Quote Originally Posted by Agent Smith
I've noticed this too, and it might be part of the problem that the OP is getting at. Some artillery have maximum and minimum angles of fire. For instance, if you are on top of a mountain that is really steep and the enemy is below and has catapults, they will NEVER be able to fire at you because the angle is too steep and a catapult can't really release it's ammo at a different point to get the correct trajectory. Same goes for some artillery at the top of hills, too, where the trajectory would no longer be able to effectively target troops that are too steeply downhill.
That's probably it - the firing angles. Most projectiles (see descr_projectiles.txt) do not allow much of a downward angle at all: usually -15 for anything except arrows. Thus if you have cannons for instance planted too high on a hilltop, there can be a rather large area surrounding the hill that the cannons would be entirely unable to shoot. The shots go at a particular speed (not variable like arrows are), and the small declination allowed (and corresponding small downward vertical component of movement on the shot) just don't allow the shots to go anywhere near the cannon's elevated position - they are forced to sail far away. For instance in 1 second, the cannonball can fall 28.2 m if fired optimally downward (-15 degrees). In that same 1 second, it travels ~87 m horizontally. That's about a 3:1 ratio, meaning after 1 second the ball has flown 3 times further horizontally than it has dropped vertically. I'm sure you can see why that would be problematic and leave a large area surrounding any elevated artillery position where the artillery simply cannot fire.

As for determining the effect in-game, estimating an area 3 times longer than the height of the hill is probably a good ballpark guess at the closest point where your artillery coverage will be effective.

A related problem lies in the artificial limiting of a cannon's range to an amount far shy of what it's projectile stats would allow. A bombard even on flat ground could shoot out to 715 m within its parameters, but is only allowed to shoot 325 at most by the EDU, which really trivializes the usefulness of high ground to it except that it gets some cleaner sight lines. Thus a substantially elevated position, instead of granting the artillery greater reach, only serves to cut off a huge portion of its targetable area, leaving a fairly narrow ring that it can successfully target, bordering and including its max 325 range. The best solution is probably to set the cannon shot to a lower velocity that gives a flat range more in the 325 ballpark. That lower velocity would then be used as the upper bound on firing range, not the EDU range (which would increase so as to not be a factor). That would actually allow elevated positions to correctly increase artillery range, and would also provide the artillery somewhat better capability to shoot downward (due to less velocity to push the shot out and away) though it will be marginal at best.

If I've done the figuring right, a velocity of 60 gives the bombard a max range of ~318 naturally, and something in that vicinity is likely a good value to use for it. Coupled with the lengthening of the EDU listed range, it would then get better use out of a hilltop position by actually being allowed to fire out to the extended range the elevated terrain naturally affords it...