proposal for missile mechanics

[saarn]

I was thinking about why missile weapons are not so great in v4 and a few things came to mind:
1) finesse bonus for melee manifests as multiple blows. This doesn't make sense for missile combat
2) bonuses for v4 are largely based on critical hits. This makes missile damage very uneven (4 rounds of barely scratching a monster followed by great hit and it loses half its HP)

I started thinking about what my ideal missile combat system would have as properties and came up with a few:
1) handle both missile weapons and throwing
2) distinction in "feel" between types of launchers to reflect the difference in mechanism (and indeed use historically). For example, the long bow required considerably more training than the crossbow to use effectively, but was a superior weapon given the right training.
3) bonus to prowess on the weapon or ammo makes it noticeably better
4) hitting enemies further away takes greater skill
5) point blank shooting has a high chance of failure (pet peeve)


What I'd like to suggest is this:
Make damage a function of kinetic energy, accuracy of blow, and missile type. Kinetic energy is mass * velocity^2, so we need some way of determining velocity. For a thrown item, the only factors should be the character's prowess, their throwing skill, and the mass of the item.

For a launcher, you need some sort of representation of the mechanical advantage the launcher gives. This would be some kind of simple piecewise function where below a certain input power the launcher misfires, and past a certain input power there's no further gain. A crossbow for example, should look like a step function. They typically have a ratcheting mechanism, so you either succeed in cocking the weapon or fail-- you can't make it go any harder by being beefy. A bow would look like a ramp that flattens out-- if you pull hard enough to bend the weapon, you can shoot, but there's a limit to how far you can draw the bow since you don't want to snap it. A sling can shoot as hard as you like, but doesn't offer nearly the mechanical advantage of either.

I'm envisioning that the input power in all these cases would be a randomized function of your character's prowess excluding the bonuses on the launcher and missile and shooting ability (based on race/class).

Assuming the minimum energy was reached to avoid a misfire, any bonuses from the launcher or ammo to prowess would be added to the output energy (this would make a +prowess crossbow have higher output damage than a regular one, rather than a higher chance of success).

There would then be a curve for damage as a function of accuracy (past some amount of error left-right you miss, in between maybe have a triangle function where no error is max damage). Both the player and the weapon would have error generated from a normal distribution. The player's SD would be governed by finesse and bow skill, while the weapon's would be governed by type (so crossbow might have higher error than longbow, and heavy crossbow most error). Error terms should be signed so that weapon inaccuracy can sometimes counteract player inaccuracy. Error should be increased as a function of distance, monster evasion, and shot speed (higher speed projectiles should be less affected by distance and evasion). Ideally, it would be possible to aim for one monster and hit something to the left or right if your aim was bad enough, but I suspect that's a much trickier refinement.

I think this would meet my list of goals, and the necessary parameters would be easy to encapsulate in the weapons file as there'd be only four per launcher (min input power, max output power, advantage, accuracy). But as described, it doesn't feel like a D&D rooted solution (not really big on dice, sort of complicated logic) and doesn't seem like it would lend itself to simple assessment of damage/power. I'm sure there would be a lot of tuning needed, and there are probably wrinkles I haven't thought of, but I also haven't seen any concrete proposals for how missile damage should be reworked either.

What do you all think?

[Derakon]

My general inclination is to go with simple, readily-expressable approaches even if they sacrifice realism. I'd also rather keep the math for missile weapons as close to that used for melee weapons as much as possible. That said, there's certainly room to make the weapons more simulationist, so here's my thoughts:

Let's take a look at what you need to shoot quickly and to shoot powerfully with missile weapons. To be quick, you need to be able to grab ammo, nock it, draw, aim, and release (or appropriate analogues for slings). To shoot powerfully, however, is different for each launcher type:

* For bows, power is a function of the bow's draw weight. But to draw the bow, you also need to be strong -- so there's basically a minimum effective strength to use the bow. As I understand it, more strength past that point has little effect (beyond making it easier to hold the bow drawn so you have less trouble aiming, but I'm not certain going into that level of detail is worthwhile).
* For crossbows, again power is a function of the draw weight. In this case, however, strength determines how quickly you can draw the bow (we can assume that all crossbows have some kind of leverage or ratcheting system, so there's no question of being able to draw the bow if you have enough time). Shot power is constant.
* For slings, power depends directly on your own strength, and, I guess, the weight of the projectile you're using. But we can gloss over that in the interests of simplicity.

