Failed to render a OSG pointcloud with normals using QOpenGLFrameBufferObject

[cjmdaixi]

Hi, everyone. I am currently working on a project that connects OpenSceneGraph and Qt Quick, especially to render a pointcloud with normals binding to each vertex. After searching a lot of references and materials, I decided to use QOpenGLFrameBufferObject according to the official example "textureinsgnode". I can now render the vertices in the pointcloud, however, the normals information seem to be missing (The result is a pure white pointcloud). My question is how to get my normals rendered? Some important code snippets are shown below:
//constructing the pointcloud geometry in OSG
geometry->setVertexArray(vertices);
geometry->setNormalArray(normals, osg::Array::BIND_PER_VERTEX);
pointIdx = new osg::DrawElementsUInt(osg::PrimitiveSet::POINTS);
qint64 verticesSize = vertices->size();
for (size_t i = 0; i < verticesSize; ++i)
pointIdx->push_back(i);
geometry->addPrimitiveSet(pointIdx);

//constructing the framebufferobject in osgQuickRenderer.cpp
QOpenGLFramebufferObject *osgQViewerRenderer::createFramebufferObject(const QSize &size)
{
qDebug()<<"create framebuffobject "<<size.width()<<"x"<<size.height();
QOpenGLFramebufferObjectFormat format;
format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
format.setSamples(4);
return new QOpenGLFramebufferObject(size, format);
}

What am I missing? Any suggestion would be appreciated, thanks!