Use vtk.js to render point clouds, why dynamically update one point will not display normally, update two or more points can display normally

Web vtk.js
1

Here’s an example：

const points = vtkPoints.newInstance();
const polyData= vtkPolyData.newInstance();
const polyDataActor = vtkActor.newInstance();

polyData.setPoints(points);

sphereSource = vtkSphereSource.newInstance({
    radius: 0.25,
    phiResolution: 10,
    thetaResolution: 10,
});

polyDataMapper = vtkGlyph3DMapper.newInstance({
    orient: false, 
    scaling: false, 
    scaleMode: vtkGlyph3DMapper.ScaleModes.SCALE_BY_CONSTANT,
});

polyDataMapper.setInputData(polyData, 0);
polyDataMapper.setInputConnection(sphereSource.getOutputPort(), 1);

polyDataActor.setMapper(polyDataMapper);
polyDataActor.getProperty().setPointSize(5);

points.insertNextPoint([435,50,180]);

points.dataChange();
polyData.modified();

renderWindow.render();

Why can’t the point be rendered when dynamically adding a point? When dynamically adding two points, it can be rendered normally.

points.insertNextPoint([435,50,180]);
points.insertNextPoint([438,50,181]);

There is another question, why not render the out-point cloud when the z coordinate value of multiple points is the same, only add 0.00001 to the z value of a point to render the out-point cloud：

points.insertNextPoint([435,50,180]);
points.insertNextPoint([438,50,180]);
2

Does anyone pay attention to this problem? When the z coordinate of the point cloud is the same, the point cloud will always fail to render