for particles there's not too much difference from what fusion does. there is a different particle "engine", sub engine, subroutine, or handler or whatever you want to lable it that is called from the main routine, however it is shader based also, so allot of the shader math is done by the card.
when the mesh renderer draws the triangles for that particular ent it calls upon it's shader reference, which is already in the video card, so it's GPU specific and not engine based. yea some things can be passed over, but the rest is already in the shader script, therefore in the card, when it's first loaded.
i mean think about it. every frame every single thing is wiped on the screen, then sorted and rendered, repeat. since the server (game) determines allot, allot is lerped. for client game (cgame) some stuff is held into memory to lerp, some stuff is spawned all client side and either shoved in memory for retention or destroyed and re-rendered.
its the amout and method of retention that i think is strange for some to think. the renderer engine (executable) is just fed what cgame tells it that it should render; it's up to cgame to handle it all in memory. some stuff just isn't done that way because of time issues and memory issues, performance reasons, hacks.
remember we are talking about a remote server/game and a local renderer/client here. the theory and methods that Id uses are solid and proven, although limited, they work and leave allot of room to expand upon.
Id cannot patent the cgame/game/renderer relationship because it's been around as long as telnet/gui zork, but the concept of destroying and rerendering server-specific ents while maintaining bare-bones data about such things are origins, effects and nothing else has been proven the most stable and expandable concept with online games in history. I doubt it will change, it'll just get leaner and meaner in the future.