Combat, Part 3: Notes From the Real World
by Travis S. Casey
Many games strive for some level of realism in their combat. All sorts of "realistic" factors get thrown in, including such things as fatigue, loss of combat effectiveness after taking hits, fighting less well when carrying a load, and so on.
The fundamental physics of combat are simple. Such things as weapon weights, the speed with which weapons move when swung, and the kinetic energy they carry are all simple to measure. What is neither simple nor well-understood is how these things interrelate in the mesh of combat.
It's hard to talk about combat without some sort of frame of reference to help make sense of things. For this initial discussion, I'm going to use a traditional paper RPG-style combat system as a frame of reference. This isn't to say that such a system is the best way to approach things, however, and later on, I'll talk about non-traditional combat systems.
Traditional RPG combat systems have parts to handle three major things:
Let's start in the middle, with hitting. What are the factors that determine whether or not a blow hits? Well, the first thing we have to do is determine what constitutes a "hit". The intuitively obvious answer is that any blow which strikes the opponent is a "hit". There's an immediate split here, between those who count only a blow which "damages" the opponent him/her/itself, and those who count blows which strike the opponent's armor. ("Damages" being in quotes because we haven't gotten into what constitutes "damage" yet.)
The various versions of D&D generally count only blows which damage the target as hits and therefore, armor makes a target "harder to hit", since blows which strike the armor but do not damage are not "hits". Many other games count any blow which strikes the opponent or his/her armor as a "hit" and therefore take the point of view that armor absorbs damage instead. Which is better? Well, that depends on the kinds of attacks present in the game (e.g., are there any attacks which should ignore at least some kinds of armor), and on the kinds of armor used "hard" armors can outright stop many blows, while flexible armors will often let some "damage" through. It also depends on the sorts of weapons used if, for example, rapiers and daggers are pretty much the only weapons used, treating armor as simply stopping attacks makes a lot more sense than it does if clubs, maces, halberds, and other such battlefield weapons are common.
All of which takes us to the subject of damage. A simplistic point of view, taken by a few games, is to use kinetic energy of attacks as a measure of their damage potential. In the real world, kinetic energy is used by the military as an important measure of the damaging capability of bullets, which lends it a certain credibility but when used for melee weapons, it ignores the fact that one can continue to "push" the weapon after the point of contact. A simple thought experiment should show how wrong rating melee attacks purely on kinetic energy is:
Imagine taking a knife and lightly throwing it point-first at a person. Then imagine taking the same knife, walking up to the person, placing the tip against him/her, then slowly pressing it into the person as far as you can.
It should be obvious that the second procedure is likely to do more damage than the first. Unless the knife hits a bone on the way in, one can push it in quite far. The kinetic energy of the second knife is at no point as high as the kinetic energy of the first knife was at the point it contacted the target, but the continuing application of force nonetheless allows it to do a greater amount of tissue damage.
That's not to say that energy is not a factor pushing a weapon through tissue is work, in the physics sense, and therefore, the amount of tissue damage possible is dependent on the energy of the blow. However, with a melee weapon, one can continue to supply energy after the point of initial contact, which is not possible with most missiles. (It should be noted that even academic studies fall prey to this error. Gabriel and Metz's mostly excellent From Sumer To Rome: The Military Capabilities of Ancient Armies is an example.)
A second major factor in the effects of a blow is where the blow strikes. The same hit delivered to the side, the forearm, the leg, or the head may have very different effects. For penetrating wounds, even a shift of a few inches may make a major difference e.g., between a thrust through the heart, one through a lung, or one which manages to barely miss both heart and lungs.
In theory, the location of a blow is easy to account for; in practice, it's complicated by such things as angles of entry, the fact that projectiles passing through the body do not necessarily follow a straight path, and the fact that different people can have different arrangements of their internal organs. And that's leaving out the fact that games often need to deal with creatures other than humans a hit location system which deals with humans just fine may need significant changes to deal with a human fighting a giant (e.g., to handle the fact that a six-foot-tall human with a three-foot-sword can't possibly hit a twenty-foot-tall giant in the head if both are standing on level ground. Well, maybe if he decides to throw the sword...) When you start throwing in things like horses, dogs, and snakes, you need to add considerably to the system. Throw in centaurs, dragons, giant worms, and giant centipedes, and things get really fun!
And there are other, less tangible factors involved in damage. Some people just seem to handle injury better than others, independent of any physiological reason for it. And even damage which one would think would be instantly lethal can sometimes be survived. Viewing The Learning Channel's series Trauma: Life in the ER, which films actual patients in actual emergency rooms (not made-up stories or "dramatic recreations"), I once saw an episode in which a man was brought into an ER with a knife stuck in his head. The blade had penetrated the skull and was lodged a good five inches deep in his head, completely penetrating the brain. The victim was conscious and coherent when brought in, and survived the incident with no noticeable loss of function. But if something like that happened in a game, no one would believe it!
While we're on a roll, we'll toss in a fourth factor: adrenaline. In the heat of combat, people have been known to not even notice serious injuries until they are out of danger. Some things can't be ignored, obviously running on a leg which is broken clean through just isn't possible. Shock and pain, however, often can be ignored until one is out of danger. This stands in contrast to the quick "death spirals" of many RPGs, where characters quickly lose effectiveness as they take damage.
Initiative is simultaneously simple and very complex. With all things being equal, the first person to try to attack should be the first person with a chance of landing a blow. Unfortunately, all else is rarely equal... and even when other factors are ignored, how does one decide who the first character to attack should be? (Note the emphasis here a player might decide to attack, but that doesn't necessarily mean that his/her character can right then.)
In some circumstances, initiative is obvious in an ambush or other surprise attack, for example. In other situations, however, things are much less clear. Paper RPGs usually base initiative on Agility, Dexterity, or some equivalent character ability. In truth, though, unless one is dealing with superhumanly fast reaction times, factors of training or psychology may make much more sense to use for initiative determination.
What does a "typical" combat look like? Well... that depends, really, because there's more than one type of combat. So join me in two weeks for a look at types of combat!