Premise: reducing polygons, particle effects, animations, vertices to be shaded, and pixels which need to be shaded -> reduced graphics load
Premise: reducing the number of rate of production, consumption and transport calculations -> reduced CPU load
Premise: buildings (walls, foundations and ceilings) can be used to completely* enclose some set of factory components, and this enclosure can be detected programatically.
Idea: encapsulate enclosed subsections into logical units to reduce graphical and CPU load.
This idea is perhaps best illustrated using a common example. Imagine I have an iron ore miner which outputs to a belt at 240 ore/min, which in turn is consumed by, say, 8 smelters which are built on a connected set of foundations. The smelters are producing iron ingots which are merged into a single output belt carrying ingots at 240/minute.
I then completely* enclose those smelters with walls and a ceiling made of foundations.
What I now have is a single logical unit which takes ore as input, and produces ingots as output, with the conversion rate and total power consumption defined by a fairly simple set of rules. I will temporarily refer to this unit as an "encapsulated factory building", or "EFB".
At this point, there is no longer any need for the game to calculate all production components inside the EFB individually. Furthermore, as long as I am standing outside the EFB, there is no need for the game to render anything going on inside.
Now, I put an asterisk on the word "completely" before. Why? Well, because obviously there need to be "holes" of some kind in the EFB, ie, places where the belts can get in and out. These holes are provided by the conveyor walls, and I can see through those holes. So if we stopped rendering everything inside, and changed nothing else, it would look weird.
So, in order to make this work nicely something else should be changed. I suggest that if the player chooses to "encapsulate" a subsection of production in this way, all of the "holes" created by conveyor walls, doorways, and so on, be filled by a simple opaque black texture. A player could still walk through a doorway into the EFB, and once inside the game would need to render all of the machinery again - but at the same time, it could *stop* rendering anything going on outside the EFB.
To some degree this rendering optimization is already provided by techniques like occlusion culling. But deciding whether polygons should be rendered or not based on occlusion culling is itself a non-trivial (ie, somewhat expensive) operation. it is *far* faster to simply assert that an entire object doesn't need to be rendered, such that no polygons for the object even enter the rendering pipeline in the first place, no particle effects generated by the object even need to be considered, and so on.
If the player removes any wall, floor, or ceiling, or alters the internals of the EFB, then the encapsulation would be undone and all individual components would be processed as normal until the player "re-encapsulates" the building.
This would provide a truly gigantic performance boost when factories grow large.