This gives us three different formulas for your shots/round, and damage/shot, which can be modified in different ways. Let's keep the "balance" and "heft" attributes from melee weapons, rechristened as "balance" and "draw". And we'll ditch the x2/x3/etc. launcher multiplier entirely.

Bows
Shot speed: (character's missile finesse) * (launcher balance)
Damage: (ammo dice roll) * (launcher draw) * (character's missile prowess) * (ammo prowess)
You take a significant penalty to hit chance, damage, and shot speed if your STR is too low (much like when trying to use an overly-heavy melee weapon). Bows are hard to use properly, but have the best potential damage/round if you have the skill.

Crossbows
Shot speed: (launcher draw)
Damage: (ammo dice roll) * (launcher draw) * (character's missile prowess) * (ammo prowess)
You take a significant penalty to shot speed if your STR is too low. Weapon balance / finesse is only used to calculate hit chance (we can assume that the dexterity needed to load a bolt onto the crossbow quickly is overwhelmed by the time needed to crank the crossbow back, which is why finesse doesn't affect shot speed).

Slings
Shot speed: (character's missile finesse) * (launcher balance)
Damage: (ammo dice roll) * (character's missile prowess) * (ammo prowess)
Slings have weaker damage formulae, but they can be fired rapidly are are easy to use. They have no relevant "draw" characteristic. Later on slings can remain relevant by having high-dice ammo.

[Magnate]

Thanks both - I've been hoping for other people to do the thinking on this!

Bows
Shot speed: (character's missile finesse) * (launcher balance)
Damage: (ammo dice roll) * (launcher draw) * (character's missile prowess) * (ammo prowess)
You take a significant penalty to hit chance, damage, and shot speed if your STR is too low (much like when trying to use an overly-heavy melee weapon). Bows are hard to use properly, but have the best potential damage/round if you have the skill.

Crossbows
Shot speed: (launcher draw)
Damage: (ammo dice roll) * (launcher draw) * (character's missile prowess) * (ammo prowess)
You take a significant penalty to shot speed if your STR is too low. Weapon balance / finesse is only used to calculate hit chance (we can assume that the dexterity needed to load a bolt onto the crossbow quickly is overwhelmed by the time needed to crank the crossbow back, which is why finesse doesn't affect shot speed).

Slings
Shot speed: (character's missile finesse) * (launcher balance)
Damage: (ammo dice roll) * (character's missile prowess) * (ammo prowess)
Slings have weaker damage formulae, but they can be fired rapidly are are easy to use. They have no relevant "draw" characteristic. Later on slings can remain relevant by having high-dice ammo.

This raises a few issues for me.

1. What is "ammo prowess"? If it's like 'heft' for ammo, I think it's redundant - isn't this why different ammo has different dice?

2. I don't like the concept of a STR breakpoint below which you have penalties. I'd rather just reverse the use of fin + prow, so that prow determines your shot speed (speed of drawing/loading) and fin determines your damage (accuracy of shot). As you said, once you've drawn a bow any extra strength doesn't increase the damage from it, so it seems to me that the value of strength (and therefore prowess, in our system) is in speed. (This is for bows and xbows but not slings - for slings I agree that fin and prow can have their usual applications.)

3. I am wondering whether draw ought to be used for bow shots rather than balance, as with xbows. But I don't think I like not using balance - it needs a different name, but I think we should make the same distinction between lots of shots and damaging shots that we do with melee weapons.

