What is different QMorphingAnimation and QVertexBlendAnimation?

[Sugar]

Hi, I want to use Morph Animation with Qt3D.
I read the documents of QMorphingAnimation and QVertexBlendAnimation but I did not understand the difference well.
So, I tried while referring to the code in "Qt/5.13.0/Src/qt3d/tests/manual/mesh-morphing".
Here is the code I'm trying. ( Almost the same... )

When I run this cord, ASSERT failure in QVector<T>::at: "index out of range", file QtCore/qvector.h, line 440 comes out.
Is my usage strange?

I use Qt version 5.13.0.
Sorry, I am not good at English. Thanks in advance.

#include <QApplication>
#include <QMainWindow>
#include <QWidget>

#include <Qt3DRender/Qt3DRender>
#include <Qt3DCore/Qt3DCore>
#include <Qt3DInput/Qt3DInput>
#include <Qt3DExtras/Qt3DExtras>
#include <Qt3DAnimation/Qt3dAnimation>

void funcCameraSetting( Qt3DRender::QCamera* camera )
{
    camera->setProjectionType( Qt3DRender::QCameraLens::PerspectiveProjection );
    camera->setViewCenter( QVector3D( 0.0f, 0.0f, 0.0f ) );
    camera->setPosition( QVector3D( 10.0f, 10.0f, 10.0f ) );
    camera->setNearPlane( 0.1f );
    camera->setFarPlane( 1000.0f );
}

int main( int argc, char* argv[] )
{
    QApplication a( argc, argv );

    auto rootEntity = new Qt3DCore::QEntity();
    auto view = new Qt3DExtras::Qt3DWindow();
    view->defaultFrameGraph()->setClearColor( Qt::white );
    view->renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::OnDemand );
    funcCameraSetting( view->camera() );
    view->camera()->setAspectRatio( view->width() / view->height() );
    auto cameraControl = new Qt3DExtras::QOrbitCameraController( rootEntity );
    cameraControl->setCamera( view->camera() );

    /* base mesh*/
    auto mesh = new Qt3DExtras::QCylinderMesh( rootEntity );
    mesh->setRings( 6 );
    mesh->setSlices( 20 );
    /* target geometry*/
    auto cylinder1 = new Qt3DExtras::QCylinderGeometry( rootEntity );
    auto cylinder2 = new Qt3DExtras::QCylinderGeometry( rootEntity );
    auto cylinder3 = new Qt3DExtras::QCylinderGeometry( rootEntity );
    cylinder1->setRings( 6 );
    cylinder1->setSlices( 20 );
    cylinder1->setLength( 2.0f );
    cylinder1->setRadius( 1.0f );
    cylinder2->setRings( 6 );
    cylinder2->setSlices( 20 );
    cylinder2->setLength( 1.0f );
    cylinder2->setRadius( 5.0f );
    cylinder3->setRings( 6 );
    cylinder3->setSlices( 20 );
    cylinder3->setLength( 9.0f );
    cylinder3->setRadius( 1.0f );
    /* morph target setting */
    QStringList attributes;
    attributes.append( Qt3DRender::QAttribute::defaultPositionAttributeName() );
    attributes.append( Qt3DRender::QAttribute::defaultNormalAttributeName() );
    QVector<Qt3DAnimation::QMorphTarget*> morphTargets;
    morphTargets.append( Qt3DAnimation::QMorphTarget::fromGeometry( cylinder1, attributes ) );
    morphTargets.append( Qt3DAnimation::QMorphTarget::fromGeometry( cylinder3, attributes ) );
    morphTargets.append( Qt3DAnimation::QMorphTarget::fromGeometry( cylinder2, attributes ) );
    morphTargets.append( morphTargets.first() );
    /* transform and material */
    auto transform = new Qt3DCore::QTransform;
    auto material = new Qt3DExtras::QMorphPhongMaterial( rootEntity );
    material->setDiffuse( Qt::red );
    /* target entity */
    auto morphingEntity = new Qt3DCore::QEntity( rootEntity );
    morphingEntity->addComponent( mesh );
    morphingEntity->addComponent( transform );
    morphingEntity->addComponent( material );
    /* animation setting */
    auto animation1 = new Qt3DAnimation::QVertexBlendAnimation;
    auto animation2 = new Qt3DAnimation::QMorphingAnimation; //<< I try to use this!
    QVector<float> times;
    times.append( 0.0f );
    times.append( 5.0f );
    times.append( 8.0f );
    times.append( 12.0f );
    /* vertexBlendAnimation setting */
    animation1->setTargetPositions( times );
    animation1->setTarget( mesh );
    animation1->setMorphTargets( morphTargets );
    /* morphingAnimation setting */
    animation2->setMethod( Qt3DAnimation::QMorphingAnimation::Relative );
    animation2->setEasing( QEasingCurve::OutInCubic );
    animation2->setTargetPositions( times );
    animation2->setTarget( mesh );
    animation2->setMorphTargets( morphTargets );
    //QObject::connect( animation1, &Qt3DAnimation::QVertexBlendAnimation::interpolatorChanged, material,
    //              &Qt3DExtras::QMorphPhongMaterial::setInterpolator );
    QObject::connect( animation2, &Qt3DAnimation::QMorphingAnimation::interpolatorChanged, material,
                      &Qt3DExtras::QMorphPhongMaterial::setInterpolator );
    /* use PropertyAnimation */
    //auto propertyAnimation = new QPropertyAnimation( animation1 );
    auto propertyAnimation = new QPropertyAnimation( animation2 );
    propertyAnimation->setDuration( 5000 );
    propertyAnimation->setStartValue( QVariant::fromValue( 0.0f ) );
    propertyAnimation->setEndValue( QVariant::fromValue( 12.0f ) );
    propertyAnimation->setLoopCount( -1 );
    //propertyAnimation->setTargetObject( animation1 );
    propertyAnimation->setTargetObject( animation2 );
    propertyAnimation->setPropertyName( "position" );
    propertyAnimation->start(); //using animation1 -> ok. using animation2 -> error!?

    view->setRootEntity( rootEntity );
    QMainWindow mainWindow;
    auto container = QWidget::createWindowContainer( view );
    mainWindow.setCentralWidget( container );
    mainWindow.resize( 800, 600 );
    mainWindow.show();

    return a.exec();
}

#include "main.moc"