I'm sorry to say that I cannot answer this from Revit API slide, the point clouds feature should be internal mechanism of Revit.
You may refer to online help about point cloud here:
http://help.autodesk.com/view/RVT/2018/ENU/?guid=GUID-BD499295-84DD-4BDE-B60D-73008AFBC791
In general, we discuss pure Revit API related issues here in this forum, you will probably obtain more questions and fruitful answers on those issues in the Revit product discussion forum:
https://forums.autodesk.com/t5/revit-architecture-forum/bd-p/133
Thanks for your great understand and patience.