4. I don't think we need separate missile prowess. The skill that makes sling shots do more damage is the same as (or at least, sufficiently similar, for our purposes, to) that which makes weapons do more damage - a combination of putting weight behind it in the right direction for maximum damage. (If we use my idea of reversing the applications of fin/prow for bows and xbows then this issue is nicely fudged for them, since missile finesse is different anyway.)

[saarn]

I guess I have a couple concerns with the approach outlined by Derakon (though it feels more similar to other Angband mechanics which is probably a good thing).

1) do we really want multiple shots per round to be a major part of missile combat?
Cons: high ammo burn + 40 missile stacks + absorptive armor will make this a frustrating approach. Especially since high finesse characters are going to have a harder time lugging stacks of ammo around the dungeon and are precisely the ones who need to do relatively high damage from distance. Wouldn't this also completely devalue the ranger extra shot bonus?

2) No story on throwing. I personally really like the idea of a giant half troll warrior with maxed strength being able to kill a monster by throwing a 100lb chest at it.

[Derakon]

1) do we really want multiple shots per round to be a major part of missile combat?
Cons: high ammo burn + 40 missile stacks + absorptive armor will make this a frustrating approach. Especially since high finesse characters are going to have a harder time lugging stacks of ammo around the dungeon and are precisely the ones who need to do relatively high damage from distance. Wouldn't this also completely devalue the ranger extra shot bonus?

I think this is mostly a matter of calibration. But why do you say that the finesse characters are the ones who will need to be able to do damage from a distance? Finesse and prowess characters should be broadly equal in melee; the former have a significant advantage against groups and evasive monsters, while the latter have a significant advantage against absorptive monsters. Are you suggesting that finesse characters should be able to shoot iron golems to death?

In any event, I certainly don't think that multiple shots should show up to anywhere near the extent that multiple blows do, for two reasons. First, it's a pain to have to go pick up all that ammo after every fight; second, breakage becomes a more severe issue for every extra shot you have. I think current Vanilla represents a good target: skilled archers get +1 shot, and very rarely (or with high-level rangers) you get +2 shots, but that's it. Of course, it'll be a smoother continuum (getting e.g. 1.47 shots/round instead of just 1 or 2).

2) No story on throwing. I personally really like the idea of a giant half troll warrior with maxed strength being able to kill a monster by throwing a 100lb chest at it.

I do too, but it's not currently part of Angband so I left it out as a thing we didn't have to do in the first pass. Throwing should be able to be worked into combat as a modification to the basic rules once we have standard missile combat working.

[quote=Magnate]1. What is "ammo prowess"? If it's like 'heft' for ammo, I think it's redundant - isn't this why different ammo has different dice?/[quote]I simply meant the +prowess bonus on the ammo. I recognize that currently this is summed with the bonus on the bow to get a total bonus; my thought was that by multiplying them instead we could get a smoother damage curve for ammunition, slightly less reliant on getting access to better ammo types. I suppose alternately we could do away with finesse and prowess bonuses on ammo altogether. Make their only modifiers be slays and dice manipulation. Then we wouldn't have to deal with summing modifiers any more, while frankly I think ammo would become more interesting.

2. I don't like the concept of a STR breakpoint below which you have penalties. I'd rather just reverse the use of fin + prow, so that prow determines your shot speed (speed of drawing/loading) and fin determines your damage (accuracy of shot). As you said, once you've drawn a bow any extra strength doesn't increase the damage from it, so it seems to me that the value of strength (and therefore prowess, in our system) is in speed. (This is for bows and xbows but not slings - for slings I agree that fin and prow can have their usual applications.)

So then we're assuming that anyone, no matter how noodly their arms are, can use a longbow with a 60-pound draw weight? We already have the concept of weapons that are too heavy to use effectively; why not extend that to bows as well? Are you worried about a double whammy, i.e. characters who cannot fight at all because their STR is too low?

