Thursday, November 15, 2012
I've written about refining the D&D archery rules a few times, in regards to indoors ballistics and normalized probabilities (e.g.: here, here, and here). A while ago I again looped back to thinking about them, because a few parts of the prior stuff I've written have started to bother me. Here's the revised rule what I've been using for a while now:
Bows: Bows can be fired every round; slings and crossbows every other round. Indoors, all missile weapons have an effective range of 6"/12"/24" (30/60/120 feet; assume a 10' ceiling). Attacks are +4 at short range, +2 at medium range.
Throwing: A spear, dagger, or hand axe may be thrown up to 12" (60 feet) indoors. These are always treated as long range (no bonus to hit).
Long Distance: High ceilings allow longer bowshots, but these are at -10 to hit individual targets. Shots at great distance outdoors are only effective against armies or the like.
Commentary: The primary issue that drove the change is as follows. Even with the modifications I've suggested in the past, I was still trying to hang on to the hand-wavy system in D&D that you can arbitrarily switch from scales in tens-of-feet (indoors) to scales in tens-of-yards (outdoors) and still use the exact same range modifiers. In retrospect, that's unsustainable, and I'm going to stop using it; different scales simply must recognize different chances to hit. (This would be one of the "distortions" mentioned by Gygax in Dragon #15 [todo: link], and one that most later systems sensibly avoided.)
Let's think about why that was done in the first place. Again, the scale 1" = 10 yards was originally established for historical, mass-combat Chainmail, and in so doing, created realistic scaling for mass figures, movement rates, and bowshots on the tabletop. Later, 1" = 10 feet was used by Arneson in his man-to-man games, and included by Gygax in D&D as the "underworld" scale (Vol-3, p. 8), with 1" = 10 yards maintained as "wilderness" scale (Vol-3, p. 17). But there are two major problems with this retention. First, the 1" = 10 yards scale is less about being outdoors, and more about the mass-combat scale, and so irrelevant for the man-to-man RPG. Second, while it enables a realistic-length bowshot outdoors, it overlooks a colossal and critical fact -- no one in the world can possibly hit a single man at maximum distance with a longbow. Hitting an army in formation, yes, easily so; hitting a single man, no, not even close. And hence this consideration is also irrelevant, and even permitting it is one of the "proud nails" that will irk many about the system for years to come.
So let's agree to abandon the separate scale for outdoors action, and consider some physics for a better rule: Due to the inverse-square-law, if we were being really honest, range categories should work by doubling the distance in each category -- in fact, you see this in a lot of gun-based systems like Boot Hill, Star Frontiers, etc. The D&D system (splitting ranges into equal thirds, linearly) is an outlier in that regard, and just plain incorrect. The best I can figure is that, taking a shot of about 40 yards as a base, every halving or doubling of distance should modify to-hits by about +/-8 on a d20 roll (for example: look at the expert archery table we made before; compare the chances shown at 80 yards and 160 yards; 76%-30% = 46%, i.e., 46%/5% = -9 in that case). Technically this modifier should be applied on our normalized table, but in the meat of the progression it's the same as standard D&D.
Now, it's good to be aware of the correct real-world success chances involved; but at the same time, it's best to take those insights and massage them into easy-to-use, highly memorable mechanics that are convenient at the table. What we've calculated in the past for indoor missile ballistics is a 150' maximum shot for basically any weapon under a 10' ceiling (see here). But I figure it's nice and simple to smooth it out to 120', and so have the range in inches revert back to our familiar multiples-of-three: 6"/12"/24". Also, this happens to line up perfectly for range in inches indicated for the heavy crossbow weapon (the longest in the game). And also the 30' lower limit is the same as that identified in AD&D Unearthed Arcana as "point blank range" (UA, p. 18). And also our bonuses are like those in man-to-man Chainmail/OD&D, except doubled for the conversion factor we agreed on in the past (here). So I think there's a lot in favor of this simple setup.
The scale and the mechanic will be used identically both indoors and out (removing one of the "distortions", as Gygax put it). We observe that single men simply cannot be hit by a bowshot outdoors at hundreds of yards distance. If an indoor area has a very high ceiling (cavern, giant-hall, etc.), then allow a shot perhaps up to 48" (240 feet), but at a massive -10 penalty. For simplicity, the same range rule is used for any missile weapon in the game (presenting something easy to memorize, and reflecting again that range of the weapon has little or no bearing on accuracy against a man-to-man target).
Below are some ideas for optional rules you might also consider using in conjunction with this rule.
Optional -- Other Penalties: The scores above assume best-case conditions. Be sure to apply other penalties for darkness or low-light, cover and obstructions, and possibly high-speed movement lateral to the shooter's field of fire. (See Lakofka article in Dragon #45, for example.)
Optional -- Weapon Variation: If you want to treat various weapons differently for indoor, man-to-man combat, then split ranges in inches into thirds as customary, and apply the +4/+2/+0 bonuses as shown above. For example: a longbow will be 7"/14"/21" (35/70/105 feet). This is not totally accurate, but fairly close, simple, and playable (although not so simple as the unified ranges above).
Optional -- Longer Shots: If you want to permit very long-range shots outdoors against man-size targets, keep in mind that this will be an epic feat achievable only by very high-level warriors. Longer shots can be allowed outdoors at ranges up to 50"/100"/200" (i.e., 250/500/1000 feet, or about 80/160/320 yards), at to-hit penalties of -8/-16/-24, respectively. Of course, the standard maximum range of the missile weapon still applies.
Optional -- Shots at Groups: While I'm thinking about it, here's a possible rule for shots at groups of size N. Step 1: Identify a target for the shot by random method. Step 2: Roll d20 to hit, but as long as the natural die-roll is less than or equal to 4×log2N, then re-roll any miss. See here for the exact upper bound: N=1:0, 2:4, 4:8, 8:12. (The basic observation here, again based on the inverse-square-law, is that each doubling of range category is balanced by each quadrupling of area/people in the group, i.e., +/-8 to hit. Therefore each doubling of people should be effectively half this, or +4. I don't actually do this, but perhaps you'd like to try it.)