How to use the index of BufferGeometry？

Questions
1 
this._geometry.setAttribute( 'position', new THREE.Float32BufferAttribute( tup[0], 3 ) )
this._geometry.setAttribute( 'color', new THREE.Float32BufferAttribute( tup[1], 4 ) 
this._geometry.setAttribute( 'normal', new THREE.Float32BufferAttribute( tup[2], 3 ) )
var material1 = new THREE.RawShaderMaterial( {
      uniforms: {
        lightPos: { value: this._camera.Camera.position },
        lightColor:{value: new THREE.Vector3(1.0, 1.0, 1.0)}
      },
      vertexShader: modelVertexShader,
      fragmentShader: modelFragmentShader,
      side:THREE.DoubleSide,
    } )
var mesh = new THREE.Points(this._geometry,material1)
this._scene.add(mesh)

Above code:All points can be seen
If index is used,Like this:this._geometry.setIndex( tup[3] ):There’s no point
Another way:this._geometry.index = new THREE.BufferAttribute(tup[3], 1,):Only part of the point can be seen

Why not render all the points？tup[3] is the index of all points. I’ve confirmed it.Its type is uint16array.Do I use it incorrectly？

2

Please demonstrate the issue with a live example. Right now, it’s not clear what’s going wrong in your code.