The main issue I have with using prowess to determine shot speed is that it inverts the user's expectations for what (+X, +Y) means. Normally X modifies your speed and Y modifies your damage, but that would be backwards for bows. Why can't we hide the flip from the user? That is, leave X as the speed-modifier, but secretly it's prowess; leave Y as the damage modifier, but secretly it's finesse. This does amount to lying to the user, and might make things a bit hairy code-wise, but at the moment I think it's better that making the display confusing.

3. I am wondering whether draw ought to be used for bow shots rather than balance, as with xbows. But I don't think I like not using balance - it needs a different name, but I think we should make the same distinction between lots of shots and damaging shots that we do with melee weapons.

Bows should require the most skill to use, which means that finesse and prowess need to show up the most often in the equations.

4. I don't think we need separate missile prowess. The skill that makes sling shots do more damage is the same as (or at least, sufficiently similar, for our purposes, to) that which makes weapons do more damage - a combination of putting weight behind it in the right direction for maximum damage. (If we use my idea of reversing the applications of fin/prow for bows and xbows then this issue is nicely fudged for them, since missile finesse is different anyway.)

Fine by me.

[jevansau]

Since this discussion has started up, I also had some thoughts about how archery could work at V4. Not sure if this is better or worse than the previous posts so:
To keep a different feel to slings, bows and crossbows -
slings - have fixed rate of fire - variable damage multiplier (just a heft rating)
crossbows - have fixed damage multiplier - variable rate of fire (just a balance rating)
bows - variable both (balance and heft ratings)

If we want to have a similar system to melee - perhaps include finesse and power from launcher and missile and just exclude melee weapon amounts.

Dice come from the missile, balance/heft from the launcher
Replace the Rangers extra shot with a bonus to balance (getting the most out of the launcher)
Value thoughts:
Sling rate of fire 1 heft .3
Light crossbow balance .15 multiplier 3
Heavy crossbow balance .1 multiplier 4
Short bow balance .2 heft .25
longbow balance .15 heft .3

[Magnate]

I simply meant the +prowess bonus on the ammo. I recognize that currently this is summed with the bonus on the bow to get a total bonus; my thought was that by multiplying them instead we could get a smoother damage curve for ammunition, slightly less reliant on getting access to better ammo types. I suppose alternately we could do away with finesse and prowess bonuses on ammo altogether. Make their only modifiers be slays and dice manipulation. Then we wouldn't have to deal with summing modifiers any more, while frankly I think ammo would become more interesting.

Not yet sure what I think about this. I think consistency is important (see below on your flipping point), and I think adding feels more intuitive to me than multiplying. I haven't thought through the range of numbers each would provide, or why ammo would be more interesting without plusses.

So then we're assuming that anyone, no matter how noodly their arms are, can use a longbow with a 60-pound draw weight? We already have the concept of weapons that are too heavy to use effectively; why not extend that to bows as well? Are you worried about a double whammy, i.e. characters who cannot fight at all because their STR is too low?

No, I just don't like discontinuities. I don't mind STR 11 resulting in lower damage output than STR 12, but the combination of a cliff-edge there and NO difference between 11, 10, 9 ... down to 3 (because they're all too low to use the weapon) feels totally wrong.

(I was thinking about this with melee weapons too - it gnaws at me that weight is now not relevant at all, barring the min STR cliff-edge. I think the simplest solution is for me to make weapon weights proportional (not necessarily linearly) to heft.)

So my thinking is that lower STR means progressively fewer shots, i.e. using prowess in the shots calc. But I see your point that actually for bows the shots should be less effective, not fewer - so maybe we don't need the flip for bows, and stick with prowess for the damage mult, flipping only for xbows. So really weak characters will do less damage with their shots.

The main issue I have with using prowess to determine shot speed is that it inverts the user's expectations for what (+X, +Y) means. Normally X modifies your speed and Y modifies your damage, but that would be backwards for bows. Why can't we hide the flip from the user? That is, leave X as the speed-modifier, but secretly it's prowess; leave Y as the damage modifier, but secretly it's finesse. This does amount to lying to the user, and might make things a bit hairy code-wise, but at the moment I think it's better that making the display confusing.

