SetColor(ChColor(0.6f, 0, 0));
    pendulumBody->AddVisualShape(cyl_p, ChFrame<>(VNULL, 
Q_from_AngX(CH_C_PI_2)));

    // 3 - Create a revolute joint.
    auto revolute_link = chrono_types::make_shared<ChLinkLockRevolute>();
    revolute_link->Initialize(floorBody, 
pendulumBody,ChCoordsys<>(ChVector<>(0,3,0)));
    sys.Add(revolute_link);


    // Optionally, set color and/or texture for visual assets
    pendulumBody->GetVisualShape(0)->SetColor(ChColor(0.2f, 0.5f, 0.25f));
    
floorBody->GetVisualShape(0)->SetTexture(GetChronoDataFile("textures/bluewhite.png"),
 2, 2);

    // 4 - Create the Irrlicht visualization system
    ChVisualSystemIrrlicht vis;
    vis.SetWindowSize(800, 600);
    vis.SetWindowTitle("A simple project template");
    vis.Initialize();
    vis.AddLogo();
    vis.AddSkyBox();
    vis.AddTypicalLights();
    vis.AddCamera(ChVector<>(2, 2, -5), ChVector<>(0, 1, 0));
    vis.AttachSystem(&sys);

    // 5 - Simulation loop
    ChRealtimeStepTimer realtime_timer;
    double step_size = 5e-3;

    while (vis.Run()) {
        // Render scene
        vis.BeginScene();
        vis.Render();
        vis.EndScene();

        // Perform the integration stpe
        sys.DoStepDynamics(step_size);

        // Spin in place to maintain soft real-time
        realtime_timer.Spin(step_size);
    }

    return 0;
}