Accessing particles of SCNParticleSystem class

Sorry, missed that part in the official documentation. Originally I needed that for madifying particles in order to be able to apply postprocessing shaders and transforming individual particles into Metaballs to get "cheap" liquid that responds to physics interactions in 3D. As some of you may know or don't, simulating liquid in 3D is quite expensive task (computationally).

I would relly appreciate if Apple considers my request and allows us, developers to get access to the particles (as a collection, for instance, or maybe some other data structure).