I hadn't thought of this, and I see the problem. Yes, I think secret flipping is fine - we explain it clearly in the docs, and intuitively it will work fine - the first number affects your blows/shots, and the second affects your damage. The fact that for crossbows it's prow/fin and for everything else it's fin/prow is not a problem.

Bows should require the most skill to use, which means that finesse and prowess need to show up the most often in the equations.

Yes, I see this - but in fact I think slings and bows can safely use the same logic - finesse for loading and aiming, and prowess for putting power behind the shot. So essentially the same model as melee combat, and with ammo dice for arrows being substantially better than for slings. Draw of slings would also be lower than for bows, because they won't ever do quite as much damage (though there's no real reason they couldn't fire as often).

So I think the only anomaly I really want is that fin/prow are reversed for xbows, where prowess determines how quickly you can crank the mechanism and fire. Finesse could determine how well you can place the bolt - but since that duplicates its aiming function (to-hit), we could dispense with that and just have xbows do flat damage - i.e. instead of the 'draw' being a number between 0 and 1 used as a fraction of your own prowess score, like other weapons, it's an absolute value (e.g. 120, 400, whatever) which is then used in the same equation: dice roll * this value (pace whatever happens with ammo prowess).

This means that extremely weak characters will still do decent damage with hxbows but will not fire them often, while warriors and rangers will still have meaningful choices of launcher depending on what they find.

[saarn]

I think this is mostly a matter of calibration. But why do you say that the finesse characters are the ones who will need to be able to do damage from a distance? Finesse and prowess characters should be broadly equal in melee; the former have a significant advantage against groups and evasive monsters, while the latter have a significant advantage against absorptive monsters. Are you suggesting that finesse characters should be able to shoot iron golems to death?

I think anyone should be able to shoot iron golems to death, given a good enough launcher and missiles and enough turns. Most characters will probably find it more convenient though to hack and back them to death.

The reason I think finesse characters are more reliant on pot shotting is two-fold: big monsters tend to have high armor rather than evasion, and finesse characters tend to have lower HP. To compensate, they also generally have unlimited phase door (I am thinking rogue, ranger, and mage).

In my current v4 game I'm playing a hobbit rogue with high finesse and con, I have 206 HP at level 26 and am trying to figure out how to deal with Azog etc. I can't take !speed and hack and back, I can't stand and trade (I'll lose HP as fast as I can quaff !CCW), and missiles are going to bounce. What I would normally do is soften him up and then finish him off once my missiles/mana run low. For a mage, missiles are similarly important for softening up targets as they let you conserve mana.

--- random thoughts follow

I think it would make sense to make prowess the primary governor of rate of fire for all missile launchers and finesse the main factor in damage. You'd have lighter stacks of weapons for finesse characters, they could use missile combat to handle high absorption, and prowess characters could use rate of fire to handle monsters like phase spider with high evasion. Physically, if you are barely strong enough to cock your bow, you shouldn't be able to shoot twice in a round with it, no matter how dextrous you may be.

Possibly slings should be limited to one shot per round but have a very high potential damage output since these would be the only launchers that have an unlimited damage increase from prowess.

It would be good if these control parameters could be embedded in the weapon description rather than hard cases in the code based on launcher type. If a variant (or angband) wants to add in a new type of launcher (say an atl-atl) it seems like it would be better to have a path where that can just work.

I could go either way on base prowess or base strength controlling whether you can shoot or not, but I'd like to suggest making it a roll for a misfire (I saw magnate suggesting reduced shot rate, but I'm not sure how you were planning on implementing shot rate below 1/turn-- would that be a slow action?).

Have you considered modifying range based on launcher prowess?

I like the suggestion that missiles don't have +prow/fin. It makes sense since bows don't get slays.

I think this is sounding like a good direction overall.