def __node(self):
# this function creates and returns particles' GeomNode
points = GeomPoints(GeomEnums.UH_static)
points.addNextVertices(self.__numPart)
format_ = GeomVertexFormat.getEmpty()
geom = Geom(GeomVertexData("abc", format_, GeomEnums.UH_static))
geom.addPrimitive(points)
geom.setBounds(OmniBoundingVolume()) # always render it
node = GeomNode("node")
node.addGeom(geom)
return node
