As Kylotan says, you start by just loading everything up at program start. Caveman 3.0 does this. I believe Rome II Toal War does as well. if that starts taking forever, you go to loading a level at a time, like dungeons in Skyrim. If that's too big and will take too long, you switch to loading levels / areas / chunks in the background, like skyrim when out in the wilderness.

demand load paging of assets is another option. can work well with predictive background loading. but occasionally you get a cache (texture memory pool) miss, and your render speed drops to that of your hard drive as Kylotan says. this can mean the difference between playable on a bleeding edge PC, and unplayable on a low end rig.

load at program start. if it gets slow, try optimizing it first. binary fread_nolock() is VERY fast. slow load times are often the result of inefficient file formats. that's why many games use their own custom formats with just what they need and nothing more. some of those custom formats have gone on to become de-facto industry standard formats.

I believe Rome II Toal War

Do you have any source material for this? (I am an RTS fan and am always interested in code examples/discussions ESPECIALLY for the Total War series)

Do you have any source material for this?

based on program behavior.

there is a load screen at program start, then a main menu, then a loading game screen, and your in. since its not a level based game, you need more or less all the graphics at once. also, come to think of it, when i would run it on my old PC, it would page assets off the hard drive. so it probably reverts to demand load paging if there's not enough ram to load all the assets upfront. it was so slow on the old PC, i gave up and bought shogun2.