A Flight Simulator are very, very different from First Person Shooters...
There are many reasons why a flight sim can get away with very large view distances which is mainly down to the ways its been made.
Since your flying most of the time very high above the surface, the surface dose not have to be very detailed, in fact, all the terrain is a low rez heightmap and a colour texture on most of them, very few flight sims bother with detail textures and ones that do have one basic detail texture for the entire map. With a FPS you need very high detailed terrain, so troops can hide in small ditches etc which you will not find on a flight sims terrain. This difference in terrain detail is the first huge difference which means that as such, a flight sim can have the same number of polys in its terrain over 10kms that a normal FPS can have in say under 1km.
The next is objects, buildings can be very, very low detail, basically most of them are simple boxes on a flight sim as your not going to be walking upto the building and knocking on its front door like you do in a FPS. As such you only need the very basic shape of the building, no interior and no small details such as door handles, lights, door steps etc etc. Loading all these high detail meshes and textures into the memory for a FPS also takes up a huge amount of memory and the more things your loading due to a larger VD, the slower the game gets and the more chance the user will run out of memory and CTD.
The next being that because your flying so high up in the sky these buildings most of the time are not even drawing until your right up close to them which is fine as when your that high up the terrain's colour texture is that of a city with lots of buildings so it looks like nothing is missing as your looking strait down on the city. If we where to do the same in a FPS, where your standing on the ground, with no horizon of a city which would significantly impact on the gameplay if you couldn't see a city 2kms away from you and you can't fall back on the terrain's colour texture as your looking perpendicular to it and as such, you can't see the terrains colour at that distance unless its a hill going up but even so, it still wouldn't be enough.
We do have LODs (Levels of Detail) on our models but many of the vBF2 models where never designed to go up to 1km view distances which we have in PR and it isn't really feasible to crate new LODs for these objects without remaking them fully from scratch ourselves. All our stuff we make thou we do try and make as optimized as possible for our view distances but the vBF2 stuff really dose hold us back quite a bit but even with super good LODs, there is still only so much you can pull out of this type of engine.
There are lots of other reasons but thous are the main reasons why a Flight Sim can get away with such high VDs and a FPS can not, other than ARMA2 which its engine uses a different system from most games where it loads everything out of the hard drive rather than the RAM, which means things like building LODs don't switch very quickly when you have a slow HDD but dose mean it can have longer VDs. We with PR:BF2 are working with a 6 year old engine here, the more engines and hardware become more advanced, the more you can do with detail and view distance.
Bluedrake42 wrote:But there are probably clever ways to sidestep these issues? For instance I noticed that ArmA 2 if there are players in "Grass" then they actually merge into the terrain, instead of just sitting on top of it uncovered.
Yes, one clever bit of the ARMA2 engine but something that isn't possible with the BF2 engine.
